This study was funded by Mae Fah Luang University. The authors would like to acknowledge the Tea and Coffee Institute of Mae Fah Luang University for facilitating the connection between the researchers and local farmers concerning the acquisition of coffee silverskin samples.

The details of the reagents and the equipment used in this study are listed in the Table of Materials.
1. Experimental preparation
<ol>
	<li>Plant sample preparation
	<ol>
		<li>Collect fresh coffee silverskin (Coffea arabica) and dry it at 60 &#176;C in a tray dryer for 72 h11.</li>
		<li>Grind the dried coffee silverskin (CS) into a fine powder using a grinder and store it at room temperature for further analysis11. 
		NOTE: In this study, fresh CS (C. arabica) was collected from Baan Doi Chang, Mae Suai District, Chiang Rai, Thailand. CS is a byproduct obtained during the hulling process that removes the parchment layer from dried coffee beans after the cherries have been processed to remove the outer fruit layers16.</li>
	</ol>
	</li>
	<li>Chemicals
	<ol>
		<li>Use chemical reagents of analytical grade quality, except for the solvents in the experiment. 
		NOTE: Cosmetic-grade solvents were used in the experiment.</li>
		<li>Use the solvents (water, ethanol, glycerin, propylene glycol, butylene glycol, hexylene glycol, isopentyldiol, 1-2 hexanediol, pentylene glycol, and methylpropanediol) for the extraction of CS with MAE.</li>
	</ol>
	</li>
</ol>
2. Extraction process
<ol>
	<li>Sample and solvent preparation
	<ol>
		<li>Prepare the sample and solvents for the MAE procedure according to a previously reported protocol9 with some modifications.</li>
		<li>Prepare each solvent at 60% concentration by diluting 60 mL of each solvent with distilled water and adjusting the volume to 100 mL for triplicate extractions. 
		NOTE: Use 100% distilled water for water extraction.</li>
		<li>Weigh 0.67 g of CS and mix with 20 mL of each extraction solvent at a 1:30 ratio in a reaction container (Figure 1A) for MAE. 
		NOTE: The maximum solid-liquid amount for each vessel is 2 g of sample and 20 mL of solvent.</li>
		<li>Add a magnetic stirrer bar to each vessel to ensure uniform distribution of the heat and solvent within the sample, enhancing the efficiency of the extraction process and promoting better extraction yield. 
		NOTE: If nonpolar solvents are applied to the extraction process, Teflon stirrer bars can be used instead of magnetic stirrer bars to deliver effective heating through the microwave system.</li>
		<li>Close each vessel firmly with a special tool (Figure 2) and place all vessels into the MAE chamber (Figure 1B).</li>
	</ol>
	</li>
	<li>Setting up the microwave-assisted extraction instrument and procedure
	<ol>
		<li>Perform the extraction procedure according to the reference protocol with some modifications9.</li>
		<li>Open the monitor screen to set up the method by clicking on the toolbox icon on the top bar and selecting the SK eT rotor in the accessory section (Figure 3A,B).</li>
		<li>Select the stirring rate of the stirrer bars by clicking on the stirrer section and typing 20% (Figure 4A). 
		NOTE: The stirring rate can be selected from 0% to 100%.</li>
		<li>Click on the door lock sector and set it to activate at temperatures exceeding 80 &#176;C (Figure 4B). 
		NOTE: This setting ensures automatic closure of the chamber door when the internal temperature surpasses 80 &#176;C.</li>
		<li>Click on the table icon on the top bar (Figure 5A) and set the temperature gradient (T1) to an extraction duration of 10 min, microwave power to 1800 W, and temperature to 120 &#176;C.</li>
		<li>Activate the stirrer by clicking on the stirrer button until the green light appears.</li>
		<li>Set the blower fan speed to level 3 (maximum) (Figure 5B).</li>
		<li>To hold the extraction time, select the desired extraction temperature (T2) by setting the extraction duration to 15 min, the microwave power to 1800 W, and the temperature to 120 &#176;C.</li>
		<li>Set the stirrer and fan speed as stated in section 2.2.6 and 2.2.7 (Figure 5A,B). 
		NOTE: The maximum temperature and microwave power are 260 &#176;C and 1800 W.</li>
		<li>Set the cooling time by clicking on the cooling button at the lower left corner of the screen and selecting the duration of 10 min (Figure 6).</li>
		<li>Save the method by clicking on the save icon at the top right corner of the screen (Figure 7A).</li>
		<li>Ensure that after saving the method conditions, the extraction conditions graph will be displayed on the screen with the play button in the lower right corner (Figure 7B).</li>
		<li>Start the extraction process by choosing the number of vessels used (Figure 7C). 
		NOTE: Up to 15 vessels can be used in one extraction, and if the desired number of vessels is utilized, ensure the balanced placement of vessels in the chamber.</li>
		<li>Following extraction, centrifuge the extracts at 4 &#176;C, 9072 x g, for 15 min, using a refrigerated centrifuge machine.</li>
		<li>Collect the supernatant with a 10 mL glass pipette (Figure 8) and store it at -20 &#176;C in the freezer for further study. 
		NOTE: Depending on the particle size and density of the plant residue, the extracts will require longer centrifugation times (20-30 min).</li>
	</ol>
	</li>
</ol>
3. Determination of phenolic compounds
<ol>
	<li>Determination of total phenolic content
	<ol>
		<li>Determine the total phenolic content of the CS extracts by referencing the protocol with some modifications17.</li>
		<li>Prepare a 10-fold dilution of samples by diluting with distilled water.</li>
		<li>Mix 10 &#181;L of the diluted sample with 20 &#181;L of undiluted Folin-Ciocalteu&#39;s reagent and allow them to react for 3 min.</li>
		<li>Next, add 100 &#181;L of 7.5% Na2CO3 solution to the mixture in each well of a 96-well plate.</li>
		<li>Prepare different concentrations for the gallic acid standard concentration range (please see Table 1 and Table 2) by diluting with distilled water.</li>
		<li>Mix them with 20 &#181;L of Folin-Ciocalteu&#39;s reagent and allow them to react for 3 min.</li>
		<li>Next, add 100 &#181;L of 7.5% Na2CO3 solution to the mixture in each well of a 96-well plate.</li>
		<li>Incubate the reaction for 30 min in the dark at room temperature.</li>
		<li>Measure the absorbance of the reaction solution at 765 nm using a microplate reader (Figure 9A).</li>
		<li>Plot the standard calibration curve using the concentrations of the standard and absorbance at 765 nm (Figure 10A).</li>
		<li>Express the results as mg of gallic acid equivalent (GAE) per g of the sample, and calculate using the following equation18: 
		NOTE: mg of gallic acid equivalent (GAE) per g of sample = [((A765 - c) / m)) in &#181;g gallic acid equivalent &#215; Total volume in reaction well (mL) x Dilution &#215; weight of dry sample (1 g) x Resultant volume of extract (mL)] / [(Volume of sample added into each well (mL) x Actual weight of dry sample (g) &#215; conversion factor from &#181;g to mg (1000)] 
		&#8203;where, c = y-intercept, m = slope</li>
	</ol>
	</li>
	<li>Determination of the total flavonoid content
	<ol>
		<li>Determine the total flavonoid content of the CS extract according to the protocol with some modifications17.</li>
		<li>Prepare a 5-fold dilution of samples by diluting with distilled water.</li>
		<li>Add 50 &#181;L of the diluted sample to 15 &#181;L of 5% NaNO2 and incubate in the dark for 5 min.</li>
		<li>Mix 15 &#181;L of 10% AlCl3 solution with the reaction and keep it at room temperature for 6 min.</li>
		<li>Then, add 100 &#181;L of 1 M NaOH solution to the reaction and incubate for a further 10 min.</li>
		<li>Measure the absorbance of the mixture at 510 nm (Figure 9B).</li>
		<li>Prepare different concentrations of quercetin standard range (please see Table 3 and 4) by adding them to 15 &#181;L of 5% NaNO2 and incubating in the dark for 5 min.</li>
		<li>Mix 15 &#181;L of 10% AlCl3 solution with the reaction and keep at room temperature for 6 min.</li>
		<li>Add 100 &#181;L of 1 M NaOH solution to the reaction and incubate further for 10 min.</li>
		<li>Determine the absorbance of the standard at 510 nm (Figure 9B).</li>
		<li>Plot the standard calibration curve using concentrations of the standard and absorbance at 510 nm (Figure 10B).</li>
		<li>Express the results as mg of quercetin equivalent (QE) per g of the sample, calculated by equation19 as follows: 
		NOTE: mg of quercetin equivalent (QE) per g of sample = [((A510 - c) / m)) in &#181;g quercetin equivalent &#215; Total volume in reaction well (mL) x Dilution &#215; weight of dry sample (1 g) x Resultant volume of extract (mL)] / [(Volume of sample added into each well (mL) x Actual weight of dry sample (g) &#215; conversion factor from &#181;g to mg (1000)] 
		where, c = y-intercept, m = slope</li>
	</ol>
	</li>
</ol>
4. Determination of the antioxidant activities
<ol>
	<li>1,1-Diphenyl-2-Picryl-Hydrazil (DPPH) radical scavenging assay
	<ol>
		<li>Determine the DPPH radical scavenging activity of CS extract according to the protocol with some modifications17.</li>
		<li>Prepare a 10-fold dilution of the samples by diluting them with distilled water.</li>
		<li>Mix 20 &#181;L of the diluted samples with 135 &#181;L of 0.1 mM DPPH solution.</li>
		<li>Prepare different concentrations of the Trolox standard concentration range (please see Table 5 and 6) by mixing with 135 &#181;L of 0.1 mM DPPH solution.</li>
		<li>Incubate the mixture in the dark at room temperature for 30 min.</li>
		<li>Measure the absorbance of the resultant at 517 nm (Figure 9C).</li>
		<li>Plot the standard calibration curve using concentrations of the standard and&#160;% inhibition (Figure 10C).</li>
		<li>Calculate the&#160;% inhibition of the DPPH assay as follows: 
		%&#160;Inhibition = [(absorbance of control &#8722; absorbance of sample)/ absorbance of control] &#215; 100</li>
		<li>Express the results as mg of the Trolox equivalent antioxidant capacity per g of the sample, calculated by the following equation20: 
		NOTE: mg of Trolox equivalent (TE) per g of sample = [((% inhibition-c) / m) in &#181;g Trolox equivalent &#215; Total volume in reaction well (mL) x Dilution &#215; weight of dry sample (1 g) x Resultant volume of extract (mL)] / [(Volume of sample added into each well (mL) x Actual weight of dry sample (g) &#215; conversion factor from &#181;g to mg (1000)] 
		&#8203;where, c = y-intercept, m = slope</li>
	</ol>
	</li>
	<li>2,2&#8242;-Azino-Bis-3-Ethylbenzthiazoline-6-Sulphonic acid (ABTS) radical scavenging assay
	<ol>
		<li>Determine the ABTS radical scavenging activity of CS extract using the protocol from the reference with some modifications17.</li>
		<li>Prepare the ABTS&#183;+ stock solution by mixing 7 mM ABTS and 2.45 mM potassium persulfate (1:2) and incubate in the dark at room temperature for 16 h.</li>
		<li>Prepare the working solution by mixing 5 mL of ABTS&#183;+ stock solution with 100 mL of deionized water.</li>
		<li>Mix 160 &#181;L of ABTS&#183;+ working solution with 10 &#181;L of the 10-fold diluted sample or Trolox standard at different concentrations (see Table 7&#160;and Table 8).</li>
		<li>Incubate the reaction in the dark at room temperature for 30 min.</li>
		<li>Determine the absorbance of the mixture at 734 nm (Figure 9D).</li>
		<li>Plot the standard calibration curve using concentrations of the standard and % inhibition (Figure 10D).</li>
		<li>Calculate % inhibition of the ABTS assay using the following formula: 
		%&#160;Inhibition = [(absorbance of control - absorbance of sample) / absorbance of control] &#215; 100.
		<ol>
			<li>Express the results as mg of the Trolox equivalent antioxidant capacity per g of the sample, calculated using the following equation21: 
			NOTE: mg of trolox equivalent (TE) per g of sample = [((%&#160;inhibition - c) / m)) in &#181;g Trolox equivalent &#215; Total volume in reaction well (mL) x Dilution &#215; weight of dry sample (1 g) x Resultant volume of extract (mL)] / [(Volume of sample added into each well (mL) x Actual weight of dry sample (g) &#215; conversion factor from &#181;g to mg (1000)] 
			&#8203;where, c = y-intercept, m = slope</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Ferric Reducing Antioxidant Power Assay (FRAP)
	<ol>
		<li>Determine the ferric-reducing antioxidant activity of CS extract according to the protocol with some modifications17.</li>
		<li>Prepare the FRAP reagent using a 30 mM acetate buffer at pH 3.6, which is a mixture of 10 mM TPTZ solution in 40 mM HCl and 20 mM FeCl3.6H2O solution at a ratio of 10:1:1.</li>
		<li>Place the FRAP reagent into an amber bottle until required. 
		NOTE: Ensure the FRAP reagent is brown. If contaminated by metal ions or other reactive compounds, the reagent will turn purple and must be discarded. Use only freshly prepared reagents.</li>
		<li>Prepare a 5-fold dilution of the samples by diluting them with distilled water.</li>
		<li>Add 10 &#181;L of the diluted sample or 20 &#181;L of FeSO4.7H2O at different standard concentrations (Table 9 and Table 10) to 180 &#181;L of the FRAP solution.</li>
		<li>Incubate the reaction at room temperature for 4 min.</li>
		<li>Evaluate the absorbance of the mixture at 593 nm (Figure 9E).</li>
		<li>Plot the standard calibration curve using concentrations of the standard and absorbance at 593 nm (Figure 10E).</li>
		<li>Express the results as mg of FeSO4 per g of the sample, calculated using the following equation21: 
		NOTE: mg FeSO4 equivalent (Fe (II) E) per g sample = [((A593 - c) / m)) in &#181;g FeSO4 equivalent &#215; Total volume in reaction well (mL) x Dilution &#215; weight of dry sample (1 g) x Resultant volume of extract (mL)] / [(Volume of sample added into each well (mL) x Actual weight of dry sample (g) &#215; conversion factor from &#181;g to mg (1000)] 
		&#8203;where, c = y-intercept, m = slope</li>
	</ol>
	</li>
	<li>Perform all assays (TPC, TFC, DPPH, ABTS, and FRAP) of each sample in triplicate. In this study, water was used as the blank for most assays, except DPPH, where ethanol served as the blank to address background absorbance.</li>
</ol>
5. Statistical analysis
<ol>
	<li>Use SPSS software to carry out a statistical analysis of the experimental data.</li>
	<li>Conduct the normality test using the Shapiro-Wilk test.</li>
	<li>Compare the bioactive substances and antioxidant activities of polyols-based MAE CS extract and conventional solvents-based MAE CS extracts using one-way ANOVA with Duncan&#39;s multiple range tests.</li>
	<li>Express all data as mean &#177; SD (n = 3) and define the significance level at p &#60; 0.05.</li>
</ol>

Polyol-Based Microwave-Assisted Extraction for Phenolic and Antioxidant Yields

<ol>
	<li>Wawoczny, A., Gillner, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+most+potent+natural+pharmaceuticals,+cosmetics,+and+food+ingredients+isolated+from+plants+with+deep+eutectic+solvents.">The most potent natural pharmaceuticals, cosmetics, and food ingredients isolated from plants with deep eutectic solvents.</a> J Agric Food Chem. 71 (29), 10877-10900 (2023).</li><li>Syukur, M., Prahasiwi, M. S., Yuliani, S., Purwaningsih, Y., Indriyanti, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Profiling+of+active+compounds+of+extract+ethanol,+n-hexane,+ethyl+acetate+and+fraction+ethanol+of+star+anise+(Illicium+verum+hook.+F.)+and+determination+of+total+flavonoids,+total+phenolics+and+their+potential+as+antioxidants.">Profiling of active compounds of extract ethanol, n-hexane, ethyl acetate and fraction ethanol of star anise (Illicium verum hook. F.) and determination of total flavonoids, total phenolics and their potential as antioxidants.</a> Sci Technol Indones. 8 (2), 219-226 (2023).</li><li>Supjaroenporn, C., Khongcharoen, P., Myo, H., Khat-Udomkiri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studying+the+optimization,+characterization,+and+antioxidant+activities+of+phenolic+extracts+extracted+from+Rhus+chinensis+Mill.+Leaf+using+microwave-assisted+extraction+system+with+glycerol+as+a+green+solvent.">Studying the optimization, characterization, and antioxidant activities of phenolic extracts extracted from Rhus chinensis Mill. Leaf using microwave-assisted extraction system with glycerol as a green solvent.</a> Curr Bioact Compd. 20 (3), 68-82 (2024).</li><li>Gasser, M. S., Abdel Rahman, R. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sustainability+of+solvent+extraction+techniques+in+pollution+prevention+and+control.">Sustainability of solvent extraction techniques in pollution prevention and control.</a> Handbook of advanced approaches towards pollution prevention and control. , 33-66 (2021).</li><li>P&#322;otka-Wasylka, J., Rutkowska, M., Owczarek, K., Tobiszewski, M., Namie&#347;nik, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+with+environmentally+friendly+solvents.">Extraction with environmentally friendly solvents.</a> TrAC, Trends Anal Chem. 91, 12-25 (2017).</li><li>Queffelec, J., Beraud, W., Torres, M. D., Dom&#237;nguez, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+obtaining+ready-to-use+extracts+with+natural+solvents.">Advances in obtaining ready-to-use extracts with natural solvents.</a> Sustain Chem Pharm. 38, 101478 (2024).</li><li>Can Karaca, A., Erdem, I. G., Ak, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+polyols+on+gelation+kinetics,+gel+hardness,+and+drying+properties+of+alginates+subjected+to+internal+gelation.">Effects of polyols on gelation kinetics, gel hardness, and drying properties of alginates subjected to internal gelation.</a> LWT. 92, 297-303 (2018).</li><li>Nastasi, J. R., Daygon, V. D., Kontogiorgos, V., Fitzgerald, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Qualitative+analysis+of+polyphenols+in+glycerol+plant+extracts+using+untargeted+metabolomics.">Qualitative analysis of polyphenols in glycerol plant extracts using untargeted metabolomics.</a> Metabolites. 13 (4), 566 (2023).</li><li>Khat-Udomkiri, N., Gatnawa, G., Boonlerd, N., Myo, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Valorization+of+Camellia+sinensis+flowers+in+cosmetic+and+pharmaceutical+applications:+Optimization+of+microwave-assisted+glycerin+extraction.">Valorization of Camellia sinensis flowers in cosmetic and pharmaceutical applications: Optimization of microwave-assisted glycerin extraction.</a> Waste Biomass Valori. 15, 323-335 (2023).</li><li>Myo, H., Yaowiwat, N., Pongkorpsakol, P., Aonbangkhen, C., Khat-Udomkiri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Butylene+glycol+used+as+a+sustainable+solvent+for+extracting+bioactive+compounds+from+Camellia+sinensis+flowers+with+ultrasound-assisted+extraction.">Butylene glycol used as a sustainable solvent for extracting bioactive compounds from Camellia sinensis flowers with ultrasound-assisted extraction.</a> ACS omega. 8 (5), 4976-4987 (2023).</li><li>Myo, H., Khat-Udomkiri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+ultrasound-assisted+extraction+of+bioactive+compounds+from+coffee+pulp+using+propylene+glycol+as+a+solvent+and+their+antioxidant+activities.">Optimization of ultrasound-assisted extraction of bioactive compounds from coffee pulp using propylene glycol as a solvent and their antioxidant activities.</a> Ultrason Sonochem. 89, 106127 (2022).</li><li>Twaij, B. M., Hasan, M. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioactive+secondary+metabolites+from+plant+sources:+Types,+synthesis,+and+their+therapeutic+uses.">Bioactive secondary metabolites from plant sources: Types, synthesis, and their therapeutic uses.</a> Int J Plant Biol. 13 (1), 4-14 (2022).</li><li>Bitwell, C., Sen, I. S., Luke, C., Kakoma, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+modern+and+conventional+extraction+techniques+and+their+applications+for+extracting+phytochemicals+from+plants.">A review of modern and conventional extraction techniques and their applications for extracting phytochemicals from plants.</a> Sci Afr. 19, e01585 (2023).</li><li>Chakrabortty, S., Kumar, A., Patruni, K., Singh, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Recent advances in food biotechnology. , 353-370 (2022).</li><li>Fan, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanochemical+assisted+extraction+as+a+green+approach+in+preparation+of+bioactive+components+extraction+from+natural+products+-+A+review.">Mechanochemical assisted extraction as a green approach in preparation of bioactive components extraction from natural products - A review.</a> Trends Food Sci Technol. 129, 98-110 (2022).</li><li>Bessada, S. M., C Alves, R., Pp Oliveira, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coffee+silverskin:+A+review+on+potential+cosmetic+applications.">Coffee silverskin: A review on potential cosmetic applications.</a> Cosmetics. 5 (1), 5 (2018).</li><li>Myo, H., Nantarat, N., Khat-Udomkiri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+bioactive+compounds+of+coffee+pulp+through+fermentation-based+biotransformation+using+Lactobacillus+plantarum+TISTR+543+and+its+antioxidant+activities.">Changes in bioactive compounds of coffee pulp through fermentation-based biotransformation using Lactobacillus plantarum TISTR 543 and its antioxidant activities.</a> Fermentation. 7 (4), 292 (2021).</li><li>Molole, G. J., Gure, A., Abdissa, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+total+phenolic+content+and+antioxidant+activity+of+Commiphora+mollis+(oliv).+Engl.+Resin.">Determination of total phenolic content and antioxidant activity of Commiphora mollis (oliv). Engl. Resin.</a> BMC Chem. 16 (1), 48 (2022).</li><li>Barku, V., Opoku-Boahen, Y., Owusu-Ansah, E., Mensah, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antioxidant+activity+and+the+estimation+of+total+phenolic+and+flavonoid+contents+of+the+root+extract+of+Amaranthus+spinosus.">Antioxidant activity and the estimation of total phenolic and flavonoid contents of the root extract of Amaranthus spinosus.</a> Asian J Plant Sci Res. 3 (1), 69-74 (2013).</li><li>Samarasiri, M., Chandrasiri, T., Wijesinghe, D., Gunawardena, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antioxidant+capacity+and+total+phenolic+content+variations+against+Morinda+citrifolia+L.+fruit+juice+production+methods.">Antioxidant capacity and total phenolic content variations against Morinda citrifolia L. fruit juice production methods.</a> Int J Food Eng. 5, 293-299 (2019).</li><li>Rumpf, J., Burger, R., Schulze, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+evaluation+of+DPPH,+ABTS,+FRAP,+and+Folin-Ciocalteu+assays+to+assess+the+antioxidant+capacity+of+lignins.">Statistical evaluation of DPPH, ABTS, FRAP, and Folin-Ciocalteu assays to assess the antioxidant capacity of lignins.</a> Int J Biol Macromol. 233, 123470 (2023).</li><li>Lainez-Cer&#243;n, E., Ram&#237;rez-Corona, N., Jim&#233;nez-Mungu&#237;a, M. T., Palou, E., L&#243;pez-Malo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+bioactive+compounds+from+plants+by+means+of+new+environmentally+friendly+solvents.">Extraction of bioactive compounds from plants by means of new environmentally friendly solvents.</a> Research and technological advances in food science. , 301-332 (2022).</li><li>Yu, M., Gouvinhas, I., Rocha, J., Barros, A. I. R. N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phytochemical+and+antioxidant+analysis+of+medicinal+and+food+plants+towards+bioactive+food+and+pharmaceutical+resources.">Phytochemical and antioxidant analysis of medicinal and food plants towards bioactive food and pharmaceutical resources.</a> Sci Rep. 11 (1), 10041 (2021).</li><li>Lefebvre, T., Destandau, E., Lesellier, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+extraction+of+bioactive+compounds+from+plants+using+recent+extraction+techniques:+A+review.">Selective extraction of bioactive compounds from plants using recent extraction techniques: A review.</a> J Chromatogr A. 1635, 461770 (2021).</li><li>Nandasiri, R., Eskin, N. M., Thiyam-H&#246;llander, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antioxidative+polyphenols+of+canola+meal+extracted+by+high+pressure:+Impact+of+temperature+and+solvents.">Antioxidative polyphenols of canola meal extracted by high pressure: Impact of temperature and solvents.</a> J Food Sci. 84 (11), 3117-3128 (2019).</li><li>Jha, A. K., Sit, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+bioactive+compounds+from+plant+materials+using+combination+of+various+novel+methods:+A+review.">Extraction of bioactive compounds from plant materials using combination of various novel methods: A review.</a> Trends Food Sci Technol. 119, 579-591 (2022).</li><li>Czarnecki, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solvent+effect+on+the+competition+between+weak+and+strong+interactions+in+phenol+solutions+studied+by+near-infrared+spectroscopy+and+DFT+calculations.">Solvent effect on the competition between weak and strong interactions in phenol solutions studied by near-infrared spectroscopy and DFT calculations.</a> Phys Chem Chem Phys. 23 (35), 19188-19194 (2021).</li><li>Lu, W., Mackie, C. J., Xu, B., Head-Gordon, M., Ahmed, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+computational+and+experimental+view+of+hydrogen+bonding+in+glycerol+water+clusters.">A computational and experimental view of hydrogen bonding in glycerol water clusters.</a> J Phys Chem A. 126 (10), 1701-1710 (2022).</li><li>Fan, C., Liu, Y., Sebbah, T., Cao, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+theoretical+study+on+terpene-based+natural+deep+eutectic+solvent:+Relationship+between+viscosity+and+hydrogen-bonding+interactions.">A theoretical study on terpene-based natural deep eutectic solvent: Relationship between viscosity and hydrogen-bonding interactions.</a> Glob Chall. 5 (3), 2000103 (2021).</li><li>Liese, S., Schlaich, A., Netz, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectric+constant+of+aqueous+solutions+of+proteins+and+organic+polymers+from+molecular+dynamics+simulations.">Dielectric constant of aqueous solutions of proteins and organic polymers from molecular dynamics simulations.</a> J Chem Phys. 156 (22), 224903 (2022).</li><li>Noreland, E., Gestblom, B., Sj&#246;blom, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectric+relaxation+studies+of+1-hexanol+and+1,+2-hexanediol+in+heptane.">Dielectric relaxation studies of 1-hexanol and 1, 2-hexanediol in heptane.</a> J Solution Chem. 18, 303-312 (1989).</li><li>Wohlfarth, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Permittivity+(dielectric+constant)+of+liquids.">Permittivity (dielectric constant) of liquids.</a> CRC Handbook of Chemistry and Physics. 6, (1994).</li><li>Dean, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Extraction techniques for environmental analysis. , (2022).</li><li>Nour, A. H., Oluwaseun, A. R., Nour, A. H., Omer, M. S., Ahmed, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microwave-assisted+extraction+of+bioactive+compounds.">Microwave-assisted extraction of bioactive compounds.</a> Microwave heating. Electromagnetic fields causing thermal and non-thermal effects. , 1-31 (2021).</li><li>David, F., Ochiai, N., Sandra, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stir+bar+sorptive+extraction:+A+versatile,+sensitive+and+robust+technique+for+targeted+and+untargeted+analyses.">Stir bar sorptive extraction: A versatile, sensitive and robust technique for targeted and untargeted analyses.</a> Evolution of solid-phase microextraction technology. , (2023).</li><li>L&#243;pez-Fern&#225;ndez, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+polyphenols+using+liquid+chromatography-tandem+mass+spectrometry+technique+(LC-MS/MS):+A+review.">Determination of polyphenols using liquid chromatography-tandem mass spectrometry technique (LC-MS/MS): A review.</a> Antioxidants. 9 (6), 479 (2020).</li></ol>

The authors have nothing to disclose.

Various factors play a crucial role in the successful implementation of MAE, such as the phytochemical content of plant components, extraction duration, temperature, microwave power, solid-liquid ratio, and solvent concentration13. Plants typically exhibit varying profiles of phytochemicals; hence, the selection of natural plants rich in antioxidants and phenolic compounds is essential23. Furthermore, distinct bioactive constituents display a variety of polarities depending...

Nowadays, there is a global trend towards environmental awareness in the beauty industry, leading manufacturers to focus on green technology for extracting plant components using sustainable alternatives1. Typically, traditional solvents such as ethanol, methanol, and hexane are used to extract plant phenolic components and natural antioxidants2. Nevertheless, the presence of solvent residues within plant extracts poses a potential risk to human health, inducing skin and eye irritation3, particularly concerning their intended application in cosmetics. Consequently, it is challenging to eliminate such solvent residues from the extracts, a process that demands considerable investment in time, energy, and human resources4. Recently, superheated water, ionic liquids, deep eutectic solvents, and bio-derived solvents have emerged as promising approaches for green solvent extraction5. However, their use is still limited by product separation in aqueous-based processes. To address these challenges, the development of ready-to-use extracts emerges as a viable solution6.
Polyols are often used in cosmetic formulations as humectants because of their good polarity and ability to retain moisture from the environment7. In addition, polyols such as glycerin, propylene glycol, butylene glycol, methylpropanediol, isopentyldiol, pentylene glycol, 1,2-hexanediol, and hexylene glycol can be utilized for plant extractions. They are considered non-toxic, biodegradable, environmentally friendly, non-reactive, and safe solvents for use in plant extraction8. Additionally, polyols can withstand the heat generated during microwave-assisted extraction (MAE) due to their elevated boiling points and polarity9. These polyols are generally recognized as safe (GRAS) chemicals by the United States Food and Drug Administration (FDA). Unlike conventional solvents such as ethanol or methanol, which may require rigorous removal from the extract due to their potentially harmful effects, polyols offer the advantage of minimizing the energy, time, and costs associated with solvent removal processes10. This not only streamlines the extraction process but also enhances the overall efficiency and sustainability of the extraction method. Previous investigations have employed polyols such as propylene glycol and butylene glycol as solvents in the extraction of bioactive compounds from Camellia sinensis flowers10 and coffee pulp11, revealing significant potential for their role as sustainable alternative solvents in the plant extraction process. Thus, the continued development and optimization of a polyols-water solvent system holds the potential for significant advancements in green chemistry and sustainable industrial practices.
Generally, bioactive compounds found in plants are synthesized as secondary metabolites. These compounds can be categorized into three primary groups: terpenes and terpenoids, alkaloids, and phenolic compounds12. Various extraction methods are utilized under different conditions to isolate specific bioactive compounds from plants. Bioactive compounds from plant materials can be extracted using either conventional or non-conventional techniques. Traditional methods include maceration, reflux extraction, and hydro-distillation, while non-conventional methods consist of ultrasound-assisted extraction, enzyme-assisted extraction, microwave-assisted extraction (MAE), pulsed electric field-assisted extraction, supercritical fluid extraction, and pressurized liquid extraction13. These non-conventional methods are designed to enhance safety by utilizing safer solvents and auxiliaries, improving energy efficiency, preventing degradation of the bioactive components, and reducing environmental pollution14.
Furthermore, MAE is among the sophisticated green technologies for extracting bioactive compounds from plants. Conventional extraction procedures require significant amounts of time, energy, and high temperatures, which over time might degrade heat-sensitive bioactive compounds13. In contrast to conventional thermal extractions, MAE facilitates the extraction of bioactive compounds by generating localized heating within the sample, disrupting cell structures, and enhancing mass transfer, thereby increasing the efficiency of compound extraction. Heat is transferred from inside the plant cells by microwaves, which operate on the water molecules within the plant components13. Moreover, MAE has advanced to improve the extraction and separation of active compounds, increasing product yield, enhancing extraction efficiency, requiring fewer chemicals, and saving time and energy while preventing the destruction of bioactive compounds15.
This research focuses on the extraction of plant phenolic compounds and natural antioxidants through microwave-assisted extraction (MAE) using different types of polyols as solvents. The total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities (DPPH, ABTS, and FRAP) of polyol-based MAE extracts are determined. Additionally, polyol-based MAE is compared with MAE using conventional solvents such as water and ethanol. This research is expected to contribute to the development of environmentally sustainable extraction technology for natural components, promoting sustainability by reducing reliance on hazardous chemicals, shortening processing times, and minimizing energy consumption in raw material production for potential applications within the cosmetics industry.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1,2-Hexanediol</td>
			<td>Chanjao Longevity Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2,2 -Azino-bis 3 ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS)</td>
			<td>Sigma</td>
			<td>A1888</td>
			<td></td>
		</tr>
		<tr>
			<td>2,2-Diphenyl-1-picrylhydrazyl (DPPH)</td>
			<td>Sigma</td>
			<td>D9132</td>
			<td></td>
		</tr>
		<tr>
			<td>2,4,6-Tri(2-pyridyl)-s-triazine (TPTZ)</td>
			<td>Sigma</td>
			<td>93285</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Digital balance</td>
			<td>Ohaus</td>
			<td></td>
			<td>Pioneer</td>
		</tr>
		<tr>
			<td>4-Digital balance</td>
			<td>Denver</td>
			<td>SI-234</td>
			<td></td>
		</tr>
		<tr>
			<td>6-hydroxy-2,5,7,8 tetramethylchroman -2-carboxylic acid (Trolox)</td>
			<td>Sigma</td>
			<td>238813</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well plate</td>
			<td>SPL Life Science</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Absolute ethanol</td>
			<td>RCI Labscan</td>
			<td>64175</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>RCI Labscan</td>
			<td>64197</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum chloride</td>
			<td>Loba Chemie</td>
			<td>898</td>
			<td></td>
		</tr>
		<tr>
			<td>Automatic pipette</td>
			<td>Labnet</td>
			<td></td>
			<td>Biopett</td>
		</tr>
		<tr>
			<td>Butylene glycol</td>
			<td>Chanjao Longevity Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethos X advanced microwave extraction</td>
			<td>Milestone Srl, Sorisole, Italy</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ferrous sulfate</td>
			<td>Ajex Finechem</td>
			<td>3850</td>
			<td></td>
		</tr>
		<tr>
			<td>Folin-Ciocalteu&#39;s reagent</td>
			<td>Loba Chemie</td>
			<td>3870</td>
			<td></td>
		</tr>
		<tr>
			<td>Freezer SF</td>
			<td>Sanyo</td>
			<td>C697(GYN)</td>
			<td></td>
		</tr>
		<tr>
			<td>Gallic acid</td>
			<td>Sigma</td>
			<td>398225</td>
			<td></td>
		</tr>
		<tr>
			<td>Grinder</td>
			<td>Ou Hardware Products Co.,Ltd</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hexylene glycol</td>
			<td>Chanjao Longevity Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid (37%)</td>
			<td>RCI Labscan</td>
			<td>AR1107</td>
			<td></td>
		</tr>
		<tr>
			<td>Iron (III) chloride</td>
			<td>Loba Chemie</td>
			<td>3820</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopentyldiol</td>
			<td>Chanjao Longevity Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>RCI Labscan</td>
			<td>67561</td>
			<td></td>
		</tr>
		<tr>
			<td>Methylpropanediol&#160;</td>
			<td>Chanjao Longevity Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pentylene glycol</td>
			<td>Chanjao Longevity Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium persulfate</td>
			<td>Loba Chemie</td>
			<td>5420</td>
			<td></td>
		</tr>
		<tr>
			<td>Propylene glycol</td>
			<td>Chanjao Longevity Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Quercetin</td>
			<td>Sigma</td>
			<td>Q4951</td>
			<td></td>
		</tr>
		<tr>
			<td>Refrigerated centrifuge</td>
			<td>Hettich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium acetate</td>
			<td>Loba Chemie</td>
			<td>5758</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium carbonate</td>
			<td>Loba Chemie</td>
			<td>5810</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>RCI Labscan</td>
			<td>AR1325</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium nitrite</td>
			<td>Loba Chemie</td>
			<td>5954</td>
			<td></td>
		</tr>
		<tr>
			<td>SPECTROstar Nano microplate reader</td>
			<td>BMG- LABTECH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SPSS software</td>
			<td>IBM SPSS Statistics 20</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tray dryer</td>
			<td>France Etuves</td>
			<td>XUE343</td>
			<td></td>
		</tr>
	</tbody>
</table>

microwave-assisted extraction of phenolic compounds and antioxidants for cosmetic applications using polyol-based technology

The utilization of polyols as green solvents for extracting bioactive compounds from plant materials has gained attention due to their safety and inert behavior with plant bioactive chemicals. This study explores the sustainable extraction of phenolic compounds and natural antioxidants from coffee silverskin using the microwave-assisted extraction (MAE) method with polyol-based solvents: glycerin, propylene glycol (PG), butylene glycol (BG), methylpropanediol (MPD), isopentyldiol (IPD), pentylene glycol, 1,2-hexanediol, and hexylene glycol (HG). A comparative analysis was conducted on conventional and non-conventional solvent extractions, focusing on their impact on the bioactive compounds of MAE, encompassing parameters such as total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities like the 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay (DPPH), the 2,2&#8242;-azino-bis(-3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging assay (ABTS), and the ferric reducing antioxidant power assay (FRAP). The highest values were observed for TPC with aqueous-1,2-hexanediol extraction (52.0 &#177; 3.0 mg GAE/g sample), TFC with aqueous-1,2-hexanediol extraction (20.0 &#177; 1.7 mg QE/g sample), DPPH with aqueous-HG&#160;extraction (13.6 &#177; 0.3 mg TE/g sample), ABTS with aqueous-pentylene glycol extraction (8.2 &#177; 0.1 mg TE/g sample), and FRAP with aqueous-HG extraction (21.1 &#177; 1.3 mg Fe (II) E/g sample). This research aims to advance eco-friendly extraction technology through natural plant components, promoting sustainability by minimizing hazardous chemical use while reducing time and energy consumption, with potential applications in cosmetics.

Effect of polyols solvents and conventional solvents on total phenolic content, total flavonoid content, DPPH, FRAP, and ABTS antioxidant assays 
Solvent polarity should be compatible with that of targeted active molecules to improve the extraction efficiency of bioactive substances from plants22. Experiments were conducted using various solvents (water, ethanol, glycerin, propylene glycol, butylene glycol, methylpropanediol, isopentyldiol, pentylene glycol, 1,2-hexanediol, a...

Author Spotlight: Eco-Friendly Extraction of Bioactive Compounds Using Polyol-Based Microwave-Assisted Techniques

This protocol details the utilization of a polyol-based microwave-assisted extraction method for extracting phenolic compounds and natural antioxidants, representing a practical and environmentally sustainable approach to the development of ready-to-use extracts.

Microwave-Assisted Extraction of Phenolic Compounds and Antioxidants for Cosmetic Applications Using Polyol-Based Technology

The utilization of polyols as green solvents for extracting bioactive compounds from plant materials has gained attention due to their safety and inert ...

microwave-assisted-extraction-phenolic-compounds-antioxidants-for

Research

JoVE Journal

Chemistry

1.2K Views.  Mae Fah Laung University. This protocol details the utilization of a polyol-based microwave-assisted extraction method for extracting phenolic compounds and natural antioxidants, representing a practical and environmentally sustainable approach to the development of ready-to-use extracts.

Video: Author Spotlight: Eco-Friendly Extraction of Bioactive Compounds Using Polyol-Based Microwave-Assisted Techniques

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable.
The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts.
The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Microwave-assisted intramolecular dehydrogenative Diels-Alder (DA) reactions provide concise access to functionalized cyclopenta[b]naphthalene building blocks. The utility of this methodology is demonstrated by one-step conversion of the dehydrogenative DA cycloadducts into novel solvatochromic fluorescent dyes via Buchwald-Hartwig palladium-catalyzed cross-coupling reactions.

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to ...

Microwave-assisted Functionalization of Poly(ethylene glycol) and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large variety of PEG molecular weights and configurations (arm number, arm length, and branching pattern) affords researchers tight control over resulting hydrogel structures and properties, including Young&#8217;s modulus and mesh size. This video will illustrate a rapid, efficient, solvent-free, microwave-assisted method to methacrylate PEG precursors into poly(ethylene glycol) dimethacrylate (PEGDM). This synthetic method provides much-needed starting materials for applications in drug delivery and regenerative medicine. The demonstrated method is superior to traditional methacrylation methods as it is significantly faster and simpler, as well as more economical and environmentally friendly, using smaller amounts of reagents and solvents. We will also demonstrate an adaptation of this technique for on-resin methacrylamide functionalization of peptides. This on-resin method allows the N-terminus of peptides to be functionalized with methacrylamide groups prior to deprotection and cleavage from resin. This allows for selective addition of methacrylamide groups to the N-termini of the peptides while amino acids with reactive side groups (e.g.&#160;primary amine of lysine, primary alcohol of serine, secondary alcohols of threonine, and phenol of tyrosine) remain protected, preventing functionalization at multiple sites. This article will detail common analytical methods (proton Nuclear Magnetic Resonance spectroscopy (;H-NMR) and Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI-ToF)) to assess the efficiency of the functionalizations. Common pitfalls and suggested troubleshooting methods will be addressed, as will modifications of the technique which can be used to further tune macromer functionality and resulting hydrogel physical and chemical properties. Use of synthesized products for the formation of hydrogels for drug delivery and cell-material interaction studies will be demonstrated, with particular attention paid to modifying hydrogel composition to affect mesh size, controlling hydrogel stiffness and drug release.

Microwave-assisted Functionalization of Polyethylene glycol and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

This video will illustrate a rapid, efficient method to methacrylate poly(ethylene glycol), enabling chain polymerizations and hydrogel synthesis. It will demonstrate how to similarly introduce methacrylamide functionalities into peptides, detail common analytical methods to assess functionalization efficiency, provide suggestions for troubleshooting and advanced modifications, and demonstrate typical hydrogel characterization techniques.

One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large ...

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m2/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials.

Herein the procedures for plasma enhanced chemical vapor deposition of perfluoroalkanes on microporous materials such as metal-organic frameworks to enhance their stability and hydrophobicity are described. Furthermore, breakthrough testing of milligram quantities of samples is described in detail.

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes

The shift to heavy crude oils and the use of alternative fossil resources such as shale oil are a challenge for the petrochemical industry. The composition of heavy crude oils and shale oils varies substantially depending on the origin of the mixture. In particular they contain an increased amount of nitrogen containing compounds compared to the conventionally used sweet crude oils. As nitrogen compounds have an influence on the operation of thermal processes occurring in coker units and steam crackers, and as some species are considered as environmentally hazardous, a detailed analysis of the reactions involving nitrogen containing compounds under pyrolysis conditions provides valuable information. Therefore a novel method has been developed and validated with a feedstock containing a high nitrogen content, i.e., a shale oil. First, the feed was characterized offline by comprehensive two-dimensional gas chromatography (GC &#215; GC) coupled with a nitrogen chemiluminescence detector (NCD). In a second step the on-line analysis method was developed and tested on a steam cracking pilot plant by feeding pyridine dissolved in heptane. The former being a representative compound for one of the most abundant classes of compounds present in shale oil. The composition of the reactor effluent was determined via an in-house developed automated sampling system followed by immediate injection of the sample on a GC &#215; GC coupled with a time-of-flight mass spectrometer (TOF-MS), flame ionization detector (FID) and NCD. A novel method for quantitative analysis of nitrogen containing compounds using NCD and 2-chloropyridine as an internal standard has been developed and demonstrated.

A method combining comprehensive two-dimensional gas chromatography with nitrogen chemiluminescence detection has been developed and applied to on-line analysis of nitrogen containing compounds in a complex hydrocarbon matrix.

The shift to heavy crude oils and the use of alternative fossil resources such as shale oil are a challenge for the petrochemical industry. The ...

Simple Methods for the Preparation of Non-noble Metal Bulk-electrodes for Electrocatalytic Applications

The rock material pentlandite with the composition Fe4.5Ni4.5S8 was synthesized via high temperature synthesis from the elements. The structure and composition of the material was characterized via powder X-ray diffraction (PXRD), M&#246;ssbauer spectroscopy (MB), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and energy dispersive X-ray spectroscopy (EDX). Two preparation methods of pentlandite bulk electrodes are presented. In the first approach a piece of synthetic pentlandite rock is directly contacted via a wire ferrule. The second approach utilizes pentlandite pellets, pressed from finely ground powder, which is immobilized in a Teflon casing. Both electrodes, whilst being prepared by an additive-free method, reveal high durability during electrocatalytic conversions in comparison to common drop-coating methods. We herein showcase the striking performance of such electrodes to accomplish the hydrogen evolution reaction (HER) and present a standardized method to evaluate the electrocatalytic performance by electrochemical and gas chromatographic methods. Furthermore, we report stability tests via potentiostatic methods at an overpotential of 0.6 V to explore the material limitations of the electrodes during electrolysis under industrial relevant conditions.

A facile preparation method of electrodes using the bulk material Fe4.5Ni4.5S8 is presented. This method provides an alternative technique to conventional electrode fabrication and describes prerequisites for unconventional electrode materials including a straightforward electrocatalytic testing method.

The rock material pentlandite with the composition Fe4.5Ni4.5S8 was synthesized via high temperature synthesis from the elements. The structure and ...

Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical properties, which allow for the absorption of near-infrared (NIR) light and can subsequently convert it into multiplexed emissions that span over a broad range of regions from the UV to the visible to the NIR. This article presents detailed experimental procedures for high-temperature co-precipitation synthesis of core-shell UCNs that incorporate different lanthanide ions into nanocrystals for efficiently converting deep-tissue penetrable NIR excitation (808 nm) into a strong blue emission at 480 nm. By controlling the surface modification with biocompatible polymer (polyacrylic acid, PAA), the as-prepared UCNs acquires great solubility in buffer solutions. The hydrophilic nanocrystals are further functionalized with specific ligands (dibenzyl cyclooctyne, DBCO) for localization on the cell membrane. Upon NIR light (808 nm) irradiation, the upconverted blue emission can effectively activate the light-gated channel protein on the cell membrane and specifically regulate the cation (e.g., Ca2+) influx in the cytoplasm. This protocol provides a feasible methodology for the synthesis of core-shell lanthanide-doped UCNs and subsequent biocompatible surface modification for further cellular applications.

A protocol is presented for the synthesis of core-shell lanthanide-doped upconversion nanocrystals (UCNs) and their cellular applications for channel protein regulation upon near-infrared (NIR) light illumination.

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical ...

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

The goal of the following procedure is to provide a demonstration of the one-pot conversion of a 2-azido-1-nitrate-ester to a trichloroacetimidate glycosyl donor. Following azido-nitration of a glycal, the product 2-azido-1-nitrate ester can be hydrolyzed under microwave-assisted irradiation. This transformation is usually achieved using strongly nucleophilic reagents and extended reaction times. Microwave irradiation induces hydrolysis, in the absence of reagents, with short reaction times. Following denitration, the intermediate anomeric alcohol is converted, in the same pot, to the corresponding 2-azido-1-trichloroacetimidate.

A 2-azido-1-nitrate-ester can be converted to the corresponding 2-azido-1-trichloroacetimidate in a one-pot procedure. The goal of the manuscript is to demonstrate utility of the microwave reactor in carbohydrate synthesis.

The goal of the following procedure is to provide a demonstration of the one-pot conversion of a 2-azido-1-nitrate-ester to a trichloroacetimidate ...

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance (EPR) or ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopies, we obtain useful information such as electron affinity, ionization potential, band-gap energies, the type of charge carriers, and degradation information that can be used to synthesize stable organic electronic devices. In this study, we present electrochemical and spectroelectrochemical methods to analyze the processes occurring in active layers of an organic device as well as the generated charge carriers.

In this article, we describe electrochemical, electron paramagnetic resonance, and ultraviolet-visible and near-infrared spectroelectrochemical methods to analyze organic compounds for application in organic electronics.

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance ...

Escherichia coli-Based Cell-Free Protein Synthesis: Protocols for a robust, flexible, and accessible platform technology

Over the last 50 years, Cell-Free Protein Synthesis (CFPS) has emerged as a powerful technology to harness the transcriptional and translational capacity of cells within a test tube. By obviating the need to maintain the viability of the cell, and by eliminating the cellular barrier, CFPS has been foundational to emerging applications in biomanufacturing of traditionally challenging proteins, as well as applications in rapid prototyping for metabolic engineering, and functional genomics. Our methods for implementing an E. coli-based CFPS platform allow new users to access many of these applications. Here, we describe methods to prepare extract through the use of enriched media, baffled flasks, and a reproducible method of tunable sonication-based cell lysis. This extract can then be used for protein expression capable of producing 900 &#181;g/mL or more of super folder green fluorescent protein (sfGFP) in just 5 h from experimental setup to data analysis, given that appropriate reagent stocks have been prepared beforehand. The estimated startup cost of obtaining reagents is $4,500 which will sustain thousands of reactions at an estimated cost of $0.021 per &#181;g of protein produced or $0.019 per &#181;L of reaction. Additionally, the protein expression methods mirror the ease of the reaction setup seen in commercially available systems due to optimization of reagent pre-mixes, at a fraction of the cost. In order to enable the user to leverage the flexible nature of the CFPS platform for broad applications, we have identified a variety of aspects of the platform that can be tuned and optimized depending on the resources available and the protein expression outcomes desired.

Escherichia coli-Based Cell-Free Protein Synthesis: Protocols for a robust, flexible, and accessible platform technology

This protocol details the steps, costs, and equipment necessary to generate E. coli-based cell extracts and implement in vitro protein synthesis reactions within 4 days or less. To leverage the flexible nature of this platform for broad applications, we discuss reaction conditions that can be adapted and optimized.

Over the last 50 years, Cell-Free Protein Synthesis (CFPS) has emerged as a powerful technology to harness the transcriptional and translational capacity ...