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

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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.

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

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

This research talks about finding eco-friendly ways to extract plant bioactive compounds. We are testing how well microwave assisted extraction with the polyol-based solvents work for extracting plants bioactive substances, especially phenol compounds. Additionally, exploring this method could lead to more efficient and effective extraction technique for the cosmetic industries.Today's cosmetic research is also about using green technology and green chemistry. Nonconventional extraction techniques such as microwave-assist extraction, and extraction, have been interestingly employed to extract plants bioactive compounds. However, organic solvents are still commonly utilized for bioactive component extraction.Using polyol-based solvent for microwave assistant extraction turned out to be more effective than using traditional solvent like water and ethanol. The results show that the plant extract obtained with polyol have higher level of phenolic content for the flavanoid content and antioxidant activity. Compared to those extracted with conventional solvent.Our procedure stands out because it is beneficial, environmentally friendly and safe for human health. It is also more energy efficient and cost effective than traditional processes, making it an excellent alternative for sustainable and simple production. Our finding show that polyols combined with unconventional extraction methods can extract phenol compounds.The next challenge is whether this extraction method can be used to extract other plant, secondary metabolized, and if it can be commercialized to extract bioactive compounds for cosmetic purposes.

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...

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.

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

Extraction of Phenolic Compounds and Natural Antioxidants from Coffee Silverskin Using the Polyol-Based Microwave-Assisted Extraction Method

To begin, place the diluted 60%solvents for microwave assisted extraction on the working platform. Weigh 0.67 grams of the coffee silver skin and mix with 20 milliliters of extraction solvent at a one is to 30 ratio in a reaction container. Add a magnetic stir bar to the vessel to ensure uniform distribution of the heat and solvent within the sample.Close the vessel firmly with a special tool and place it into the microwave assisted extraction chamber. To set up the method, click on the toolbox icon on the top bar of the monitor and select the SK eT rotor in the accessory section. Then click on the stir and type 20%to set the stirring rate.Click on the door lock sector and set it to activate at temperatures exceeding 80 degrees Celsius. Then click on the table icon on the top bar and set the temperature gradient T1 to an extraction duration of 10 minutes. Microwave power to 1800 watts and temperature to 120 degrees Celsius.To activate the stir, click on the stir button and wait until the green light appears. Set the blower fan speed to level three. To hold the extraction time, select the desired extraction temperature T2 by setting the extraction duration to 15 minutes, the microwave power to 1800 watts and the temperature to 120 degrees Celsius.Now, click on the cooling button at the lower left corner of the screen and select the cooling time of 10 minutes. Click the Save icon at the top right corner of the screen. Start the extraction process by choosing the number of vessels used.Following extraction, centrifuge extracts at 9072g for 15 minutes at four degrees Celsius. Collect the supernatant with a 10 milliliter glass pipette and store it at minus 20 degrees Celsius. Dilute the coffee silver skin extracts tenfold with distilled water in a 96 well plate.Mix 10 microliters of the diluted sample with 20 microliters of undiluted folin-ciocalteu reagent, and allow them to react for three minutes. Next, add 100 microliters of 7.5%sodium carbonate solution to the mixture in each well of a 96 well plate. Prepare different concentrations for the gallic acid standard concentration range by diluting with distilled water.Mix them with 20 microliters of folin-ciocalteu reagent, and allow them to react for three minutes. Next, add 100 microliters of 7.5%sodium carbonate solution to the mixture in each well of a 96 well plate. Incubate the reaction for 30 minutes in the dark at room temperature.On a microplate reader, measure the absorbance of the reaction mixture at 765 nanometers. Plot the standard calibration curve using the concentrations of the standard and absorbance at 765 nanometers. Express the results as milligrams of gallic acid equivalent per gram of the sample.Aqueous 1, 2 hexanediol extraction yielded the highest total phenolic content and water extraction yielded the lowest. Aqueous 1, 2 hexanediol extraction yielded the highest total flavonoid content and aqueous isopentyldiol extraction yielded the lowest. Aqueous hexylene glycol extraction exhibited the highest DPPH assay value and aqueous ethanol extraction exhibited the lowest.Aqueous pentylene glycol extraction resulted in the highest ABTS assay value and water extraction resulted in the lowest. Aqueous hexylene glycol extraction showed the highest FRAP value and water extraction showed the lowest.

628 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.

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

Summary