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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

The present protocol describes the contamination of pyrrolizidine alkaloids (PAs) in tea samples from PA-producing weeds in tea gardens.

Abstract

Toxic pyrrolizidine alkaloids (PAs) are found in tea samples, which pose a threat to human health. However, the source and route of PA contamination in tea samples have remained unclear. In this work, an adsorbent method combined with UPLC-MS/MS was developed to determine 15 PAs in the weed Ageratum conyzoides L., A. conyzoides rhizospheric soil, fresh tea leaves, and dried tea samples. The average recoveries ranged from 78%-111%, with relative standard deviations of 0.33%-14.8%. Fifteen pairs of A. conyzoides and A. conyzoides rhizospheric soil samples and 60 fresh tea leaf samples were collected from the Jinzhai tea garden in Anhui Province, China, and analyzed for the 15 PAs. Not all 15 PAs were detected in fresh tea leaves, except for intermedine-N-oxide (ImNO) and senecionine (Sn). The content of ImNO (34.7 µg/kg) was greater than that of Sn (9.69 µg/kg). In addition, both ImNO and Sn were concentrated in the young leaves of the tea plant, while their content was lower in the old leaves. The results indicated that the PAs in tea were transferred through the path of PA-producing weeds-soil-fresh tea leaves in tea gardens.

Introduction

As secondary metabolites, pyrrolizidine alkaloids (PAs) protect plants against herbivores, insects, and pathogens1,2. Up to now, over 660 PAs and PA-N-oxides (PANOs) with different structures have been found in more than 6,000 plant species worldwide3,4. PA-producing plants are mainly found in the families Asteraceae, Boraginaceae, Fabaceae, and Apocynaceae5,6. PAs are easily oxidized to unstable dehydropyrrolizidine alkaloids, which have strong electrophilic....

Protocol

For the present study, the following weed species were collected: Ludwigia prostrata Roxb., Murdannia triquetra (Wall. ex C. B. Clarke) Bruckn., Ageratum conyzoides L., Chenopodium ambrosioides, Trachelospermum jasminoide (L.) Lem., Ageratum conyzoides L., Emilia sonchifolia (L.) DC, Ageratum conyzoides L., and Crassocephalum crepidioides (Benth.) S. Moore. The fresh tea leaves were picked from the variety of Longjing 43# tea tree.......

Representative Results

The optimized adsorbent purification and analysis method of 15 PAs in dried tea samples, fresh tea leaves, weeds, and soil was established and compared with the commonly used purification method using the SPE cartridge. The results showed that the recoveries of the 15 PAs in dried tea samples, weed, and fresh tea leaves using the SPE cartridge were 72%-120%, while that using adsorbent purification was 78%-98% (Figure 1). The recoveries of the 15 PAs in soil using adsorbent purification were .......

Discussion

The present work was designed to develop an effective, sensitive method to explore the contamination routes and sources of PAs in tea samples as well as the distribution of PAs in different parts of the tea plants. However, in this study, only 15 PAs were successfully separated on the chromatographic column, which is a very small number in comparison to the large number of alkaloids in plant species3,4. This was not only related to the packing properties of the c.......

Acknowledgements

This work was supported by the National Natural Scientific Foundation of China (32102244), the National Agricultural Products Quality and Safety and Risk Assessment Project (GJFP2021001), the Natural Scientific Foundation of Anhui Province (19252002), and the USDA (HAW05020H).

....

Materials

NameCompanyCatalog NumberComments
Acetonitrile (99.9%)Tedia Company,Inc.21115197CAS No:75-05-8
Ammonia (25%-28%)Wuxi Zhanwang Chemical Reagent Co., Ltd.181210CAS No:1336-21-6
Ammonium formate (97.0%)Anpel Laboratory Technoiogies (shanghai)G0860050CAS No:540-69-2
Carbon-GCBCNWB7760030120-400 MESH, 10g. per box 
Centrifuge Z 36 HKHERMLEZ36HK30000 rpm (min:10 rpm), Dimensions (W x H x D): 71.5 cm× 42 cm × 51 cm
Commercially available tea productLvming, Qingshan, Luyuchun, Changling, Huixing, Wuyunjian, Heshengchunloose teaGreen tea
Europine N-oxid (EuNO) (98.0%)BioCrick323256CAS No:65582-53-8
Europine (Eu) (98.0%)BioCrick98222CAS No:570-19-4
Formate (98.0%)AladdinE2022005CAS No:64-18-6
HC-C18CNWD211006040-63 μm,100g.per box
Heliotrine (He) (98.0%)BioCrick906426CAS No:303-33-3
Heliotrine-N-oxide (HeNO) (98.0%)BioCrick22581CAS No:6209-65-0
High speed centrifuge TG16-WScence203158000Max:16000 r/min, 330 × 390 × 300 mm (L × W × H), Capacity: 6 × 50 mL
HSS T3 columnWaters186004976ACQUITY UPLC HSS T3 (2.1 × 100 mm 1.8 μm)
Intermedine (Im) (98.0%)BioCrick114843CAS No:10285-06-0
Intermedine-N-oxide (ImNO) (98.0%)BioCrick340066CAS No:95462-14-9
Jacobine (Jb) (98.0%)BioCrick132282048CAS No:6870-67-3
Jacobine-N-oxide (JbNO) (98.0%)ChemFacesCFN00461CAS No:38710-25-7
Methyl Alcohol (99.9%)Tedia Company,Inc.21115100CAS No:67-56-1
PSAAgelaP19-0083340-60 μm, 60 Å 100g.per box
Retrorsine (Re) (98.0%)BioCrick5281743CAS No:480-54-6
Retrorsine-N-oxide (ReNO) (98.0%)BioCrick5281734CAS No:15503-86-3
Senecionine (Sc) (98.0%)BioCrick5280906CAS No:130-01-8
Senecionine-N-oxide (ScNO) (98.0%)BioCrick5380876CAS No:13268-67-2
Seneciphylline N-oxid (SpNO) (98.0%)BioCrick6442619CAS No:38710-26-8
Seneciphylline (Sp) (98.0%)BioCrick5281750CAS No:480-81-9
Senkirkine (Sk) (98.0%)BioCrick5281752CAS No:2318-18-5
SPE PCXAgilent Technologies12108206Cation Mixed Mode, 6 mL
Sulfuric acid (97%)Wuxi Zhanwang Chemical Reagent Co., Ltd.1003019CAS No:7664-93-9
Trisodium citrateSinpharm Chemical Reagent Co., Ltd.20121009CAS No:6132-04-3
Ultrasonic cleanerSupmileKQ-600BInner slot size: 500 × 300 × 150 mm; Capacity: 22.5 L
UPLC-xevoTQMSWatersZPLYY-003Triple four-stage rod mass analyzer, Waters Alliance 2695/Waters ACQUITY UPLC Liquid Phase System
Water bath thermostat oscillatorGuoyu instrumentSHY-2AHSOscillation times:  60-300 times/min, Constant temperature range: room temperature to 100 °C

References

  1. Schramm, S., Kohler, N., Rozhon, W. Pyrrolizidine alkaloids: Biosynthesis, biological activities and occurrence in crop plants. Molecules. 24 (3), 498 (2019).
  2. EFSA Panel on Contaminants in the Food Chain (CONTAM).

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