1
|
Wang H, Zhu B, Qiao S, Dong C, Wan X, Gong W, Zhang Z. Structure and evolution of alanine/serine decarboxylases and the engineering of theanine production. eLife 2024; 12:RP91046. [PMID: 39287621 PMCID: PMC11407765 DOI: 10.7554/elife.91046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2024] Open
Abstract
Ethylamine (EA), the precursor of theanine biosynthesis, is synthesized from alanine decarboxylation by alanine decarboxylase (AlaDC) in tea plants. AlaDC evolves from serine decarboxylase (SerDC) through neofunctionalization and has lower catalytic activity. However, lacking structure information hinders the understanding of the evolution of substrate specificity and catalytic activity. In this study, we solved the X-ray crystal structures of AlaDC from Camellia sinensis (CsAlaDC) and SerDC from Arabidopsis thaliana (AtSerDC). Tyr341 of AtSerDC or the corresponding Tyr336 of CsAlaDC is essential for their enzymatic activity. Tyr111 of AtSerDC and the corresponding Phe106 of CsAlaDC determine their substrate specificity. Both CsAlaDC and AtSerDC have a distinctive zinc finger and have not been identified in any other Group II PLP-dependent amino acid decarboxylases. Based on the structural comparisons, we conducted a mutation screen of CsAlaDC. The results indicated that the mutation of L110F or P114A in the CsAlaDC dimerization interface significantly improved the catalytic activity by 110% and 59%, respectively. Combining a double mutant of CsAlaDCL110F/P114A with theanine synthetase increased theanine production 672% in an in vitro system. This study provides the structural basis for the substrate selectivity and catalytic activity of CsAlaDC and AtSerDC and provides a route to more efficient biosynthesis of theanine.
Collapse
Affiliation(s)
- Hao Wang
- Department of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Biying Zhu
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, China
| | - Siming Qiao
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, China
| | - Chunxia Dong
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, China
| | - Xiaochun Wan
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, China
| | - Weimin Gong
- Department of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Zhaoliang Zhang
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, China
| |
Collapse
|
2
|
Zang E, Jiang L, Cui H, Li X, Yan Y, Liu Q, Chen Z, Li M. Only Plant-based Food Additives: An Overview on Application, Safety, and Key Challenges in the Food Industry. FOOD REVIEWS INTERNATIONAL 2022. [DOI: 10.1080/87559129.2022.2062764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- Erhuan Zang
- Department of Pharmacy, Baotou Medical College, Baotou, Inner Mongolia, China
| | - Linlin Jiang
- Department of Pharmacy, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China
| | - Hongwei Cui
- Clinical research center, The Affiliated Hospital of Inner Mongolia Medical University/Key Laboratory of Medical Cell Biology of Inner Mongolia Autonomous Region, Hohhot, Inner Mongolia, China
| | - Xing Li
- Department of Pharmacy, Baotou Medical College, Baotou, Inner Mongolia, China
| | - Yumei Yan
- Department of Pharmacy, Baotou Medical College, Baotou, Inner Mongolia, China
| | - Qian Liu
- Department of Pharmacy, Baotou Medical College, Baotou, Inner Mongolia, China
| | - Ziwei Chen
- Department of Pharmacy, Baotou Medical College, Baotou, Inner Mongolia, China
| | - Minhui Li
- Department of Pharmacy, Baotou Medical College, Baotou, Inner Mongolia, China
- Department of Pharmacy, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China
- Pharmaceutical Laboratory, Inner Mongolia Hospital of Traditional Chinese Medicine, Hohhot, Inner Mongolia, China
- Inner Mongolia Institute of Traditional Chinese and Mongolian Medicine, Hohhot, Inner Mongolia, China
- Inner Mongolia Key Laboratory of Characteristic Geoherbs Resources Protection and Utilization, Baotou Medical College, Baotou, Inner Mongolia, China
| |
Collapse
|
3
|
Evans M, McDonald AC, Xiong L, Crowley DC, Guthrie N. A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave ® L-Theanine on Stress in a Healthy Adult Population. Neurol Ther 2021; 10:1061-1078. [PMID: 34562208 PMCID: PMC8475422 DOI: 10.1007/s40120-021-00284-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 09/09/2021] [Indexed: 11/13/2022] Open
Abstract
Introduction Stress is a complex life occurrence essential for survival and goal achievement but can be damaging in excess. Because of the high prevalence of stress in North America, a safe supplement that effectively reduces stress is in demand. The objective of this study was to investigate the efficacy and safety of AlphaWave®l-Theanine on whole-scalp and frontal alpha power, midline theta power, and salivary cortisol in healthy, moderately stressed adults. Methods This was a randomized, triple-blind, placebo-controlled, crossover study that consisted of two study periods with a 7-day washout. A single dose of AlphaWave®l-Theanine (200 mg) or placebo was administered. To induce stress, a mental arithmetic test (MAT) was administered before and after the dose. Electroencephalogram, salivary cortisol, blood pressure, heart rate, self-reported stress, adverse events, clinical chemistry, and hematology were assessed to evaluate efficacy and safety. Results Increases in heart rate, blood pressure, and self-reported stress and state anxiety indicated that participants experienced stress during the MAT. AlphaWave®l-Theanine led to a greater increase in frontal region and whole-scalp alpha power 3 h post-dose compared to placebo (p ≤ 0.050). Within groups, there were increases in alpha power, at 3 h with AlphaWave®l-Theanine, over the whole recording and during the eyes-open portions (p ≤ 0.048) of the alpha task. The changes in alpha wave activity are supported by greater decreases in salivary cortisol 1 h post-dose (p < 0.001) with AlphaWave®l-Theanine compared to placebo. Conclusion This study was conducted during the SARS-CoV-2 pandemic, which has had a rapid and significant effect on both physical and mental health around the world. A single dose of AlphaWave®l-Theanine significantly increased frontal region alpha power compared to placebo in response to an acute stress challenge. These changes are indicative of relaxation in the brain and suggest a calming response. AlphaWave®l-Theanine was found to be safe and well tolerated by participants. Trial Registration ClinicalTrials.gov identifier NCT04706494. Stress is a complex part of life that is essential for survival and achieving goals. Too much stress, however, can be damaging. There is a high prevalence of stress in North America, creating a demand for a safe and effective supplement to reduce it. This study investigated the effectiveness and safety of AlphaWave®l-Theanine on brainwaves and salivary cortisol in healthy, moderately stressed adults facing an acute stressor. This was a randomized, triple-blind, placebo-controlled, crossover study that consisted of two study periods with a 7-day washout. A single dose of 200 mg of AlphaWave®l-Theanine or placebo was administered before and after a mental arithmetic test to elicit acute stress. Electroencephalogram, salivary cortisol, blood pressure, heart rate, self-reported stress, and safety were assessed to evaluate efficacy and safety. This study was conducted during the coronavirus pandemic, which has had a rapid and significant effect on both physical and mental health around the world. A single dose of AlphaWave®l-Theanine had significant positive effects on brainwaves, salivary cortisol, and self-reported state anxiety compared to the placebo in response to an acute stress challenge. These changes are indicative of relaxation in the brain and suggest a calming response in a moderately stressed but otherwise healthy population. AlphaWave®l-Theanine was found to be safe and well tolerated by participants.
Collapse
Affiliation(s)
- Malkanthi Evans
- KGK Science Inc., 255 Queens Ave, London, ON, N6A 5R8, Canada.
| | | | - Lora Xiong
- Ethical Naturals, Inc., 2731 Fair Oaks Ave, Redwood City, CA, 94063, USA
| | - David C Crowley
- KGK Science Inc., 255 Queens Ave, London, ON, N6A 5R8, Canada
| | - Najla Guthrie
- KGK Science Inc., 255 Queens Ave, London, ON, N6A 5R8, Canada
| |
Collapse
|
4
|
Wang Y, Chen F, Ma Y, Zhang T, Sun P, Lan M, Li F, Fang W. An ancient whole-genome duplication event and its contribution to flavor compounds in the tea plant (Camellia sinensis). HORTICULTURE RESEARCH 2021; 8:176. [PMID: 34333548 PMCID: PMC8325681 DOI: 10.1038/s41438-021-00613-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 05/12/2021] [Accepted: 05/20/2021] [Indexed: 05/14/2023]
Abstract
Tea, coffee, and cocoa are the three most popular nonalcoholic beverages in the world and have extremely high economic and cultural value. The genomes of four tea plant varieties have recently been sequenced, but there is some debate regarding the characterization of a whole-genome duplication (WGD) event in tea plants. Whether the WGD in the tea plant is shared with other plants in order Ericales and how it contributed to tea plant evolution remained unanswered. Here we re-analyzed the tea plant genome and provided evidence that tea experienced only WGD event after the core-eudicot whole-genome triplication (WGT) event. This WGD was shared by the Polemonioids-Primuloids-Core Ericales (PPC) sections, encompassing at least 17 families in the order Ericales. In addition, our study identified eight pairs of duplicated genes in the catechins biosynthesis pathway, four pairs of duplicated genes in the theanine biosynthesis pathway, and one pair of genes in the caffeine biosynthesis pathway, which were expanded and retained following this WGD. Nearly all these gene pairs were expressed in tea plants, implying the contribution of the WGD. This study shows that in addition to the role of the recent tandem gene duplication in the accumulation of tea flavor-related genes, the WGD may have been another main factor driving the evolution of tea flavor.
Collapse
Affiliation(s)
- Ya Wang
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Fei Chen
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
| | - Yuanchun Ma
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Taikui Zhang
- College of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Pengchuan Sun
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Meifang Lan
- College of Life Sciences, North China University of Science and Technology, Tangshan, 063099, China
| | - Fang Li
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Wanping Fang
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
| |
Collapse
|
5
|
Jin W, Zhang Z, Zhu K, Xue Y, Xie F, Mao S. Comprehensive Understanding of the Bacterial Populations and Metabolites Profile of Fermented Feed by 16S rRNA Gene Sequencing and Liquid Chromatography-Mass Spectrometry. Metabolites 2019; 9:metabo9100239. [PMID: 31640120 PMCID: PMC6835224 DOI: 10.3390/metabo9100239] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/14/2019] [Accepted: 10/15/2019] [Indexed: 02/01/2023] Open
Abstract
The comprehensive bacterial populations and metabolites profile in fermented feed is unclear, which may have significant effects on the stability of fermented feed quality and animal gut health. In this study, 16S rRNA gene sequencing and liquid chromatography–mass spectrometry were used to explore the bacterial populations and metabolites profile in the fermented feed incubated with probiotics (MF) or without probiotics (SF). The probiotics were a combination of Lactobacillus salivarius, Bacillus subtilis, and Saccharomyces cerevisiae. The pH and lactic acid levels were higher in MF than in SF (P < 0.05), while the total volatile fatty acid content was lower (P < 0.05). Interestingly, after fermentation, the most abundant bacterial genus in MF was Enterococcus, rather than the added probiotics Lactobacillus or Bacillus. Weissella and a few potential pathogens (Enterobacter, Escherichia-Shigella, and Pantoea) were dominant in SF (P < 0.05). Metabolomics analysis identified 32 different metabolites in the two types of fermented feed. These metabolites enriched in MF, such as maleic acid, phenylacetic acid, ethyl linoleate, dihomo-gamma-linolenic acid, and L-theanine had potential antimicrobial activities. Conclusively, the addition of probiotics enriched a few potentially beneficial microbes and small molecular compounds with antimicrobial activities, and inhibited the potential pathogens in fermented feed.
Collapse
Affiliation(s)
- Wei Jin
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
- National Center for International Research on Animal Gut Nutrition, Nanjing Agricultural University, Nanjing 210095, China.
- National Experimental Teaching Demonstration Center of Animal Science, Nanjing Agricultural University, Nanjing 210095, China.
| | - Zheng Zhang
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
| | - Kun Zhu
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
| | - Yanfeng Xue
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
| | - Fei Xie
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
| | - Shengyong Mao
- Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
- National Center for International Research on Animal Gut Nutrition, Nanjing Agricultural University, Nanjing 210095, China.
- National Experimental Teaching Demonstration Center of Animal Science, Nanjing Agricultural University, Nanjing 210095, China.
| |
Collapse
|
6
|
Saeed M, Naveed M, Arif M, Kakar MU, Manzoor R, Abd El-Hack ME, Alagawany M, Tiwari R, Khandia R, Munjal A, Karthik K, Dhama K, Iqbal HMN, Dadar M, Sun C. Green tea (Camellia sinensis) and l-theanine: Medicinal values and beneficial applications in humans-A comprehensive review. Biomed Pharmacother 2017; 95:1260-1275. [PMID: 28938517 DOI: 10.1016/j.biopha.2017.09.024] [Citation(s) in RCA: 134] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Revised: 09/03/2017] [Accepted: 09/06/2017] [Indexed: 02/05/2023] Open
Abstract
Green tea (Camellia sinensis) is a famous herb, and its extract has been extensively used in traditional Chinese medicinal system. In this context, several studies have revealed its health benefits and medicinal potentialities for several ailments. With ever increasing scientific knowledge, search for safer, potential and novel type of health-related supplements quest, scientists are re-directing their research interests to explore natural resources i.e. medicinal herbs/plant derived compounds. Green tea consumption has gained a special attention and popularity in the modern era of changing lifestyle. The present review is aimed to extend the current knowledge by highlighting the importance and beneficial applications of green tea in humans for safeguarding various health issues. Herein, we have extensively reviewed, analyzed, and compiled salient information on green tea from the authentic published literature available in PubMed and other scientific databases. Scientific literature evidenced that owing to the bioactive constituents including caffeine, l-theanine, polyphenols/flavonoids and other potent molecules, green tea has many pharmacological and physiological functions. It possesses multi-beneficial applications in treating various disorders of humans. This review also provides in-depth insights on the medicinal values of green tea which will be useful for researchers, medical professionals, veterinarians, nutritionists, pharmacists and pharmaceutical industry. Future research emphasis and promotional avenues are needed to explore its potential therapeutic applications for designing appropriate pharmaceuticals, complementary medicines, and effective drugs as well as popularize and propagate its multidimensional health benefits.
Collapse
Affiliation(s)
- Muhammad Saeed
- College of Animal Science and Technology, NW A&F University, Yangling, Shaanxi, 712100, China; Institute of Animal Sciences, Faculty of Animal Husbandry, University of Agriculture, Faisalabad, 38040, Pakistan
| | - Muhammad Naveed
- Department of Clinical Pharmacy, School of Basic Medicine, and Clinical Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu Province, 211198, China; Department of Urology Surgery, Aviation General Hospital, Beijing, 100012, China
| | - Muhammad Arif
- Department of Animal Sciences, University College of Agriculture, University of Sargodha, 40100, Pakistan
| | - Mohib Ullah Kakar
- Faculty of Marine Sciences, Lasbela University of Agriculture, Water and Marine Sciences, Uthal, Balochistan, 3800, Pakistan
| | - Robina Manzoor
- Faculty of Marine Sciences, Lasbela University of Agriculture, Water and Marine Sciences, Uthal, Balochistan, 3800, Pakistan
| | | | - Mahmoud Alagawany
- Poultry Department, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt.
| | - Ruchi Tiwari
- Department of Veterinary Microbiology and Immunology, College of Veterinary Sciences, UP Pandit Deen Dayal Upadhayay Pashu Chikitsa Vigyan Vishwavidyalay Evum Go-Anusandhan Sansthan (DUVASU), Mathura, Uttar Pradesh, 281 001, India
| | - Rekha Khandia
- Department of Biochemistry and Genetics, Barkatullah University, Bhopal, 462 026 M.P., India
| | - Ashok Munjal
- Department of Biochemistry and Genetics, Barkatullah University, Bhopal, 462 026 M.P., India
| | - Kumaragurubaran Karthik
- Central University Laboratory, Tamil Nadu Veterinary and Animal Sciences University, Madhavaram Milk Colony, Chennai, Tamil Nadu, 600051, India
| | - Kuldeep Dhama
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, 243 122, Uttar Pradesh, India
| | - Hafiz M N Iqbal
- Tecnologico de Monterrey, School of Engineering and Sciences, Campus Monterrey, Ave. Eugenio Garza Sada 2501, Monterrey, N.L., CP 64849, Mexico
| | - Maryam Dadar
- Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
| | - Chao Sun
- College of Animal Science and Technology, NW A&F University, Yangling, Shaanxi, 712100, China.
| |
Collapse
|
7
|
Türközü D, Şanlier N. L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety. Crit Rev Food Sci Nutr 2015; 57:1681-1687. [DOI: 10.1080/10408398.2015.1016141] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
8
|
Rogers PJ, Smith JE, Heatherley SV, Pleydell-Pearce CW. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology (Berl) 2008; 195:569-77. [PMID: 17891480 DOI: 10.1007/s00213-007-0938-1] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Accepted: 09/03/2007] [Indexed: 11/29/2022]
Abstract
RATIONALE Although both contain behaviourally significant concentrations of caffeine, tea is commonly perceived to be a less stimulating drink than coffee. At least part of the explanation for this may be that theanine, which is present in tea but not coffee, has relaxing effects. There is also some evidence that theanine affects cognitive performance, and it has been found to reduce blood pressure in hypertensive rats. OBJECTIVES To study the subjective, behavioural and blood pressure effects of theanine and caffeine administered alone and together, in doses relevant to the daily tea consumption of regular tea drinkers. MATERIALS AND METHODS In a randomised, double-blind, placebo-controlled study, healthy adult participants (n = 48) received either 250-mg caffeine, 200-mg theanine, both or neither of these. They completed ratings of mood, including anxiety, and alertness, and had their blood pressure measured before and starting 40 min after drug administration. Anxiety was also assessed using a visual probe task. RESULTS Caffeine increased self-rated alertness and jitteriness and blood pressure. Theanine antagonised the effect of caffeine on blood pressure but did not significantly affect jitteriness, alertness or other aspects of mood. Theanine also slowed overall reaction time on the visual probe task. CONCLUSIONS Theanine is a physiologically and behaviourally active compound and, while it is unclear how its effects might explain perceived differences between tea and coffee, evidence suggests that it may be useful for reducing raised blood pressure.
Collapse
Affiliation(s)
- Peter J Rogers
- Department of Experimental Psychology, University of Bristol, 12a Woodland Road, Bristol, BS8 1TU, UK.
| | | | | | | |
Collapse
|
9
|
Venzie JL, Castro J, Balarama Krishna MV, Nelson DM, Marcus RK. Electron-impact and glow-discharge ionization LC-MS analysis of green tea tincture. Anal Bioanal Chem 2006; 387:321-33. [PMID: 17139484 DOI: 10.1007/s00216-006-0934-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 10/02/2006] [Accepted: 10/12/2006] [Indexed: 10/23/2022]
Abstract
A liquid chromatography-particle-beam mass spectrometer (LC-PB/MS) with interchangeable electron-impact (EI) and glow-discharge (GD) ion sources was evaluated for future application in analysis of botanical extracts. In this work a green tea tincture was characterized for a series of catechin components (catechin, epicatechin, epigallocatechin, and epigallocatechin gallate (EGCG)) and caffeine. Special emphasis was given to EGCG and caffeine, because they are important in determining the possible health effects of the green tea. The effects of instrument operating conditions were evaluated for the EI and GD ionization sources to determine their effect on analyte intensities and fragmentation patterns. These studies furnished information about the effects of these conditions in determining possible ionization pathways in the two ion sources. The mass spectra of these compounds obtained with the GD ion source are EI-like in appearance, with clearly identified molecular ions and fragmentation patterns that are easily rationalized. The absolute limits of detection for EGCG and caffeine were, respectively, 11 ng and 0.77 ng for the EI source and 3.2 ng and 0.61 ng for the GD source. The PB/EIMS and PB/GDMS combinations can be operated in a flow-injection mode, wherein the analyte is injected directly into the mobile phase, or coupled to high-performance liquid chromatography (HPLC), enabling LC-MS analysis of complex mixtures. A reversed-phase chromatographic separation of the green tea tincture was performed on a commercial C18 column using a gradient of water (containing 0.1% TFA) and ACN. Quantification of EGCG and caffeine was performed by the standard addition method. The amounts of EGCG and caffeine in the tested green tea tincture were each approximately 14 mg mL-1.
Collapse
Affiliation(s)
- Jacob L Venzie
- Department of Chemistry, Clemson University, Biosystems Research Complex, 51 New Cherry St., Clemson, SC 29634-1905, USA
| | | | | | | | | |
Collapse
|