C‑8 N‑Ethyl-2-pyrrolidinone-Substituted Flavan-3-ols from the Leaves of Camellia sinensis var. pubilimba

Camellia sinensis var. pubilimba, one variety of the genus Camellia sect. Thea (Theaceae), has been used for producing green tea mainly by the local people of its growing areas of Guangxi province, China. Forty compounds, including eight C-8 N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (1–8) and...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2018-07, Vol.66 (27), p.7150-7155
Main Authors: Meng, Xiu-Hua, Zhu, Hong-Tao, Yan, Hui, Wang, Dong, Yang, Chong-Ren, Zhang, Ying-Jun
Format: Article
Language:English
Subjects:
Antioxidants - chemistry
Antioxidants - pharmacology
Camellia sinensis - chemistry
Cholinesterase Inhibitors - chemistry
Cholinesterase Inhibitors - pharmacology
Flavonoids - chemistry
Flavonoids - pharmacology
Inhibitory Concentration 50
Magnetic Resonance Spectroscopy
Molecular Structure
Plant Leaves - chemistry
Pyrrolidinones - chemistry
Pyrrolidinones - pharmacology
Tea - chemistry
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Summary:Camellia sinensis var. pubilimba, one variety of the genus Camellia sect. Thea (Theaceae), has been used for producing green tea mainly by the local people of its growing areas of Guangxi province, China. Forty compounds, including eight C-8 N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (1–8) and their substituted unit N-ethyl-5-hydroxy-2-pyrrolidinone (9), four flavan-3-ol monomers (10–13) and one dimer (14), nine flavonoids (15–23), three hydrolyzable tannins (24–26), two lignans (27–28), 11 simple phenolics (29–39), and caffeine (40), were first isolated and identified from the leaves. Their structures were determined by detailed spectroscopic analysis and comparison with the literature data and authentic samples. Both 1 and 4 were obtained as a mixture of the N-ethyl-2-pyrrolidinone C-5 enantiomers (1a and 1b and 4a and 4b), respectively, while the resolution of another three pairs of enantiomers (2 and 3, 5 and 6, and 7 and 8) was achieved. Among them, 1b is a new compound whose NMR data together with its enantiomer (1a) were reported for the first time, while 2 and 3 are two new natural products. Most of the isolates exhibited significant antioxidant activities, stronger than ascorbic acid and trolox, while parts of the isolates, particularly C-8 N-ethyl-2-pyrrolidinone-substituted flavan-3-ols, showed obvious inhibitory effects on acetylcholinesterase (AChE). The results indicated that C. sinensis var. pubilimba is a valuable plant resource for tea production.
ISSN:0021-8561
1520-5118
DOI:10.1021/acs.jafc.8b02066