α‑Glucosidase Inhibitory Activities and the Interaction Mechanism of Novel Spiro-Flavoalkaloids from YingDe Green Tea

Flavoalkaloids are a unique class of compounds in tea, most of which have an N-ethyl-2-pyrrolidinone moiety substituted at the A ring of a catechin skeleton. 1-Ethyl-5-hydroxy-pyrrolidone, a decomposed product of theanine, was supposed to be the key intermediate to form tea flavoalkaloids. However,...

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Published in:Journal of agricultural and food chemistry 2022-01, Vol.70 (1), p.136-148
Main Authors: Hou, Zhi-Wei, Chen, Chen-Hui, Ke, Jia-Ping, Zhang, Yuan-Yuan, Qi, Yan, Liu, Shi-Yu, Yang, Zi, Ning, Jing-Ming, Bao, Guan-Hu
Format: Article
Language:English
Subjects:
Alkaloids - pharmacology
alpha-Glucosidases
Bioactive Constituents, Metabolites, and Functions
Camellia sinensis - chemistry
Catechin
Glycoside Hydrolase Inhibitors - pharmacology
Tea - chemistry
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Summary:Flavoalkaloids are a unique class of compounds in tea, most of which have an N-ethyl-2-pyrrolidinone moiety substituted at the A ring of a catechin skeleton. 1-Ethyl-5-hydroxy-pyrrolidone, a decomposed product of theanine, was supposed to be the key intermediate to form tea flavoalkaloids. However, we have also detected another possible theanine intermediate, 1-ethyl-5-oxopyrrolidine-2-carboxylic acid, and speculated if there are related conjugated catechins. Herein, four novel spiro-flavoalkaloids with a spiro-γ-lactone structural moiety were isolated from Yingde green tea (Camellia sinensis var. assamica) in our continuing exploration of new chemical constituents from tea. The structures of the new compounds, spiro-flavoalkaloids A-D (1–4), were further elucidated by extensive nuclear magnetic resonance (NMR) spectroscopy together with the calculated 13C NMR, IR, UV–vis, high-resolution mass, optical rotation, experimental, and calculated circular dichroism spectra. We also provided an alternative pathway to produce these novel spiro-flavoalkaloids. Additionally, their α-glucosidase inhibitory activities were determined with IC50 values of 3.34 (1), 5.47 (2), 22.50 (3), and 15.38 (4) μM. Docking results revealed that compounds 1 and 2 mainly interacted with residues ASP-215, ARG-442, ASP-352, GLU-411, HIS-280, ARG-315, and ASN-415 of α-glucosidase through hydrogen bonds. The fluorescence intensity of α-glucosidase could be quenched by compounds 1 and 2 in a static style.
ISSN:0021-8561
1520-5118
DOI:10.1021/acs.jafc.1c06106