α-Glucosidase Inhibitory Activities and the Interaction Mechanism of Novel Spiro-Flavoalkaloids from YingDe Green Tea
α-Glucosidase Inhibitory Activities and the Interaction Mechanism of Novel Spiro-Flavoalkaloids from YingDe Green Tea
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DOI：
10.1021/acs.jafc.1c06106
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发表时间：
2021-12-29
影响因子：
6.1
通讯作者：
Bao, Guan-Hu
中科院分区：
文献类型：
--
作者：
Hou, Zhi-Wei;Chen, Chen-Hui;Bao, Guan-Hu
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-gamma-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 C-13 NMR, IR, UV-vis, highresolution mass, optical rotation, experimental, and calculated circular dichroism spectra. We also provided an alternative pathway to produce these novel spiro-flavoalkaloids. Additionally, their alpha-glucosidase inhibitory activities were determined with IC50 values of 3.34 (1), 5.47 (2), 22.50 (3), and 15.38 (4) mu M. 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 alpha-glucosidase through hydrogen bonds. The fluorescence intensity of alpha-glucosidase could be quenched by compounds 1 and 2 in a static style.
