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A-type proanthocyanidins from lychee seeds and their antioxidant and antiviral activities
Xinya Xu1, Haihui Xie, Yifei Wang
1Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, PR China.
Abstract:
Two new A-type trimeric proanthocyanidins with two doubly bonded interflavanoid linkages, litchitannin A1 [epicatechin-(2β→O→7,4β→6)-epicatechin-(2β→O→7,4β→8)-catechin] (1) and litchitannin A2 [epicatechin-(2β→O→7,4β→6)-epicatechin-(2β→O→7,4β→6)-epicatechin] (2), were isolated from lychee (Litchi chinensis Sonn. cv. Heiye) seeds together with aesculitannin A (3), epicatechin-(2β→O→7,4β→8)-epiafzelechin-(4α→8)-epicatechin (4), proanthocyanidin A1 (5), proanthocyanidin A2 (6), proanthocyanidin A6 (7), epicatechin-(7,8-bc)-4β-(4-hydroxyphenyl)-dihydro-2(3H)-pyranone (8), and epicatechin (9). Their structures were elucidated on the basis of spectroscopic and chemical evidence. It is the first time that compounds 1-4, 7, and 8 have been reported in this species. Compounds 1-9 showed more potent antioxidant activity than L-ascorbic acid with ferric reducing antioxidant power (FRAP) values of 3.71-24.18 mmol/g and IC50 values of 5.25-20.07 μM toward DPPH radicals. Moreover, litchitannin A2 (2) was found to exhibit in vitro antiviral activity against coxsackie virus B3 (CVB3) and compounds 3 and 6 displayed antiherpes simplex virus 1 (HSV-1) activity.
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