DOIAbstract
One new flavonoid named (2R,3R)-7-O-galloylplumbocatechin A (1) and three known flavonoids, (−)-5,3\u27,4\u27,5\u27-tetrahydroxyflavan-7-gallate (2), (+)-3,5,3\u27,4\u27,5\u27-penta-hydroxyflavan-7-gallate (3), and (−)-7,4\u27-di-O-galloyltricetiflavan (4), were isolated from Pithecellobium clypearia Benth. Their structures were elucidated based on spectroscopic analysis, including homonuclear and heteronuclear correlation NMR (HSQC and HMBC) experiments. In vitro assays, compounds 1 and 2 showed moderate inhibitory effects against influenza H1N1 virus neuraminidase (NA). Compounds 1–4 were all found to inhibit the expression of proinflammatory cytokines IL-6 or MCP-1 induced by influenza H1N1 virus in human A549 lung carcinoma cells
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