Abstract
One new flavonoid named (2R,3R)-7-O-galloylplumbocatechin A (1) and three known flavonoids, (−)-5,3',4',5'-tetrahydroxyflavan-7-gallate (2), (+)-3,5,3',4',5'-penta-hydroxyflavan-7-gallate (3), and (−)-7,4'-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.
Highlights
The influenza virus is a highly infective agent that causes acute pulmonary diseases [1,2,3]
The leaves and twigs of P. clypearia were collected from Shankou, Beihai City, Guangxi Province in May 2012 and were identified by Professor Lin Ma, Department of Natural Products Chemistry, Institute of Materia Medica (IMM), Chinese Academy of Medical Sciences and Peking Union Medical
Confluent monolayers of A549 cells in 96-well plates at 37 °C in 5% CO2 infected with influenza virus (H1N1) at MOI 0.1 were treated with flavonoids at the serially diluted, non-cytotoxic concentrations of 3, 10 and 30 μg/mL
Summary
The influenza virus is a highly infective agent that causes acute pulmonary diseases [1,2,3]. Recent studies have shown that certain strains of influenza virus, such as H5N1, are more likely to induce excessive cytokine release and immune cell exudation [6,7]. P. clypearia has been found to contain various flavonoids It has been used as a herbal medicine in the treatment of respiratory tract diseases in China for many years [9,10,11,12]. The chemical constituents of the EtOAc extract were separated, and their NA inhibitory and anti-inflammatory activities were both evaluated to partially reveal the responsible compounds and the mechanism of action against influenza virus
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