In vitro anti-HCV activities of Saxifraga melanocentra and its related polyphenolic compounds.

The aim of this study was to search for new natural anti-HCV agents from Chinese herbal medicine. Bioactivity-guided extraction and isolation methods were used. Active part and pure compounds were obtained from ethanolic extract of Saxifraga melanocentra Franch. and their in vitro inhibitory activities (IC50) against HCV NS3 serine protease were tested by enzyme-linked immunosorbent assay. Results showed that the polyphenolic ethyl acetate part of the herbal extract was the most active, and from this 18 polyphenols representing active compounds were isolated and identified. IC50 values of these compounds and five related ones were obtained. A broad-degree of anti-HCV activity was observed among them in the following order: gallated esters of D-glucose and rutin (0.68-4.86 microM)> flavonoids (33.11-370.37 microM)> gallic acid and its methyl and ethyl esters, Bergenin and others (over 1000 microM). The most active compound was 1,2,3,4,6-penta-O-galloyl-beta-D-glucoside (0.68 microM). In conclusion, polyphenols were responsible for the anti-HCV constitution of S. melanocentra, and multigallated esters of D-glucose possessed the strongest inhibition against HCV NS3 serine protease and little cytotoxic effect, suggesting the potential use of these compounds for designing and developing drugs for treatment of the viral infection.