Antimicrobial activity of some Hypericum species.

The crude methanolic extracts of six species of Hypericum [H. caprifoliatum Cham. & Schlecht., H. carinatum Griseb., H. connatum Lam., H. ternum A. St. Hil., H. myrianthum Cham. & Schlecht. and H. polyanthemum Klotzsch ex Reichardt] growing in southern Brazil were analyzed for antimicrobial activity against several microorganisms (bacteria and fungi). The most active plant was H. caprifoliatum, which showed activity against Staphylococcus aureus. Only H. polyanthemum and H. ternum extracts were active against Bacillus subtilis. None of the crude methanolic extracts showed activity against S. epidermidis, Escherichia coli or Saccharomyces cerevisiae. Extracts from these species were evaluated chemically and tannin, flavonoid and phenolic acids were the prominent compounds. The plants contained quercitrin, hyperoside (except H. connatum) and, less frequently, isoquercitrin and chlorogenic acid. In contrast to H. perforatum, which has high concentrations of rutin, these species do not produce this flavonoid or it appears as traces. The tannin concentration varied between 5.1 and 16.7% in H. myrianthum and H. ternum, respectively.