Antimicrobial activity of seven hypericum entities from central Italy.

Methanol-acetone extracts from aerial parts of seven entities of the genus Hypericum [H. perforatum L. subsp. perforatum, H. perforatum L. subsp. veronense (Schrank) Ces., H. montanum L., H. hyssopifolium Chaix, H. hirsutum L., H. hircinum L. subsp. majus (Aiton) N. Robson, H. tetrapterum Fr.] growing in the Appennino Umbro-Marchigiano (central Italy) were tested in vitro for their antimicrobial activity against two Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis), two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and the yeast Candida albicans, by the Kirby-Bauer agar diffusion method. The two H. perforatum subspecies were particularly active against Gram-positive and Gram-negative bacteria, supporting the use of these plants in the traditional medicine of central Italy to treat wounds, skin and infectious diseases. However significant values of inhibition were given also by H. hirsutum against S. aureus and P. aeruginosa, and by H. hyssopifolium, H. hircinum subsp. majus and H. tetrapterum against C. albicans. These results suggest that hypericin and hyperforin are the main components responsible for antimicrobial activity, but not the only ones, as other extracts, showing a low level of these compounds, possess evident activity. Isolation of pure compounds from the most active extracts is in progress.