Antimicrobial and antinematode activity of Hypericum androsaemum

Hypericum androsaemum L. (HA) grows wild in shadowy sites, namely in the northern region of Portugal, where it is widely used as a medicinal herb. This species is used in popular medicinal preparations as a cholagogue, hepatoprotector, and diuretic and in kidney failure [1]. The HA water extracts were assayed against the microorganisms Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Candida albicans, and the plant parasitic nematode Meloidogyne javanica. Either the minimum inhibitory concentration or the minimum lethal concentration were higher than 8 mg/mL when the infusion was tested against E. coli, C. albicans, and S. cerevisiae, showing their low sensibility to HA. However, when tested against B. subtilis, the minimum inhibitory concentration was lower than 0.5 mg/mL and the minimum lethal concentration was lower than 2.0 mg/mL. Cumulative eclosion of M. javanica juveniles of second stage (J2) was calculated by counting, every 24h, the juveniles ecloded from samples of 20 eggs exposed to 4, 6, 8, and 10 mg/mL of lyophilized extract. For mortality studies egg masses of M. javanica were placed on a small square piece of muslin with 30 µm diameter openings supported as a small sieve in a glass block (2 ml cap.); about 1 ml tap water was added, until the muslin was just submerged. Juveniles collected during the first 24h were discarded and the subsequent J2 collected were used. Twenty J2 were exposed to 2 ml of each concentration of the lyophilized extract: 4, 6, 8 and 10 mg/mL. A relation between the concentration of the extract and hatching of M. javanica was found. However, apparently there was no eclosion in the first 24h. The mortality of J2 of M. javanica was also directly dependent on the concentration of the extract being observed in the first 24 hours for 6, 8 and 10 mg/mL but only after 72h at the concentration of 4 mg/mL.