Monoamine oxidase inhibitory activity of some Hypericum species native to South Brazil.

The total methanol crude extracts and petroleum ether, chloroform, and methanol fractions obtained from Hypericum species, H. caprifoliatum, H. carinatum, H. connatum, H. cordatum, H. myrianthum, H. piriai, H. polyanthemum and H. brasiliense, all native to South Brazil, were assayed for monoamine oxidase A (MAO A) and MAO B inhibitory activity in rat brain mitochondrial preparations at concentrations ranging from 1 to 20 μg mL−1. Three benzo-pyrans, HP1 (6-isobutyryl-5,7-dimethoxy-2,2-dimethylbenzopyran), HP2 (7-hydroxy-6-iso-butyryl-5-methoxy-2,2-dimethylbenzopyran) and HP3 (5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethylbenzopyran) isolated from H. polyanthemum were also tested at maximal concentrations of 150, 150 and 75 μ, respectively. The lipophilic extracts of H. polyanthemum, H. caprifoliatum and H. piriai displayed MAO A inhibitory activity greater than 50%. Among the benzopyrans, only HP3 showed significant activity, with an IC50 value of 22 μ. The total methanol crude extracts of aerial parts from H. carinatum, H. connatum, H. cordatum, H. polyanthemum and H. piriai were evaluated for antidepressant activity in the Porsolt's forced swimming test in Wistar rats (270 mg kg−1 day−1; i.p); however, none of them showed activity.