In vitro 5-lipoxygenase and anti-oxidant activities of South African medicinal plants commonly used topically for skin diseases.

An investigation was undertaken to determine the possible mechanisms of action of medicinal plants used for dermatological pathologies. A total of 14 plant species were selected from the readily available ethnobotanical literature. 5-Lipoxygenase and DPPH (2,2-diphenyl-1-picrylhydrazyl) assays were used to determine the anti-inflammatory activity and the anti-oxidant activity of selected medicinal plants, respectively. Both aqueous and methanol extracts were tested. Among the plants screened, four species (Croton sylvaticus, Warburgia salutaris, Pentanisia prunelloides, and Melianthus comosus) displayed promising 5-lipoxygenase inhibitory activity with IC(50) values <61 ppm. A large number of plants exhibited significant anti-oxidant activities with IC(50) values between 5.27 and 83.36 ppm. Aqueous extracts of M. comosus exhibited the most potent anti-inflammatory and anti-oxidant activity.