Monoamine oxidase inhibition by southern African traditional medicinal plants

Traditional health care is utilized by a large majority of the population in southern Africa. This is particularly true of treatment for mental health problems. A large part of the treatment regimes used by traditional healers involve numerous herbal preparations. Twenty plants used traditionally were screened for MAO inhibition and specific MAO-B inhibition activity. MAO-B inhibitors are currently employed in the treatment of neurodegenerative related illnesses such as Parkinson's and Alzheimer's disease. A photometric peroxidase linked assay was used to determine the inhibition of the oxidative deamination of tyramine by MAO isolated from rat liver. Ruta graveolens exhibited the best MAO inhibitory activity (ethyl acetate leaf extract = IC50 5 ± 1 μg/ml, petroleum ether extract = 3 ± 1 μg/ml) and specific MAO-B inhibition (ethyl acetate leaf extract = IC50 7 ± 6 μg/ml petroleum ether extract = 3 ± 1 μg/ml). Schotia brachypetala, Mentha aquatica and Gasteria croucheri also exhibited good MAO-B inhibition activity. These findings support these plants traditional use and may lead to the discovery of novel MAO inhibitors.