Abstract

E. O. Iwalewa*, V. Naidoo, V. Bagla and J. N. Eloff

Preliminary pharmacological screening of the aqueous extract from the leaves, stem and root of Harungana madagascariensis Lam. ex Poiret (Guttiferae) are reported to have effect on some cardiovascular diseases like bleeding, cadiopathy, hematuria, and other complications. However, the mechanism underlying its therapeutic effect is not known. The effects of six extracts from the stem bark of H. madagascariensis on equine platelets and chicken hepatocyte cells were explored to examine the involvement of nitric oxide (NO) in platelet aggregation and cell viability capacity. Extracts exhibited concentration dependent platelet aggregation, and synergistically increased NO synthesis in platelets pre-treated with NO and prostaglandin (PG) inhibitors (L-NAME and ASA). The ED50 values observed in the extracts of H. madagascariensis extracts in this study were potentiated and the graphs were shifted to the left in the presence of both inhibitors. However, a contrary effect was observed in berberine, in which its ED 50 was shifted to the right non-competitively by the inhibitors. These results demonstrate that extracts from the stem of H. madagascariensis stimulates NO release and this may be a mechanism whereby the constituents of the plant elicit its therapeutic effects in herbal medicine. This study may have relevance in hemostasis, thrombosis and cancer chemotherapy.