Abstract:
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 ED50 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.
