A study of the histaminic activity of extract of Mucuna pruriens

This study investigated the pharmacological activity of the principle from the spines of the seed pods of Mucuna pruriens using contraction of guinea pig ileum as index of pharmacological activity. The active principle was extracted with 0.0015 M NaCl. Muscle strips of guinea pig ileum were prepared and contractile responses were measured using a Kymograph. Two sets of experiments were conducted viz: the contraction of the ileum in the presence of different concentrations of histamine, 2 – methylhistamine and the extract of Mucuna pruriens and the contractile response of the ileum in the presence of different concentrations of the extract and antagonists – diphenhydramine, atropine and methysergide. Mucuna pruriens extract, 2 – methylhistamine and histamine produced dose dependent contraction of guinea pig ileum (Extract ED50 = 13.0 ig/ml; 2 – methylhistamine ED=50-8.5 ig/ml and Histamine ED50=10 ig/ml). Diphenhydramine, an H1 antagonist competitively blocked the contractile response of the extract and coadministration of the extract either with different doses of antimuscarinic agent atropine or 5 – hydroxytryptamine blocking agent, methysergide did not alter the extract - induced contractile response of the guinea pig ileum. These results demonstrate that the spines of Mucuna pruriens possess histamine activity which may contribute to its itching and painful irritation effects.