Inhibition of Naja naja venom enzymes by the methanolic extract of Leucas aspera and its chemical profile by GC–MS

PURPOSE: The present investigation was aimed at evaluating the anti-ophidian properties of ethnomedicinal herb Leucas aspera against Indian cobra, Naja naja venom enzymes. METHODS: Methanolic extract of Leucas aspera was evaluated, in vitro, for its ability to inhibit the major enzyme activities of Naja naja venom including protease, phospholipase A(2), hyaluronidase and hemolytic factors. The type of phytochemicals present in the extract was analyzed. Also, the major phytoconstituents in the extract was determined by gas chromatography–mass spectrometry (GC–MS). RESULTS: Venom protease and hyaluronidase activities (two isoforms) were completely (100%) neutralized by the L. aspera methanolic extract at ratio of 1:50 w/w (venom: plant extract) and venom hemolytic activity was also completely neutralized at a ratio of 1:80 w/w by the plant extract. However, the extract failed to neutralize phospholipase A(2) activity even at the highest concentration used. Phytochemical analysis revealed the presence of alkaloids, acidic compounds, flavonoids, steroids and cardiac glycosides in the extract. GC–MS analysis indicated that a total of 14 compounds were present in the extract. The major bioactive constituents were found to be 6-octadecenoic acid (32.47%), n-hexadecanoic acid (25.97%), and 17-octadecen-14-yn-1-ol (14.22%) along with the minor constituents, sitosterol (2.45%) and stigmasterol (2%), which was previously reported to exhibit antivenom activity. CONCLUSION: The results obtained demonstrate for the first time that the methanolic extract of Leucas aspera possesses anti-venom activity and could be considered as a potential source for the anti-ophidian metabolites.