Inhibition of secretary PLA₂--VRV-PL-VIIIa of Russell's viper venom by standard aqueous stem bark extract of Mangifera indica L.

The aqueous extract of Mangifera indica is known to possess anti-snake venom activities. However, its inhibitory potency and mechanism of action on multi-toxic phospholipases A2s, which are the most toxic and lethal component of snake venom is still unknown. Therefore, this study was carried out to evaluate the modulatory effect of standard aqueous bark extract of M. indica on VRV-PL-VIIIa of Indian Russells viper venom. Mangifera indica extract dose dependently inhibited the GIIB sPLA2 (VRV-PL-VIIIa) activity with an IC50 value of 6.8±0.3 μg/ml. M. indica extract effectively inhibited the indirect hemolytic activity up to 96% at ~40 μg/ml concentration. Further, M. indica extract at different concentrations (0-50 μg/ml) inhibited the edema formed in a dose dependent manner. It was found that there was no relieve of inhibitory effect of the extract when examined as a function of increased substrate and calcium concentration. The inhibition was irreversible as evident from binding studies. The in vitro inhibition is well correlated with in situ and in vivo edema inducing activities. As the inhibition is independent of substrate, calcium concentration and was irreversible, it can be concluded that M. indica extracts mode of inhibition could be due to direct interaction of components present in the extract with PLA2 enzyme. In conclusion, the aqueous extract of M. indica effectively inhibits svPLA2 (Snake venom phospholipase A2) enzymatic and its associated toxic activities, which substantiate its anti-snake venom properties. Further in-depth studies are interesting to known on the role and mechanism of the principal inhibitory constituents present in the extract, so as to develop them into potent anti-snake venom and as an anti-inflammatory agent.