Evidence for existence of venom 5′ nucleotidase in multiple forms through inhibition of concanavalin A

Plant-Derived Toxin Inhibitors as Potential Candidates to Complement Antivenom Treatment in Snakebite Envenomations

Snakebite envenomations (SBEs) are a neglected medical condition of global importance that mainly affect the tropical and subtropical regions. Clinical manifestations include pain, edema, hemorrhage, tissue necrosis, and neurotoxic signs, and may evolve to functional loss of the affected limb, acute renal and/or respiratory failure, and even death. The standard treatment for snake envenomations is antivenom, which is produced from the hyperimmunization of animals with snake toxins. The inhibition of the effects of SBEs using natural or synthetic compounds has been suggested as a complementary treatment particularly before admission to hospital for antivenom treatment, since these alternative molecules are also able to inhibit toxins. Biodiversity-derived molecules, namely those extracted from medicinal plants, are promising sources of toxin inhibitors that can minimize the deleterious consequences of SBEs. In this review, we systematically synthesize the literature on plant metabolites that can be used as toxin-inhibiting agents, as well as present the potential mechanisms of action of molecules derived from natural sources. These findings aim to further our understanding of the potential of natural products and provide new lead compounds as auxiliary therapies for SBEs.

Mitochondriotropic action and DNA protection: Interactions between phenolic acids and enzymes

The protective action of caffeic (CA) and syringic (SA) acids on the genotoxicity exercised by snake venoms was investigated in this study. Molecular interactions between phenolic acids and the enzyme succinate dehydrogenase were also explored. In the electrophoresis assay, SA did not inhibit the genotoxicity induced by the venom. However, CA partially inhibited DNA degradation. In the comet assay, SA and CA exerted an inhibitory effect on the venom-induced fragmentation. Succinate dehydrogenase presented, in computational analyzes, favorable energies to the molecular bond to both the malonic acid and the phenolic compounds evaluated. In the enzymatic activity assays, SA inhibited succinate dehydrogenase and interfered in the interaction of malonic acid. Meanwhile, CA potentiated the inhibition exerted by the malonic acid. The results suggest transient interactions between toxins present in venoms and phenolic acids, mainly by hydrogen interactions, which corroborate with the data from previous works.

Vanillin analog--vanillyl mandelic acid, a novel specific inhibitor of snake venom 5'-nucleotidase

Snake venom 5'-nucleotidase (5'NUC) plays a very important role in envenomation strategies; however, apart from its modulation of hemostatic functions, its other pharmacological effects are not yet well characterized. Several studies have used specific inhibitors of enzyme toxins as a biochemical or pharmacological tool to characterize or establish its mechanism of action. We report here for the first time vanillin mandelic acid (VMA), an analog of vanillin, to potentially, selectively, and specifically inhibit venom 5'NUC activity among other enzymes present in venoms. VMA is much more potent in inhibiting 5'NUC activity than vanillyl acid (VA). The experimental results obtained are in good agreement with the in silico molecular docking interaction data. Both VA and VMA are competitive inhibitors as evident by the inhibition-relieving effect upon increasing the substrate concentration. VMA also dose-dependently inhibited the anticoagulant effect in Naja naja venom. In this study, we report novel non-nucleoside specific inhibitors of snake venom 5'NUC and experimentally demonstrate their involvement in the anticoagulant activity of N. naja venom. Hence, we hypothesize that VMA can be used as a molecular tool to evaluate the role of 5'NUC in snake envenomation and to develop prototypes and lead compounds with potential therapeutic applications against snake bites.