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Several Brazilian plants have been utilized in folk medicine as active agents against various effects induced by snake venoms. The inhabitants of the Amazon region use, among others, the macerated bark of a plant popularly named "Pracaxi" (Pentaclethra macroloba Willd) to combat these effects. We report now the antihemorrhagic properties against snake venoms of the aqueous extract of Pentaclethra macroloba (EPema). EPema exhibited full inhibition of hemorrhagic and nucleolytic activities induced by several snake venoms. Additionally, partial inhibition of myotoxic, lethal, phospholipase and edema activities of snake venoms and its isolated PLA(2)s by EPema is reported. In vivo tests showed that EPema is able to totally inhibit a Bothrops jararacussu metalloprotease (BjussuMP-I) induced hemorrhage, suggesting interaction of the extract compounds with this high molecular weight protein. The extract did induce neither hemorrhage nor death in mice when administered alone by i.m. route. When administered separately by i.m. route, the extract did not induce death in mice at 12.5--300 mg/kg doses. Other assays demonstrated that EPema was unable to inhibit fibrinogenolytic and coagulant activities of Bothrops atrox venom. Although the mechanism of action of EPema is still unknown, the finding that no visible change was detected in the electrophoretic pattern of snake venom after incubation with the extract excludes proteolytic degradation as a potential mechanism. The search for new inhibitors of venom metalloproteases and DNAases are a relevant task. Investigation of snake venom inhibitors can provide useful tools for the elucidation of the action mechanisms of purified toxins. Furthermore, these inhibitors can be used as molecular models for development of new therapeutical agents in the treatment of ophidian accidents.

The aqueous extract from aerial parts of Bauhinia forficata was able to neutralize the clotting activity induced by Bothrops and Crotalus crude venoms. The clotting time, upon human plasma, induced by B. moojeni venom was significantly prolonged. Clotting and fibrinogenolytic activities induced by isolated thrombin-like enzyme from Bothrops jararacussu were totally inhibited after incubation at different ratios. The extract was not able to neutralize the hemorrhagic activity induced by an Bothrops venoms, but it efficiently inhibited the edema induced by Crotalus durissus terrificus venom and isolated PLA2s. In addition, it did not inhibited the phospholipase A2 activity of Bothrops snake venoms. Interaction studies between Bauhinia forficata extract and snake venoms, when analyzed by SDS-PAGE, did not reveal any apparent degradation of the venom proteins. This extract is a promising source of natural inhibitors of serine-proteases involved in blood clotting disturbances induced by snake venoms.

Scorpion envenoming causes an intense autonomic discharge, leading to a massive release of neurotransmitters, giving rise to several pathophysiological effects. In this work we report the effects of a Bauhinia forficata aqueous extract (BfAE) upon hyperglycemia, glycogenolysis, increase of plasma catecholamines, lethality and changes in serum insulin and plasma electrolytes induced by Tityus serrulatus scorpion venom (TSV). We compare them with the effects of the regular insulin therapy. The following treatments were performed: TSV (500 microg/kg, i.p.); BfAE (1g/kg, p.o.), 24, 12 and 1 h before and immediately after TSV or saline and insulin in a single dose (1.5 IU/kg, s.c.) after TSV. BfAE reduces the fast hyperglycemia induced by TSV, but it is deprived of hypoglycemic activity. The extract also did not reduce either the intense glycogenolysis or the release of catecholamines and did not stimulate the release of endogenous insulin, although causing changes in the electrolyte plasma levels similarly to insulin. Although BfAE and insulin antagonize some effects of TSV, they should be avoided in the treatment of Tityus serrulatus envenoming, since they enhance the lethality of the venom.