Neutralization of the neuromuscular activity of bothropstoxin-i, a myotoxin from Bothrops jararacussu snake venom, by a hydroalcoholic extract of Casearia sylvestris Sw. (gua？atonga)

numerous plants are used as snakebite antidotes in brazilian folk medicine, including casearia sylvestris swartz, popularly known as gua？atonga. in this study, we examined the action of a hydroalcoholic extract from c. sylvestris on the neuromuscular blockade caused by bothropstoxin-i (bthtx-i), a myotoxin from bothrops jararacussu venom, in mouse isolated phrenic nerve-diaphragm (pnd) preparations. aqueous (8 and 12 mg/ml, n=4 and 5, respectively) and hydroalcoholic (12 mg/ml, n=12) extracts of the leaves of c. sylvestris caused facilitation in pnd preparations followed by partial neuromuscular blockade. bthtx-i (20 μg/ml, n=4) caused 50% paralysis after 65±15 min (mean ± s.e.m). preincubation (30 min at 37° c) of bthtx-i (20 μg/ml, n=4) with a concentration of the hydroalcoholic extract (4 mg/ml) that had no neuromuscular activity, such as the control (n=5), prevented the neuromuscular blockade caused by the toxin. this protection may be mediated by compounds such as flavonoids and phenols identified by thin-layer chromatography and colorimetric assays.