Hexane (HEX), dichloromethane (DM), ethyl acetate (EA) and methanol (M) extracts (0.1, 0.2 and 0.4mg/ml) were obtained via Soxhlet from Plathymenia reticulata barks (Pr). These extracts were evaluated against the myotoxicity (58%) and the irreversible in vitro neuromuscular blockade of Bothrops jararacussu (Bjssu) venom (40μg/ml) in a mouse phrenic-nerve diaphragm preparation, by using light-microscopy and conventional myographic techniques. Thin layer chromatography (TLC) was used to access the basic composition of extracts. The efficacy of the extracts was analyzed by Student's t-test or repeated measures ANOVA. The significance level was set at 5%. The Pr extracts showed a higher polyphenols content (3.75%), from which tannins take part, around 20 times more than flavonoids content (0.16%). Qualitatively, via TLC, DM and EA extracts showed higher tannins concentration than the HEX and M extracts. Pharmacologically, at 0.4mg/ml, DM was more effective (92 ± 6.2%) than EA (81.3 ±10%) = HEX, 77.2 ±4.7%) > M (54 ±10%) against the toxic effects of the venom. Morphologically, DM extract preserved intact 52.8% of the muscle fibers in the presence of the venom. We concluded that P. reticulata extracts are able to inhibit toxic effects of B. jararacussu venom, whose protective mechanism could be mediated by tannins.
Keywords: Bothrops jararacussu; Plathymenia reticulata; flavonoid; neuromuscular preparation; polyphenol; snake venom; tannin.