Anticrotalic and antitumoral activities of gel filtration fractions of aqueous extract from Tabernaemontana catharinensis (Apocynaceae)

Abstract

The high mortality caused by Crotalus durissus terrificus snake venom is mainly due to crotoxin, which acts on the neuromuscular junction inhibiting the mechanism mediating acetylcholine release, thus leading to motor and respiratory paralysis and subsequently to animal death. We recently demonstrated that the aqueous extract (AE) of Tabernaemontana catharinensis can inhibit the lethal activity of C. d. terrificus venom. Eight fractions, P I to P VIII, were obtained by gel filtration of the extract on Sephadex G-10, and assayed for lethality and cytotoxicity. Fraction P VII [2.0 mg/100 g rat/50 μl saline solution (ss)] injected intramuscularly (i.m.) 20 s after the venom (240 μg) or crotoxin (200 μg/50 μl ss) neutralized the lethal activity of 2 LD 50 of both. Fractions P I, P VI and P VIII (5.0 mg/100 g rat/50 μl ss) presented potent antitumoral activity in vitro against cells from human breast carcinoma (SK-BR–3) after 24 h incubation, as measured by Mosmann colorimetric method. Fraction P VII contains 12-methoxy-4-methylvoachalotine as its major component. These results demonstrate that the antivenom and antitumoral activities of the AE of T. catharinensis are exerted by different substances present in fraction P VII and fractions P I, P VI and P VIII, respectively , whose characteristics are distinct in terms of staining and Rf when analyzed by thin layer chromatography. The results also show that a preliminary fractionation by Sephadex G-10 gel filtration is a good option as a first step for isolation of biologically active substances from T. catharinensis.