Reversal of Coumarin-Induced Toxicity by the Extracts and Fractions of Ageratum conyzoides

Abstract: This study examined the antidotal effects of the methanol extract (MeOH) and fractions of Ageratum conyzoides L. (Asteraceae) on coumarin-induced toxicity in rats. The effects of these extracts on coumarin acute toxicity (LD 50 ) and mortality rate were assessed. The LD 50 of coumarin was increased by as much as 487.2 and 238.1% when co-administered with the MeOH extract (1 g/kg) and the methanol fraction, (MF) (1 g/kg) respectively. The MeOH extract and MF significantly (p#0.05) reduced coumarin-induced mortality to 0 and 40%, respectively when compared to the 100% mortality recorded for the control group. Vitamin K and activated charcoal, which were used as standard antidotes, also produced similar reductions in percentage mortality, but MeOH extract and MF performed better. The Hexane Fraction (HF) and the ethyl acetate fraction, (EF) did not significantly (p>0.05) affect coumarin-induced mortality. Maximal antidotal effect was recorded when MeOH extract was given within 3 h of coumarin administration. The MeOH extract and the MF demonstrated antidotal activities against acute poisoning by coumarin in rodents. On their own, the extracts did not produce any gross pathological change in the animals, and could therefore be harnessed as useful antidote in coumarin poisoning. Local activities of the phytoconstituents of A. conyzoides on the GIT which limits absorption and haemorrhagic damages are believed to be responsible for the reversal of the coumarin toxicity