ABSTRACT

Diarrhoea, whatever the underlying causes affects both man and animals, and remains a global concern, requiring urgent attention, especially among the young. The quest for a more natural alternative that is easily available, accessible and affordable, have necessitated an increased global search particularly among herbs for bioactive anti-diarrhoeal agents. This study therefore, intended to interrogate the extracts of Anacardium occidentale leaves to confirm earlier claims of possible anti-diarrhoeal activity, then use solvent-solvent partitioning to arrive at varying fractions, and test both extract and fractions to ascertain any active biomolecules, and unearth any probable mechanism of action, in vitro – on isolated rabbit intestines and in microbial cultures of enterobacteria. The results obtained in this work indicated that, potentially safe concentrations of the crude extract and the different fractions had varying degrees of protection from diarrhoea, in dose dependent manners, using various in vivo models. Oral administration of the highest dose (800mg/kg b. wt.), elicited maximal inhibitory effects on all the diarrhoea parameters investigated. In vitro, the results of this study showed that both the crude extract and the different fractions of A. occidentale leaves provoked relaxing effect on acetylcholine- and histamine- induced contractions of isolated rabbit intestinal smooth muscles, which portrayed a concentration dependent effect across the various percentages investigated. It was observed that whereas, both the crude extract and the fractions at all concentrations studied, partially inhibited acetylcholine-induced smooth muscle contractions on isolated rabbit intestines, the histamine receptors where completely blocked, indicating more of an anti-histamine than anti-cholinergic mechanism of controlling diarrhoea for A. occidentale extract. Investigating the role these plant-derived products play on isolates of diarrhoea-causing pathogenic E. coli, and Salmonella spp., the crude extract portends to inhibit the bacterial growth more than any of the derived fractions, thus suggestive of an additive, complementary or synergistic effect of individual composites, rather than the role of a single biomolecule in the leaf extracts of A. occidentale. Again, asides the crude extract, only the chloroform fraction possessed potent active principles with overt anti-diarrhoeal activities on all the parameters employed for this work. In conclusion, the extracts of Anacardium occidentale, have shown good anti-diarrhoeal effects, principally by decreasing intestinal secretions, modifying intestinal motility and inhibition of diarrhoea causing enterogenic E. coli and Salmonella organisms’ growth in vitro, which at least, in part, lends some credence to the folkloric claim that A. occidentale leaves can be used to control diarrhoea, even in emergencies, hence its use in some rural communities for such.