Antimicrobial activity and anti-diarrheal potentials of <i>Psidium guajava</i> Linn leaf extract in experimental rat models

Abstract

This study evaluated the antimicrobial activity and antidiarrheal potentials of guava leaf ethanol extract (GLEE). GLEE prepared from dried guava leaves was first subjected to acute toxicity (LD50) test. Antimicrobial activity of GLEE was tested in vitro against some enteropathogenic organisms including Escherichia coli, Cympylobacter jejuni, Salmonella typhi, Shigella dysenteriae and Staphylococcus aureus. The zone of inhibition for each GLEE application was determined using Agar well diffusion techniques, while the minimum inhibitory concentration (MIC) was determined by doubling dilution technique compared with Ciprofloxacin. The anti-diarrheal effect of GLEE was evaluated using charcoal meal transit and castor oil induced diarrhea models in rats. For each model, 36 Wistar rats assigned 4 groups of 3 rats, replicated thrice and treated according to the order: group 1(control), group 2(0.5 mg/kg Loperamide), groups 3 and 4 (500 and 1000 mg/kg of GLEE respectively) were used. Results obtained indicated an LD50 value >5000 mg/kg for GLEE. GLEE also significantly inhibited microbial growth in concentration dependent pattern (p<0.05) with the highest concentration producing inhibition zones measuring 9, 13, 14, 17 and 17 mm against S. dysenteriae, S. aureus, S. typhi, E. coli and C. jejuni respectively. In the castor oil induced diarrhea model, GLEE significantly reduced frequency and weight of wet stool output in rats, and also inhibited charcoal meal transit significantly in the motility study. In both cases, the activities of GLEE compared favourably with that of Loperamide, the standard drug used. These results therefore justify the local use of guava leaf for the treatment of diarrhea.