Abstract

Carissa edulis Vahl (Apocynaceae) is used commonly in Northern Nigeria for the treatment of various microbial infections such as venereal, upper respiratory, skin and gastro-intestinal. The antimicrobial activity of the water extracts of the leaves and fruits were screened using Staphylococcus aureus, NCTC 6571,Escherichia coli NCTC 10418, Pseudomonas aeruginosa NCTC 6750 andBacillus subtilis NCT 10342. The gram positive organisms, B. subtilis and S. aureus were more susceptible than the gram negative organisms, E. coli and P. aeruginosa. The leaves extract was more active than that of the fruits extract. The minimum inhibitory concentration for E. coli and B. subtilis was 4.0% w/v of the fruits aqueous extract while that of the leaves was 3.0% w/v for the same organisms. B. subtilis was killed at a faster rate than E. coli. A percentage kill of 99.52% was obtained for B. subtilis and 91.36% for E. coli with the leaves extract as compared to that of the fruits extract where a percentage kill of 93.6% was obtained for B. subtilis and 56.4% for E. coli at 120 min. The results of this work justify the use of the plant in the treatment of microbial infections in ethno medicine.    

Key words: Carissa edulis, water extract, fruits, leaves, antimicrobial.