ANTIMICROBIAL EVALUATION OF METHANOLIC EXTRACTS OF ANNONA MURICATA LINN LEAVES

Abstract

The in vitroantimicrobial evaluation of the methanolic extract the leaf of Annonamuricata(L) was carried out. A total of eleven (11) bacteria and five (5) fungi were used for the antimicrobial test. The microorganisms included Salmonella typhi(ATCC 14028), Staphylococcus aureus, Pseudomonas aeruginosa, Serratiamarcescens, Bacillus subtilis, Shigelladysenteriae, Escherichia coli, Klebsiellapneumoniae, S. typhi, K.oxytoca, Listeria monocytogenes, Aspergillusflavus, Aspergillusniger,Aspergillusfumigatus,Trichophytonmegatrophytes and Candida albicans. The antimicrobial assay was carried out using agar well diffusion method. The extract showed inhibitory activity against 64% of the bacterial isolates but no antifungal activity. It showed inhibitory activity against 71% of Gram-negative bacteria and 50% against Gram-positive bacteria. The most susceptible organism was Salmonella typhi ATCC14028 with zone of inhibition of 11.67±0.88emm at 25mg/ml to the crude extract and 14.00±1.15bmm to fraction 23Chloroform. The result of antibiotic sensitivity testing showed that the antibiotics demonstrated different degrees of activities against the test organisms with the highest zone of inhibition of 11.67±0.88emm by pefloxacin. The minimum inhibitory concentration (MIC) ranged between 25mg/ml to 30mg/ml except Listeria monocytogenes that had 100mg/ml. The rate of killing reduced gradually from 0hr to 6hrs exceptBacillus subtilis which showed increase from 4hrs to 6hrs. Qualitative phytochemical screening revealed the presence of saponin, tannins, terpenoid, steroids and cardiac glycosides. Quantitative analysis established that saponin was the highest constituent (2.546±0.182bmg/g) of the leaf extract while terpenoid was the least constituent (0.084±0.000amg/g). Infra-red spectra of the purified fractions 23C, 28CM and 33M revealed the presence of Cyano, hydroxyl, amine, amide and carbonyl groups which may confer antibacterial potency on the leaf. The highest zone of inhibition of the extract was 14.00±1.15bmm while that of standard antibiotics was 11.67±0.88emm. Therefore it is established that antibacterial activity of the leaf extract compared well with commercial antibiotics. Annonamuricata leaf is therefore a good phytotheraupetic agent which could be useful in the treatment of some bacterial infections.