ABSTRACT
Traditional medicine is a popular form of therapy in developing countries and its use is widely documented in various literatures due to its huge potential in the discovery of novel therapeutic molecules. This present research was done to study the antimicrobial activity of crude extracts of the leaves and roots of Petiveria alliacea, Ocimum gratissium and Annona muricata. The stem and leaves of Petiveria alliacea (guinea hen), Ocimum gratissium (scent leaf) and Annona muricata (graviola leaf) used for the research were collected from a farmland in Benin City, Edo State, Nigeria. Phytochemical screening of leaves of Petiveria alliacea showed the presence of flavonoids, tannins, cardiacglycosides, saponins, steroids, terpenoids, alkaloids, coumarines and reducing sugar while tannins, saponins and steroids were not detected in the stem. For Annona muricata, the stem and leaves showed the presence of tannins, cardiacglycosides, terpenoids, alkaloids, coumarines and reducing sugar while the leaves showed the presence of flavovoids, in addition to other metabolites. For Ocimum gratissium, the stem and leaves showed the presence of flavonoids, tannins, cardiacglycosides, terpenoids, alkaloids and reducing sugar while the leaves showed the presence of steroids, in addition to other metabolites. The result of the zone of inhibition of the aqueous, ethanolic and methanolic extracts of Ocimum gratissium, P. alliacea, and A. muricata leaves against six pathogenic bacteria isolates revealed that the highest zone of inhibition was exhibited by ethanol extract for the six pathogenic organisms for the three plants. For aqueous, there was zone of inhibition for staphylococcus sp. only at 0.1g/ml, Klebsiella sp., Shigella sp., Proteus sp. and Salmonella sp. did not exhibit any zone of inhibition. For antimicrobial activity, the extract of ethanol recorded moderate growth at concentrations of 25mg/ml, 12.5mg/ml and 6.25mg/ml, while methanol recorded scanty to moderate growth at 12.5mg/ml and 6.25mg/ml. The highest activity of Petiveria alliacea was against Proteus sp. at concentration of 25mg/ml for ethanolic extract and its lowest activity was against Klebsiella sp. The highest zone of inhibition recorded by Petiveria alliacea was 7.62 ± 0.45mm while its lowest diameter of inhibition was 2.20 ± 1.00mm. The result of antimicrobial activity of methanolic extract of A. muricata on the pathogenic bacteria showed decreased average zone of inhibition with decreased concentration of the extract, that is, the lower the concentration, the lower the antibacterial activity. The result of the MIC of aqueous, ethanolic and methanolic extracts of leaves against the six pathogenic bacteria isolates revealed that 50mg/ml prevented growth against the pathogens tested. The results obtained in this study showed that the test organisms were susceptible to the aqueous and methanolic extracts of O. gratissium leaf which contains phytochemicals that possess antibacterial property and could be used as potential source of natural product in industrial manufacturing of drugs, for the treatment of infections/diseases caused by E. coli. However, the toxicity and the side effects of the plant leaf extract need to be determined. Furthermore, there is a need for further investigation into the non-susceptibility of test organisms to the ethanolic extract of the plant.
