Comparative phytochemical screening and antimicrobial activity of the aqueous and methanol leaf and bark extracts of Carica papaya

The leaves and bark of Carica papaya (Pawpaw) were subjected to solvent extraction using both water and methanol. Preliminary phytochemical evaluation of the extracts was performed followed by antimicrobial studies against some bacteria using the agar-well diffusion method. The phytochemical analysis showed that the extracts contained alkaloids, saponins, tannins and flavonoids. The methanol extracts were observed to be more active than the aqueous extracts and the leaf extracts had higher antimicrobial effect at all working concentrations than the bark extracts. The zones of inhibition for the methanol leaf extract against Staphylococcus aureus, Bacillus subtilis, Enterobacter aerogenes and Pseudomonas aeruginosa at 200 mg/ml concentration were 45.50±1.125, 44.00±0.893, 31.00±1.106, and 38.00±0.625 mm respectively while those of the bark extracts for the above mentioned organisms were 42 50+1.125, 41.00+0.0803,3.00+ 1.016 and 0.00 mm respectively. The aqueous bark extract did not show significant activity. All the extracts showed activity against the test organisms except Escherichia coli where no zone of inhibition was produced. Staphylococcus aureus showed the highest zones in all the extracts followed by Bacillus subtilis and Enterobacter aerogenes while Pseudomonas aeruginosa was the least sensitive. All the extracts demonstrated higher activities against the Gram-positive than the Gram-negative bacteria tested. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the leaf and bark extracts ranged between 25 – 200 mg/ml.KEYWORDS: Carica papaya, phytochemical properties, MIC, antimicrobial.