Antimicrobial effect of Albizia Zygia DC leaf extracts on some selected micro organisms
This study investigated the antimicrobial activities of methanolic, ethanolic and aqueous leaf extracts of Albizia zygia on some selected bacteria and fungi with a view to determining the possibility of harnessing the antimicrobial potential of the leaf as a cheaper substitute for conventional synthetic antibiotics. The antimicrobial activities of Albizia zygia leaf extract on the test organisms was carried out using disc diffusion technique on Mueller Hinton agar and Potato Dextrose Agar for bacterial and fungal assay, respectively. The bored wells on agar plates previously seeded with standardized bacteria and fungal spores were filled with different concentrations (30 and 50mg/ml) of the extracts (Methanolic, ethanolic and aqueous) and incubated at 37 ºC for 24 h for bacteria and 28 ºC for 5 d for fungi. The diameters of zones of inhibition were measured. The minimum inhibitory and minimum bacteriocidal concentrations were equally determined using agar dilution method. The chemical group constituents present in the crude leaf extract were also monitored. The death rate of some selected bacteria by the methanolic leaf extract was determined as welll as the protein and the potassium leakage from the bacterial cell. The cytotoxicity effects of the methanolic leaf extract on mice were monitored. The effect of the methanolic leaf extract on the metabolic activities (enzymes) Aspartate transaminase (AST) and Alanine transaminase (ALT) were also assessed using Randox enzyme kit. The antibacterial sensitivity test showed that the extract was effective against both Gram-positive and Gram-negative bacteria, indicating the broad-spectrum antibiotic activity of the extract. The diameter of zones of inhibition ranged from 3 to 25 mm. The ethanolic and aqueous extracts had little or no effect on the bacterial isolates at the concentrations used. The antibacterial activity of the methanolic extract compared favorably with the reference antibiotic (streptomycin) used. All the extracts showed no antimicrobial activity on fungal isolates. The chemical groups inherent in Albizia zygia were alkaloids, flavonoids, tannins, saponins and anthraquinone. The lowest Minimum Inhibitory Concentration (MIC) (3.75 µg/ml) of the plant extract was observed in Clostridium sporogenes while the highest MIC value (15.5 µg/ml) was observed in Bacillus subtilis. The Minimum Bactericidal Concentration (MBC) of the plant extract ranged from 7.5 µg/ml for Clostridium sporogenes to 30 µg/ml for Bacillus subtilis. The highest percentage of bacteria killed was 100% in Bacillus cereus treated with 60 µg/ml of methanolic extract at 120 min. The lowest percentage of bacteria killed was 28% and was observed in K. pneumoniae treated with 7.5 µg/ml of the extract at 120 min. The amount of protein and potassium ion detected in solution after treatment of the bacterial cells with the plant extract increased gradually with time for both Bacillus subtilis and Klebsiella pneumoniae. The highest amounts of protein and potassium ion leakages observed in Bacillus cereus were 40 µg/ml and 400 ppm respectively. The highest amounts of protein and potassium ion leakages observed in Klebsiella pneumoniae were 10.02 µg/ml and 370 ppm respectively. Enzymatic studies revealed that the leaf extract at high concentrations had negative effect on the enzymes aspartate transaminase (AST) and alanine transaminase (ALT) in the liver of the mice as the levels of these enzymes were found to increase significantly in serum (ALT 69.23 IU/ml and AST 168.45 IU/ml) but reduced drastically in the liver (ALT 30.61 IU/ml and AST 137.57 IU/ml). The levels of ALT and AST increased in the kidney with corresponding decrease in the serum confirming that the leaf extract does not have any lethal effect on the mice' kidney The study concluded that the methanolic extract of A. zygia showed better activities only on the bacterial isolates, hence could be formulated for emperical therapeutic measures against infections caused by the susceptible test bacteria.