Evaluation of Antimicrobial Activities of Albizia zygia DC Leaf Extracts against Some Clinically Important Pathogens

Abstract

In vitro antimicrobial effects of aqueous, ethanolic and methanolic extracts of Albizia zygia dc leaf against some clinically important bacterial and fungal pathogens were reported. Following extraction of air dried A. zygia dc leaf by different solvents (water, ethanol and methanol), the filtrates were concentrated in vacuo using rotary evaporator. The antibacterial and antifungal activities were assayed by agar diffusion method on Muller-Hinton Agar (Himedia Laboratories Pvt. Ltd, Vadhani) and Potato dextrose agar (Oxoid, Ltd, Bashingstoke, Hampshire, England) plates, respectively. Standard methods were used to determine the time-kill assay of methanolic extract, the amount of protein and potassium ion leaked in the test bacteria. All the extracts (aqueous, ethanolic and methanolic) did not possess any antifungal property. The aqueous and ethanolic extracts were not active against the test bacteria.  Methanolic extract showed significant antibacterial effect on greater percentage of the test bacteria with diameter of zones of inhibition ranging from 3.0 to 21.12 mm at 30 mg/ml and 5.2 to 25.4 mm at 50 mg/ml of the extract. The minimum inhibitory concentration (MIC) of the methanolic extract ranged between 3.75 and 15.3 mg/ml. The methanolic extract of A. zygia leaf showed a significant bactericidal and bacteriostatic activity against Bacillus subtilis and Klebsiella pneumoniae over the time range (15-120 min) at different MIC concentrations. The time-kill assay of methanolic extract of A. zygia against K. pneumoniae was dose dependent. The amount of protein leaked was higher in B. subtilis than K. pneumoniae at 30 µg/ml (P = 0.05). There was no significant difference in the level of  K⁺ leaked at 15 µg/ml (1 X MIC) and 30 µg/ml (2 X MIC) of the extract.

The methanolic leaf extract of A. zygia showed a considerable inhibitory effect on greater percentage of the test bacterial pathogens, but did not possess antifungal property. The antibacterial potential could be harnessed in the folklore management of infections caused by the susceptible test bacteria.