COMPARATIVE EVALUATION OF THE ANTIMICROBIAL ACTIVITY OF METHANOLIC AND AQUEOUS JUGLANS REGIA L. BARK EXTRACTS AGAINST BACTERIAL AND FUNGAL PATHOGENS

Abstract

The comparative antibacterial and antifungal activity of methanolic and aqueous bark extracts of J. regia from Upper Dir, Khyber Pakhtunkhwa, Pakistan was evaluated. Three different concentrations (30, 60, 90 mg/mL) of J. regia extracts were tested on four bacterial and four fungal strains using agar well diffusion and minimum inhibitory concentration (MIC) methods, respectively. The antimicrobial activity of both extracts was concentration-dependent, with different efficiencies against different microorganisms. The methanolic extract showed more antibacterial activity with an inhibition zone of 18-22 mm at 90 mg/mL, whereas the aqueous extract showed an inhibition zone of 8-18 mm at 90 mg/mL. Two-way ANOVA results confirmed that there were significant differences in antibacterial activity between the type of extract and concentrations for all the microorganisms (p < 0.001), while only for Escherichia coli there was a significant interaction between extract type and concentration (p = 0.031). The antifungal activity was more species-dependent, with the aqueous extract being more active against Aspergillus niger, Candida albicans and Trichophyton rubrum at 90 mg/mL, while methanolic extract was more active against Fusarium oxysporum. Significant type × concentration interactions were found for all fungi (p ≤ 0.001). The methanolic extract consistently showed lower MIC values than the aqueous extract. The antimicrobial activity of J. regia bark was generally considered to be significant, and the results were related to the extraction solvent, concentration and type of microorganism. More phytochemical and mechanistic research should be conducted in methanolic and aqueous extracts to determine the compound responsible for this activity.