COMPARATIVE STUDY ON ANTIMICROBIAL ACTIVITIES OF MANGROVES GROWING IN POLLUTED AND NON-POLLUTED SITES OF NORTHERN ARABIAN SEA

The aims of this study were to evaluate and compare the antibacterial and antifungal activities of botanicals extracted using 70% methanol from leaf, bark and pneumatophore/root of four different species of mangroves growing in different polluted and non-polluted sites along the Northern coast of Arabian sea. Plants produce bioactive compounds under stress, therefore in-vitro activities of extracts of mangroves growing in polluted (Avicennia marina) and non-polluted (A. marina, Aegiceras corniculatum, Rhizophora mucronata and Ceriops tagal) sites were assessed. Activities were performed against five Gram-positive and seven Gram-negative bacteria and twelve fungi including ten molds (eight saprophytes and two dermatophytes) and two yeasts. Well diffusion and disc diffusion methods were used in case of bacterial strains and former was found more efficient, therefore, it was used for analyzing fungal strains. Dilution method was used for the determination of the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC) of extracts. MIC values were observed from 0.3125 to 40 mg/mL. MIC value of 0.3125 mg/mL was observed from bark of A. corniculatum (NBCA) against Pseudomonas aeruginosa. Various botanicals showed MIC value of 1.25 mg/mL against different species of bacteria. In general leaf extracts were comparatively more active and antibacterial spectrum of extracts from R. mucronata was broader. In case of antifungal activity, MIC values were ranging from 5 to 20 mg/mL. MIC value of 5 mg/mL was observed in various tests, including extracts obtained from non-polluted bark of A. marina (NBMA, against Aspergillusniger and Fusariumoxysporum); NBCA, against A. niger and Candida albicans; roots of A. corniculatum (NRCA, against A. niger and Chrysosporiumsp); polluted pneumatophores of A. marina (PPMA against Paecilomycesvariotii and Aspergillusterreus); polluted bark of A. marina (PBMA against Penicilliumsp). Polluted leaf (PLMA) and non-polluted pneumatophores (NPMA) of A. marina, and roots of C. tagal (NRTC) also showed MIC, 5 mg/mL against C. albicans. In general root extracts were more active and Aegicerascorniculatumshowed broader spectrum. A. marina was the only mangrove found growing both in polluted and non-polluted habitat. Polluted stands of A. marina showed broader and higher antibacterial and antifungal activity indicating that the pollution stress has stimulated the physicochemical changes to produce botanicals responsible for antimicrobial activity.