Isolation of antibacterials from the mangrove, Avicennia marina and their activity against multi drug resistant Staphylococcus aureus

ABSTRACT

Objective: leaf extract of A. marina was tested on the growth of clinically isolated multi-drug resistant Staphylococcus aureus and its bioactive compounds were attempted. Method: Clinical strain of Staphylococcus aureus, were isolated from sputum, pus and blood of different patients and 22 strains were screened for antibiotic susceptibility. Avicennia marina was extracted in different solvents and antibacterial assay was carried out using Kirby-Bauer’s disk diffusion method. Crude methanol extract of the mangrove was loaded on a silica gel column and eluted with chloroform and methanol (91 to 19) followed by ethyl acetate and methanol (91 to 19). Based on in vitro assay, the 12th fraction was subjected for minimum inhibitory concentration (MIC). The active fraction was analysed by using a Clarus 500 Perkin Elmer gas chromatography. Result: Based on the antibiotic susceptibility test, six strains (RMSA 6, RMSA12, RMSA16, RMSA18, RMSA19 and RMSA21) were resistance against methicillin, vancomycin and ciprofloxacin. The results indicated that the methanolic leaf extract showed the highest antibacterial activity against all the tested strains RMSA 6 (16mm), RMSA12 (15 mm), RMSA16 (13 mm), RMSA18 (10 mm), RMSA19 (17 mm) and RMSA21 (16 mm). The MIC of the partially purified extract showed potential results against all the multidrug resistant strains however, the lowest concentration was recorded against RMSA 6, RMSA19 and RMSA21 strain. In the GC-MS results, 5 bioactive compounds were identified from the partially purified extract of A.marina. Conclusion:The methanolic extract of A. marina has the more potential candidate to inhibit against multidrug resistant S. aureus.