Objective: The antibacterial principle of Avicennia marina L stem extract was determined by agar well diffusion method followed by GC-MS,1H NMR and 13C NMR.Methods: Methanol was used as the solvent for the isolation of bioactive principle from the stem of Avicennia marina L. Agar well diffusion method was used to screen the antibacterial activity and FRAP method was employed to determine the antioxidant activity for raw and crude extract as well as the purified compound. GC-MS followed by 1H NMR and 13C NMR were used to elucidate the compound responsible for the antibacterial and antioxidant activity.Results: The degree of antioxidant and antibacterial activity differs between raw extract, crude extract and the pure compound. The antioxidant activity is more crude extract (p<0.05) and the antibacterial activity is more of pure compound (p<0.05) than the standard antibiotic gentamicin. GC-MS followed by 1H NMR and 13C NMR revealed that the compound is 2-propenoicacid, 3-(4-hydroxy-3-methoxyphenyl)- also called ferulic acid.Conclusion: The stem extract in methanol shows potential antibacterial and antioxidant activity. It is due to presence of ferulic acid in methanol extract in 14th fraction.Â
