Antibacterial activity of a novel fatty acid (14E, 18E, 22E, 26E)-methyl nonacosa-14, 18, 22, 26 tetraenoate isolated from Amaranthus spinosus

Amaranthus spinosus Linn. (Amaranthaceae), commonly known as ''spiny pigweed'', is used in both Indian traditional system and folk medicine for treatment of infectious diseases for a long time in several traditional herbal medicinal preparations. A novel fatty acid [(14E, 18E, 22E, 26E)-methyl nonacosa-14, 18, 22, 26 tetraenoate] is the major metabolite present.This study examines the antibacterial potential of the fatty acid isolated from the A. spinosus against some Gram-positive and Gram-negative bacteria.Three Gram-positive and seven Gram-negative bacterial strains were used for antibacterial assay. The minimum inhibitory concentration (MIC) of the fatty acid was analysed by dilution method and the effects of the fatty acid on the bacterial membrane were studied in detail by flow cytometry analysis.All the studied bacterial strains were found to be inhibited at a concentration of 100 μg/mL. Staphylococcus aureus ML-59, Bacillus lycheniformis 10341, Shigella boydii 8, Vibrio cholera 811, Vibrio cholera 854 and Vibrio alginolyteus were susceptible and sensitive to the tested fatty acid with a MIC value of 25 μg/mL. It proved a full spectrum of antibacterial activity associated with alterations in the permeability of bacterial membranes.The fatty acid from the A. spinosus possesses potent antibacterial action.