Majoranaquinone exhibits a high antibacterial effect against 4 Staphylococcus , 1 Moraxella , and 1 Enterococcus strains. Majoranaquinone shows substantial efflux pump inhibitory activity in Escherichia coli ATCC 25922 strain. Majoranaquinone is found to be an effective biofilm formation inhibitor on E.coli , ATCC 25922 and E. coli K-12 AG100 bacteria.