The present invention relates to s pharmaceutical composition for the treatment of multi-drug resistant infections comprising benzopyrano[3,4-b][1]benzopyran-12(6H)-one class of compound boeravinone B of formula 1 in combination with antimicrobial agent. The present invention particularly relates to the potentiation of the bio-efficacy of anti-infective drugs, when used in combination with boeravinone B. The present invention further relates to the use of boeravinone B to overcome the resistance or multi-drug resistance developed by bacteria against quinolone, mupirocin and macrolide class of anti-bacterial agents via inhibition of bacterial efflux pumps. In addition, the invention relates to methods of using compounds for treating or preventing drug-resistant bacterial diseases.
