Anti-proliferative and antibacterial activity of oleo-gum-resin of Boswellia serrata extract and its isolate 3-hydroxy-11-keto-β-boswellic acid

Abstract

Since time immemorial Boswellia serrata has been a useful traditional plant and its oleo-gum-resin is regularly used as an important constituent in herbal medicines for inflammation, cancer sufferers and cosmetics. This study focuses on the antibacterial and anticancer activities of B. serrata oleo-gum-resin extract, fractions and isolates. Time kill kinetic assay, combination study and ethidium bromide efflux pump inhibitory assay of the leading molecule 3-hydroxy-11-keto-β-boswellic acid (KBA) have been evaluated. The extract, fractions and the isolated molecule have shown anti-proliferative activity in different cancer cell lines, and the inhibition ranged from 13% to 93%. KBA caused anti-proliferative dose-dependent impacts on all human malignant cells (IC50 4.10–37.9 µg/ml). In antibacterial study of the extract, fractions and isolated molecules have shown minimum inhibitory concentration MIC range from 31.25 to 1000 μg/ml against 8 different Gram-positive and Gram-negative bacterial strains. KBA exhibited synergistic effect with a oxacillin against different drug resistant clinical isolates with fractional inhibitory concentration index (FICI) in the range of 0.325–0.450 µg/ml. KBA exhibited bacteriostatic killing mechanism and could also modulate ethidium bromide efflux pump to find its potential in combination therapy against multi-drug resistant Staphylococcal infections. KBA in the extract was quantified using HPLC-PDA and its structure was validated for the first time by X-ray crystallography. This study reinforced the promising treatment of KBA for cancer and S. aureus infections. KBA can be further explored to develop potential lead combinations of anti-cancer and anti-Gram-positive bacterial herbal formulations.