Abstract
Beta-boswellic acids are considered the main bioactive components of frankincense. Their potential to act as cytotoxic agents, as well as that of their derivatives remained unexploited so far. In this study we were able to prepare derivatives of 11-keto-β-boswellic acid (KBA) that showed lower IC50 values as determined by a sulphorhodamine B (SRB) assay using several different human tumour cell lines. Monodesmosidic saponins of KBA are as cytotoxic as 3-acetyl-KBA. The presence of a free hydroxyl group at position C-3 seems to lower cytotoxicity while the presence of an amide function at C-24 improves cytotoxicity. The most active compound of this series gave IC50 values as low as 4.5 μM. Cell death proceeded mainly via apoptosis.
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•A variety of 11-keto-β-boswellic acid derivatives was investigated.•The compounds showed antitumor activity on different human cancer cell lines.•Many of the compounds are cytotoxic even in a low micro mol concentration.•An amide at position C-24 increases cytotoxicity.•Monodesmosidic saponins showed an increased cytotoxicity.