Synthesis and antitumor activity of ring A modified 11-keto-β-boswellic acid derivatives

•We investigated a variety of derivatives of 11-keto-β-boswellic acid.•The compounds showed antitumor activity on different human cancer cell lines.•Many of the compounds are cytotoxic even in a low micro mol concentration.•A nitrogen bearing substituent at position C-2 increases cytotoxicity.•Introduction of an additional carboxylic group decreases cytotoxicity.

Beta-boswellic acids are interesting triterpenoic acids that show different biological activities. Their cytotoxic potential, as well as that of their derivates remained unexploited so far. In this study we were able to prepare derivatives of 11-keto-β-boswellic acid that showed lower IC50 values as determined by a sulphorhodamine B (SRB) assay using several different human tumour cell lines. Thus, the introduction of an amino group at position C-2 led to a significantly improved cytotoxic activity of amine 18. An apoptotic effect of compound 18 was determined using DNA laddering and trypan blue staining experiments.

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