Synthesis of Cycloartan-16β-ol from 16β 24R-Epoxy-Cycloartane and their Cytotoxicity Evaluation against Human Cancer Cell Lines.

It was found that Argentatins A and B triterpenoids make up approximately 20-30 % of the waste resin produced from the industrial processes to isolate rubber from P. argentatum. We have developed an efficient protocol for synthesizing cycloartane-16β-ol derivatives by opening the oxepane ring of argentatin B acetate (2) with BF3-OEt2. Although three new cycloartenol derivatives showed high cytotoxicity against PC-3 and HCT-15 cancer cell lines, nevertheless, the best results were obtained for (16β,24R) -(16,24-epoxy-cycloartan-2(1H)-ylidene) acetate (14), compound with intact oxepane ring. These results indicate that the substituents in the argentatin nucleus and a side chain account for the cytotoxic activity. However, according to the selectivity index (SI), 14 did not show selectivity activity to cancer cell lines over the HaCat noncancerous cell line. The compound 3β,16β-Dihydroxy-cycloartan-24-one (5), synthesized by oxepane opening, demonstrated high cytotoxic activity to cancer cell lines and showed a remarkable selectivity to cancer cell lines over the noncancerous ones. These results suggest that 5 could lead to the development of new anticancer compounds.