Cytotoxic Cardenolides from the Leaves of Acokanthera oblongifolia.

Three previously undescribed cardenolides, acovenosigenin A 3- O - α -L-acofriopyranoside (1), 14-anhydroacovenosigenin A 3- O -[ β -D-glucopyranosyl-(1″→4′)- O - α -L-acofriopyranoside] (2), and 14-anhydroacovenosigenin A 3- O -[ β -D-glucopyranosyl-(1″→4′)- O - α -L-acovenopyranoside] (3), together with the two already known ones, 14-anhydrodigitoxigenin 3- O - β -D-glucopyranoside (4) and acospectoside A (5), were isolated from the leaves of Acokanthera oblongifolia. The influence of cardenolides 1 – 3 and acovenoside A (found in the Acokanthera genus) on three cancer cell lines (HT29, HCT116, and AGS) was also investigated. The most promising results, in comparison with oxaliplatin, were obtained for compound 1 , which was found to be highly cytotoxic for all tested cell lines, HT29 (IC50 = 63.49 nM), HCT116 (IC50 = 67.35 nM), and AGS (IC50 = 80.92 nM). Unfortunately, 1 also showed similar toxicity towards normal lymphocytes (IC50 = 98.03 nM). [ABSTRACT FROM AUTHOR]