Cytotoxic glucosydic iridoids from Veronica americana

Abstract Fractionation guided by the cytotoxic activity of the methanolic extract of Veronica americana led to the isolation of two new iridoids identified as 4β-hydroxy-6- O -( p -hydroxybenzoyl)-tetrahydrolinaride ( 1 ) and 10- O -protocatechuyl-catalpol ( 2 ), together with four known aromatic acids, veratric acid ( 3 ) p -methoxybenzoic acid ( 4 ), p -hydroxybenzoic acid ( 5 ) and protocatechuic acid ( 6 ). The structure of these compounds was determined by spectroscopic analysis. Iridoid glycosides 1 and 2 showed selective cytotoxic activity against the human cancer cell lines HF-6 (IC 50  = 0.031 and 0.066 μM, respectively) and PC-3 (IC 50  = 0.721 and 0.801 μM, respectively), with less sensitivity in normal MRC-5 cells (IC 50  = 77.103 and 1451.562 μM, respectively). Compound 1 was 9.9 times more potent than camptothecin against HF-6 cell line, while compound 2 was 4.7 times, more potent, against the same cell line, than camptothecin. The found biological efficacy of 1 and 2 allow us to propose these compounds as candidates for the development of effective anticancer therapeutic agents.