Multifloroside (4), together with 10-hydroxyoleoside 11-methyl ester (1), 10-hydroxyoleoside dimethyl ester (2), and 10-hydroxyligustroside (3), are all secoiridoids, which are naturally occurring compounds that possess a wide range of biological and pharmacological activities. However, the anti-cancer activity of 1-4 has not been evaluated yet. The objective of this work was to study the anti-cancer activities of 1-4 in the human epidermoid carcinoma cell lines A431 and the human non-small cell lung cancer (NSCLC) cell lines A549. The results indicate that 1-4 differ in potency in their ability to inhibit the proliferation of human A431 and A549 cells, and multifloroside (4) display the highest inhibitory activity against A431 cells. The structure-activity relationships suggest that the o-hydroxy-p-hydroxy-phenylethyl group may contribute to the anti-cancer activity against A431 cells. Multifloroside treatment can also inhibit cell colony formation, arrest the cell cycle in the S-phase, increase the levels of reactive-oxygen-species (ROS), and mitochondrial membrane potential (MMP), but it did not significantly induce cell apoptosis at low concentrations. The findings indicated that multifloroside (4) has the tendency to show selective anti-cancer effects in A431 cells, along with suppressing the colony formation, inducing S cell cycle arrest, ROS production, and increasing MMP.
Keywords: 10-oxyderivatives of oleoside secoiridoids; anti-cancer activities; flow cytometry; multifloroside; structure-activity relationship.