Antiproliferative Effects of Nerium oleander Leaves and Their Cardiac Glycosides Odoroside A and Oleandrin on MCF-7 Cancer Cells

Abstract

Nerium oleander leaves extract preparations have been used for centuries against sores, abscesses and solid tumors. The aim of this study was to identify active compound(s) responsible for the antiproliferative activity of N. oleander leaves against MCF-7 breast cancer cell line and to explore their mechanisms of action. The methanolic extract and fractions were screened against four human cancer cell lines: HT-144, MCF-7, NCI-H460 and SF-268 using sulforhodamine B assay. The most active ethyl acetate soluble fraction led to the isolation of eleven pure compounds viz adynerigenin, adynerin, odoroside A, odoroside B, 5-Okaempferobinoside, β-neriursate, oleanderocioic acid, oleandiginoside, oleandrin, 5-Oquercetibinoside and ursolic acid. The methanolic extract and the ethyl acetate soluble fraction exhibited significant growth inhibition (TGI: 0.14 to 3.3 µg/ml) against HT-144, MCF-7, NCI-H460 and SF-268 cell lines. The effects of the methanolic extract, ethyl acetate soluble fraction, odoroside A and oleandrin on the cytoskeleton and nuclei of MCF-7 cells were evaluated using immunofluorescence microscopy. Significant reduction in the mitotic index of MCF-7 cells were exhibited by the methanolic extract, ethyl acetate soluble fraction, odoroside A and oleandrin accompanied by morphological changes such as band-like arrangement of cells, reduction in F-actin processes, disruption of interphase microtubule network and condensation of nuclei. These results support that the N. oleander leaves possess antiproliferative activity against the aforementioned cell lines particularly estrogen receptor positive MCF-7 cells, thereby justifying its traditional use against tumors. Moreover, the antiproliferative effects induced by the methanolic extract, ethyl acetate soluble fraction, odoroside A and oleandrin were possibly related to skeletal and nuclear morphological changes.