In vitro apoptotic bioactivity of flavonoids from Astragalus verrucosus Moris

Abstract

Six aglycone flavonoids and their corresponding glycosides: genistein and genistin, quercetin and rutin, apigenin and apigenin 7-O-β-D-(6-p-coumaroyl) glucoside, as well as the aglycone daidzein isolated from Astragalus verrucosus Moris, were tested for their apoptosis-inducing potential. In vitro techniques that monitor bioactivity through morphological and biochemical changes were carried out on HCT116 (human colon carcinoma) and MCF7 (human Caucasian breast adenocarcinoma) cancer cell lines. Dose-dependent cytotoxic effects were monitored through changes in mitochondrial dehydrogenase activity using the standard MTT assay. The median inhibitory concentration (GI50) determined from the dose-response curves showed that the aglycones apigenin and quercetin were the most bioactive (low GI50), whilst daidzein and genistein, which had not been previously tested on these cell lines, showed a smaller cytotoxic effect (high GI50). The remaining flavonoids, mostly glycosides, showed negligible cytotoxicity. Morphological changes were monitored by microscopic observation with a photographic record. Results showed important hallmarks of apoptosis, including cell rounding with reduction of cell volume, small condensed nuclei, membrane blebbing and formation of apoptotic bodies.