Biologically active flavonoid glycosides from Horwoodia dicksoniae Turrill

Three flavonoid glycosides and one aglycone have been isolated from the ethanolic extract of Horwoodia dicksoniae Turrill for the first time, and their structures were assigned from ¹H- and ¹³C-NMR spectra (DEPT) and from negative ESI-MS, as luteolin-7-O-β-D-glucopyranoside (1), apigenin-6-C-β-D-galactopyranoside (2), luteolin-6-C- β-D-galactopyranoside (3) and luteolin (4). The SRB cytotoxicity assay was used to investigate the antitumor activities of the ethanolic extract, compounds 1, 3 and 4. Compound 1 showed the highest cytotoxic activity against the three human cell lines; HEPG2, HCT 116 and MCF 7 (IC₅₀=10.7, 9.3 and 9.9µg/ml, respectively), compared with the standard antitumor drug doxorubicin. Compound 4 showed selective antitumor activity against the colon cell line (IC₅₀=9.5µg/ml). The present investigation also demonstrates the protective effect of compounds 1, 3 and 4 with antioxidant potential, in glycerol-induced myoglobinuric acute renal failure in rats. Treatment with each of these compounds attenuated renal dysfunction, and restored the oxidant balance by decreasing renal MDA levels, increasing the activity of the depleted renal antioxidant enzymes, and the non enzymatic antioxidant GSH. They also, decreased the elevated serum inflammatory marker (TNF- α), and ameliorated apoptotic kidney damage by reduction in caspase-3 activity. Compound 1 showed the highest biological activity.