Selective cytotoxicity and antioxidant effects of compounds from dioscorea membranacea rhizomes

Abstract

Bioassay-guided isolation was used to separate the active ingredients of the ethanolic extract of Dioscorea membranacea by testing cytotoxic activity against three human cancer cell lines, i.e. large cell lung carcinoma (COR-L23), colon cell line (LS-174T) and breast cancer cell line (MCF-7), and two normal human cell lines, keratinocytes (SVK-14) and normal human fibroblasts (HF) using the SRB assay. The DPPH test for antioxidant activity was also employed, as was a test for LDH release as an indicator of damage to the cell membrane. Eight compounds were isolated, two naphthofuranoxepins (dioscorealides A [1] and B [2]), a 1,4-phenanthraquinone (dioscoreanone [3]), three steroids (p-sitosterol [4], stigmasterol [5] and p-D-sitosterol glucoside [8)) and two steroid saponins diosgenin-(3-0-a-L-rhamnopyranosyl (l->2)-P-D-glucopyranoside [6] and diosgenin 3-O-p-D-glucopyranosyl (l->3)-P-glucopyranoside [7]). Cytotoxic activity of 2, 3 and 6 was shown against three cancer cell lines, and 2 showed selective cytotoxic activity against lung and breast cancer, but was less active against the two normal cells, and was not toxic to cell membranes in the LDH assay. The highest antioxidant activity was shown by 3.