Srisopa Ruangnoo

Isolation and characterization of a new cytotoxic dihydrophenanthrene from Dioscorea membranacea rhizomes and its activity against five human cancer cell lines.

ETHNOPHARMACOLOGICAL RELEVANCE The rhizomes of Dioscorea membranacea Pierre (DM) have been used as ingredients in anticancer herbal formulations in Thai traditional medicine (TTM). Thus, the aim of this study was to investigate the active constituents of DM for cytotoxic activity in order to support its TTM use. MATERIALS AND METHODS A bioassay-guided isolation procedure was used to separate the cytotoxic constituents from ethanolic extract of Dioscorea membranacea rhizomes by testing against five human cancer cell lines, i.e. large cell lung carcinoma, COR-L23; liver cancer cells, HepG2; prostate cancer cells, PC3; breast cancer cells MCF-7; cervical cancer cells, Hela; and one normal human lung cell line (MRC 5) using the SRB assay. RESULTS Two known dihydrophenanthrene compounds [2,4 dimethoxy-5,6-dihydroxy-9,10-dihydrophenanthrene (1) and 5-hydroxy-2,4,6-trimethoxy-9,10-dihydrophenanthrene (2)], and a new dihydrophenanthrene compound, 5,6,2 -trihydroxy 3,4-methoxy, 9,10-dihydrophenanthrene (3) were isolated and fully characterized. 1 showed the highest cytotoxic activity against COR-L23, MCF-7 and PC3 cell lines (IC₅₀=14.89, 17.49 and 19.04 µM, respectively), and 2 showed selective cytotoxic activity against PC3 (IC₅₀=23.54 µM). The new compound 3 showed selective cytotoxic activity against only MCF-7 cells (IC₅₀=31.41 µM). Interestingly the crude extract of DM was much less toxic to the normal cell line (MRC-5) (IC₅₀>50 µg/ml) compared to the five cancer cell lines, (IC50 value ranged between 6 and 29 µg/ml). CONCLUSION The phytochemicals isolated from DM may serve as lead compounds for the design of new anti-cancer agents with better selective cytotoxic indices.

A novel steroid and cytotoxic constituents from Dioscorea membranacea Pierre against hepatocellular carcinoma and cholangiocarcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE The rhizomes of Dioscorea membrancea Pierre have been used in Thai traditional medicine as an ingredient formula for liver cancer and cholangiocarcinoma treatment. AIM OF THE STUDY To investigate the cytotoxic activity of ethanolic extract and constituents of D. membrancea to support its traditional use. MATERIALS AND METHODS The SRB assay was used to determine the cytotoxic activity against hepatocellular carcinoma (HepG2), cholangiocarcinoma (KKU-M156) cells and one normal human keratinocyte immortal cells (HaCaT) with its ethanolic extract and isolated compounds. Bioassay guided isolation was used for isolating cytotoxic compounds. RESULTS The ethanolic extract of D. membranacea rhizome showed weak cytotoxic against KKU-M156 and HepG2 (IC50 at 72h exposure=30.49±0.82 and 38.97±2.04µg/mL respectively). A new steroid [epipanthogenin B (1)], a known steroid [panthogenin B (2)], two napthofuranoxepins [dioscorealide A (3) and dioscorealide B (4)], phenanthraquinone [dioscoreanone (5)] and two phenanthrene [5,6-dihydroxy-2,4-dimethoxy-9,10-dihydrophenanthrene (6) and 2,5,6-trihydroxy-3,4-dimethoxy, 9, 10-dihydrophenanthrene (7)] were isolated from active chloroform fraction. Compound 4 showed the highest cytotoxicity against HepG2 (IC50 at 72h exposure=2.87±0.21µM) and KKU-M156 (IC50 at 72h exposure=1.67±0.10µM) and less toxicity against normal cell line (HaCaT) (IC50 at 72h exposure>100µM). Compound 5 showed selective cytotoxic activity against KKU-M156 (IC50 at 72h exposure=3.46±0.11µM). Compounds 6 and 7 showed weak cytotoxic activity against HepG2 (IC50 at 72h exposure=24.96±2.32 and 51.31±3.52µM). Compounds (1-3) showed no cytotoxic activity against HepG2 and KKU-M156 cell lines (IC50 at 72 h exposure>100µM). CONCLUSION Seven compounds were isolated from active chloroform fraction of the ethanolic extract of D. membranacea rhizomes. Only dioscorealide B (4) might be served as a good anticancer agent for liver cancer and cholangiocarcinoma cancer because it can kill cancer cell but not toxic on normal cell. This research support Thai traditional medicine use of D. membranacea for liver cancer and cholangiocarcinoma cancer treatment.