title: Isolation and characterization of a new cytotoxic dihydrophenanthrene from Dioscorea membranacea rhizomes and its activity against five human cancer cell lines.
abstract: BACKGROUND
  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.
  
  
  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).
  
  
  CONCLUSIONS
  The phytochemicals isolated from DM may serve as lead compounds for the design of new anti-cancer agents with better selective cytotoxic indices.
authors.affiliation: Department of Applied Thai Traditional Medicine, Faculty of Medicine, Thammasat University, Klongluang, Pathumthani 12120, Thailand; Center of Excellence on Applied Thai Traditional Medicine Research (CEATMR), Thammasat University, Pathumthani 12120, Thailand. Electronic address: iarunporn@yahoo.com.
authors.forename: Arunporn
authors.initials: A
authors.lastname: Itharat
authors.affiliation: Ph.D Program on Medical Science (Nutraceuticals), Graduate School, Faculty of Medicine, Thammasat University, Klongluang, Pathumthani 12120, Thailand.
authors.forename: Pakakrong
authors.initials: P
authors.lastname: Thongdeeying
authors.affiliation: Department of Applied Thai Traditional Medicine, Faculty of Medicine, Thammasat University, Klongluang, Pathumthani 12120, Thailand; Center of Excellence on Applied Thai Traditional Medicine Research (CEATMR), Thammasat University, Pathumthani 12120, Thailand.
authors.forename: Srisopa
authors.initials: S
authors.lastname: Ruangnoo
mesh_terms: D045744:Cell Line, Tumor; D027742:Dioscorea; D006801:Humans; D008518:Medicine, East Asian Traditional; D008519:Medicine, Traditional; D010616:Phenanthrenes / Q000737:chemistry* / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology*; D027343:Rhizome; D013785:Thailand
chemical_list: D010616:Phenanthrenes; D010936:Plant Extracts
keywords: Cytotoxicity test; Dihydrophenanthrenes; Dioscorea membranacea; SRB assay