title: Antitumor effects of curcin from seeds of Jatropha curcas.
abstract: OBJECTIVE
  To study the antitumor effects of curcin from Jatropha curcas.
  
  
  METHODS
  Antitumor activity of curcin was tested by MTT assay. The N-glycosidase activity of curcin was determined by characterization of R-fragment in gel. A cell-free system, rabbit reticulocyte lysate, was introduced to quantify the inhibitory activity of curcin on protein biosynthesis.
  
  
  RESULTS
  The curcin had a powerful inhibitory action upon protein synthesis in reticulocyte lysate with an IC50 (95 % confidence limits) value of 0.19 (0.11-0.27) nmol/L. The IC50 (95 % confidence limits) of curcin on SGC-7901, Sp2/0, and human hepatoma was 0.23 (0.15-0.32) mg/L, 0.66 (0.35-0.97) mg/L, 3.16 (2.74-3.58) mg/L, respectively. Curcin was found to have no toxic to Hela cells and normal cells (MRC). After the rRNA of ribosome was treated with curcin and aniline at acidic condition, a cleaved R-fragment of approximately 450 nt appeared, but this fragment did not occur after treatment with curcin only. A comparison of the amino acid sequences of curcin, ricin A-chain and trichosanthin revealed that there were relatively high similarities among them. The percentages of homology between curcin and ricin A chain, between curcin and trichosanthin were found to be 54 % and 57 % respectively. Especially, the conserved residues forming the active sites of the A chain of ricin and trichosanthin occurred in curcin.
  
  
  CONCLUSIONS
  Curcin has an obvious antitumor effect and its mechanisms are related to the N-glycosidase activity.
authors.affiliation: College of Life Science, Sichuan University, Chengdu 610064, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Lin
authors.forename: Fang
authors.initials: F
authors.lastname: Yan
authors.forename: Lin
authors.initials: L
authors.lastname: Tang
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000302:isolation & purification / Q000494:pharmacology*; D006801:Humans; D031286:Jatropha / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology*; D010946:Plants, Medicinal / Q000737:chemistry; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012335:RNA, Ribosomal / Q000032:analysis; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D054788:Ribosome Inactivating Proteins; D012276:Ricin / Q000235:genetics; D012639:Seeds / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015978:Trichosanthin / Q000235:genetics; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; D012335:RNA, Ribosomal; D015978:Trichosanthin; D012276:Ricin; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins