Antitumor effects of curcin from seeds of Jatropha curcas.
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.
Lin
Juan
J
College of Life Science, Sichuan University, Chengdu 610064, China.
Yan
Fang
F
Tang
Lin
L
Chen
Fang
F
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
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