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.