A new tumor promoter from the seed oil of Jatropha curcas L., an intramolecular diester of 12-deoxy-16-hydroxyphorbol.

A new type of phorbol ester, which has a macrocyclic dicarboxylic acid diester structure, was isolated from the seed oil of Jatropha curcas L. (Euphorbiaceae). Based on the results of spectroscopic analyses of the compound and its chemical degradation products, its structure is proposed to be an intramolecular 13,16-diester of 12-deoxy-16-hydroxyphorbol, 12-deoxy-16-hydroxyphorbol-4'-[12',14'-butadienyl]-6'-[16',18',20' - nonatrienyl]-bicyclo[3.1.0]hexane-(13-O)-2'-[carboxylate]-(16-O)-3 '- [8'-butenoic-10']ate (DHPB). DHPB showed slightly weaker biological and biochemical activities than 12-O-tetradecanoylphorbol-13-acetate (TPA). DHPB induced ornithine decarboxylase in mouse skin (2.8 nmol CO2/30 min/mg protein/34 nmol application), inhibited the specific binding of [3H]-12-O-tetradecanoylphorbol-13-acetate to phorbol ester receptors (50% effective dose, 17.0 nM), and activated protein kinase C in vitro (50% effective dose, 36.0 nM). Also, a weak tumor-promoting activity of DHPB was found in a two-stage carcinogenesis experiment on mouse skin. One week after initiation of mice with 100 micrograms of 7,12-dimethyl-benz(a)anthracene, topical application, twice a week, of 2 micrograms of DHPB until week 17, followed by application of 5 microgram of DHPB until week 30 at the same rate, resulted in 46.7% incidence of tumors by week 30. The groups treated with 7,12-dimethylbenz(a)anthracene alone or DHPB alone did not produce significant numbers of tumors. These results indicate that the new phorbol ester, DHPB, is a tumor promoter with weaker activity than 12-O-tetradecanoylphorbol-13-acetate.

Presence of tumor promoters in the seed oil of Jatropha curcas L. from Thailand.

The seed oil of Jatropha curcas L. was shown to contain skin tumor promoters in a two-stage mouse carcinogenesis experiment. By using the irritant test on mouse ear to monitor activity, the "irritant fraction" was partially purified from the methanol extract of the seed oil by column chromatographies on Florisil and Sephadex LH-20. The irritant fraction obtained induced ornithine decarboxylase in mouse skin and inhibited the specific binding of 3H-12-O-tetradecanoylphorbol-13-acetate to a particulate fraction of mouse skin. After initiation with 7,12-dimethylbenz[a]anthracene (DMBA), this "irritant fraction" induced tumors in the skin of 36% of the mice tested in 30 weeks. Tumor incidences in the groups treated with DMBA alone and "irritant fraction" alone were 7% and 13% in week 30, respectively. Since the skin of Thai people comes into direct contact with this seed oil, an epidemiological study on human skin cancer in Thailand is indicated.