Studies of aflatoxins in Chiang Mai, Thailand

Aflatoxins become an economical problem in our country due to its contamination in agricultural commodities for export. The toxin may also cause hepatoma and liver diseases in the Thais as well. It is, therefore, necessary to search for and to develop efficient technology to combat and control such dangerous mold and mycotoxins. This paper is a collection of our previous and present studies towards reduction of risk from aflatoxins in foods and feedstuffs. The investigation of mold and aflatoxin contamination in local foods and feedstuffs in Chiang Mai area was made. The inhibitory effect of garlic extract on growth of Aspergillus flavus and its aflatoxin production was demonstrated. Detoxification of aflatoxins by chemicals such as ammonium carbonate, ammonium bicarbonate and ammonium benzoate was also shown. Preventions of toxigenic mold growth and its aflatoxin production by means of some food preservative were reported. Modifications of such effective chemicals were investigated for safety in future application.

Composition of popular tobacco products in Thailand, and its relevance to disease prevention

BACKGROUND

This report presents new findings on the composition of the three best-selling brands of commercially produced Thai cigarettes, representing about 80% of market share in Thailand, and six best-selling tobacco products, including hand-rolled cigarettes and cigars.

RESULTS

With one exception, all Thai cigarettes yielded higher levels of tar and nicotine than U.S. brands sold in Thailand. High levels of tar, nicotine, and carbon monoxide (CO) were found in the smoke of popular Thai cigars (Khiyo) and Burmese cigars sold in Thailand. All tobacco products tested were ranked in order of smoke yields of tar (cigarettes, 4.5 to 40.8 mg/cigarette), nicotine (0.19 to 5.77 mg/cigarette), and CO (3.1 to 9.5 mg/cigarette). The labels "very strong," "strong," and "mild," used in rating the tobacco quality by the growers in Thailand, were not found to reflect the relative nicotine and tar yields. From 1985-1990, per capita consumption of cigarettes in Thailand increased 1.4-fold.

CONCLUSION

This report provides information that may prove helpful in the evaluation of the tar, nicotine, and carbon monoxide yields of cigarettes and cigars in Thailand compared with levels in U.S. cigarettes. It is our goal to offer the scientific basis for voluntary and/or regulated reduction of the smoke yields of tobacco products in Thailand.

Specific binding of okadaic acid, a new tumor promoter in mouse skin

The tumor promoter okadaic acid binds specifically to a particulate as well as a cytosolic fraction of various mouse tissues, e.g., skin, brain, lung and colon. The KD value was 21.7 nM for receptors in the particulate fraction and 1.0 nM for those in the cytosolic fraction of mouse skin. The specific binding of [3H]okadaic acid to the particulate fraction of mouse skin was inhibited dose-dependently by okadaic acid, but not okadaic acid tetramethyl ether, an inactive compound, or by other tumor promoters, such as 12-O-tetradecanoylphorbol-13-acetate and teleocidin. The results suggest a new pathway of tumor promotion mediated through the okadaic acid receptor(s).

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.