Butenylbithiophene, alpha-terthienyl and hydroxytremetone as contact allergens in cultivars of marigold (Tagetes sp.).

Ornamental cultivars of Tagetes sp., commonly named marigold, are one of the presently most popular pot and garden plants. Sensitizing experiments in guinea pigs with short ether extracts and isolated compounds revealed the presence of 3 constituents that must be considered as contact allergens. They were identified as 5-(3-buten-1-ynyl)-2,2'-bithiophene, alpha-terthienyl and hydroxytremetone. In sensitized animals, butenylbithiophene showed moderate to strong sensitizing potency, while alpha-terthienyl was less strong and hydroxytremetone weak. The results demonstrate, for the first time, that at least some of the thiophenes abundantly occurring in many species of the Compositae family possess not only phototoxic activity but also sensitizing properties.