New hydroxyisoflavans as contact sensitizers in cocus wood Brya ebenus DC (Fabaceae)

A 15-year-old girl developed perioral dermatitis and swelling of the lips, having played a flute made of cocus wood for 2 years. Patch tests with wood shavings, as well as with subsequently isolated constituents named Cocus I and Cocus II, were strongly positive. After complete purification, both contact allergens were identified as isoflavan derivatives. While Cocus I was shown to be 7,8-dihydroxy-2',4',5'-trimethoxyisoflavan, the structure of Cocus II could not be elucidated exactly. It could have been either 7,8,3'-trihydroxy-2',4'-dimethoxyisoflavan or 7,8,2'-trihydroxy-3',4'-dimethoxyflavan. The exact position of the hydroxy and methoxy group in C-2' and C-3' can be determined only by complete synthesis of both compounds or by isolation of greater amounts of Cocus II for further oxidation experiments. Due to the stronger patch test reaction and the higher yield of Cocus I in the wood, this hydroxyisoflavan must be recognized as the main contact allergen.