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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. [ABSTRACT FROM AUTHOR]

Australian Blackwood is known to be an important cause of allergic contact dermatitis in Australia. Previous investigations have shown that 2,6-dimethoxy-1,4-benzoquinone and acamelin are 2 of the responsible, but weak, sensitizers. When these 2 quinones are lacking, which is occasionally found, the wood still possesses allergenic properties. The present re-examination led to the isolation and identification of 4 hydroxyflavans, of which 3 proved to be allergens. Melacacidin, known to be the main constituent of these flavan derivatives in the heartwood, was isolated and its sensitizing capacity in guinea pigs determined. It showed a moderate sensitizing power. Melacacidin occurs abundantly in 125 Australian and 3 African Acacia species. [ABSTRACT FROM AUTHOR]

Experimental and chemical investigations revealed that common ivy (Hedera helix susp. helix) contains 3 compounds which are powerful irritants and moderate sensitizers. Only 2 of these constituents, falcarinol and didehydrofalcarinol, are present in the plant during the whole year. Besides Panax ginseng and Srchfflera arboricala, this is the third species of the Araliaceae in which these polyacetylenic sensitizers have been found. Falcarinol and didehydrofalcarinol also occur in Hedera helix subsp canariensis, 4 patients have been patch tested. Even in low concentrations (0.03%). the main allergin falcarinol elicited strong reactions in all of them. One of the authors became sensitized during the investigations. [ABSTRACT FROM AUTHOR]