Occupational airborne contact dermatitis from Machaerium scleroxylon: a simple method for extracting quinones from wood

Machaerion (M). scleroxylon is a tropical hardwood imported from South American of the Leguminosae family; it resembles Brazilian rosewood (Dalbergia) in appearance and strength. For these reasons it is used as a substitute for the Dalbergia species, although it can cause both irritant and allergic contact dermatitis mainly in woodworkers through airborne exposure. The main sensitizer is (R)-3,4-dimethoxydalbergione, a quinone with oxidative and entirely reduced states; the latter state is hydrosoluble and therefore by using the ultrasound method quinones can be extracted in an aqueous vehicle. Its main allergen is (R)-3,4-dimethoxydalbergione, which is the most sensitizing of the quinones or dalbergiones. The case of a 25 year old atopic man with itchy eczematous dermatitis of face, antecubital and popliteal folds, and thighs is reported. The patient, employed as a joiner in a small wood factory and assigned to the manufacture of parquet tablets, referred that his dermatitis healed when he took a break from his job but recurred when he resumed work. The skin lesions relapsed when he cut M. scleroxylon wood or when the patient worked in an environment that contained this wood dust. Gas-chromatography in solid-phase microextraction/GC/MS configuration on watery extracts of M. scleroxylon fresh sawdust showed the presence of several chemicals from the quinine family and a large amount of styrene. This compound is usually painted on the wood surface to improve its acoustic property. Patch and prick testing showed positive eczematous reactions to M. scleroxylon ethanolic and aqueous extracts. These last extracts were obtained using the ‘ultrasonic bath’ method. This method is quicker and less expensive than ethanolic extractive techniques. Therefore, the ultrasound method could be a valid alternative to study plant and wood hydro-soluble allergens. Moreover, the aqueous extracts cause less irritant effects than alcoholic extracts when these are patch tested.