Isolation and characterisation of urushiol components from the Australian native cashew (Semecarpus australiensis)

Native cashew (Semecarpus australiensis) is a well-known food source for aboriginal people of northeastern Queensland and the Northern Territory. It is also well known that contact with the seeds at a certain stage of growth can cause sever dermatitis in susceptible individuals. To prepare the fruits for eating, they are commonly treated by leaching for 2-7 days with water followed by heating in bark, and this treatment apparently produces an edible cashew nut. Recently, attempts have been made to use this valuable source of food by a commercial company. It was necessary to identify the active principle(s) in the seeds to determine the most effective way of rendering the seed suitable for human consumption without altering the flavour. By using solvent extraction and silica-gel chromatography, a fraction containing one major urushiol was obtained. Its structure was confirmed by comparison of its NMR and mass spectral (MS) data with that previously reported. This compound, which is found in high yield, is also found in poison ivy (Toxiodenron radicans) and is responsible for dermatitis in susceptible individuals. A method of removing the active principle from the seed has been suggested.