DETERMINATION OF URUSHIOL IN ALLERGENIC EXTRACTS--URUSHIOL STABILITY

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The active constituents in allergenic extracts of Poison Ivy and other plants of the genus toxicodendron have been generically designated as "urushiol", a mixture of penta- or heptadecenyl catechols. Extracts currently available for oral administration or injection are formulated in plant oils, e.g. almond, corn or olive oil. Urushiol compounds may oxidize to orthoquinones which are capable of undergoing Michael-addition reactions with nucleophilic compounds. Olefinic sites on other urushiol molecules may function as nucleophiles, resulting in oligomerization of urushiols present in solution. Objectives of this project are: a) to develop methods for the quantitative analysis of urushiol, including speciation of individual compounds; b) to develop sample preparation techniques to isolate urushiol from plant oil matrices; c) to develop methodologies to determine oxidized and oligomerized urushiol degradation products; d) to correlate urushiol degradation with factors of concentration, solution type and storage conditions. Urushiol samples have been speciated and quantitated by gas chromatography of trimethylsilyl derivatives using a polar stationary phase, OV-225. Validation studies have been performed for this method. A normal phase HPLC method utilizing a silica column is to be investigated as well as a capillary gas chromatographic procedure that would provide better resolution of individual compounds. Procedures for the isolation of urushiol at high (greater than 100 microg/ml) concentrations from plant oils have been validated, development of a solid phase extraction procedure for isolation of urushiol at low (less than 10 microg/ml) concentrations is in progress. Initial studies involving speciation of urushiol oligomers by gel permeation chromatography have been performed.