Urushiol is an oily organic allergen found in plants of the family Anacardiaceae, especially Toxicodendron spp. The oxidation and polymerization of urushiol in the sap of plant forms a hard lacquer in the presence of moisture to produce one of the most famous Korean lacquerware inlaid with mother-of-pearl. On the other hand, sumac has been used as a curing agent or food in some American Indians and Asian countries. It is also famous as an indigenous ingredient for healthy food, Otdak in Korea. This is a chicken soup boiled with Sumac. However, it has a little bit of a kind of poison which makes you feel itchy. For some sensitive individuals, urushiol may cause an allergic skin rash known as urushiol-induced contact dermatitis. This study was carried out to determine urushiol content in several food. The full process of urushiol analysis consists of extraction, TMS-silylation, analysis and identification by GC/MS. In order for the required accuracy and precision to be attained, each steps has to be optimized. A 30 g sample of Rhus verniciflua Stokes extract was stirred with 400 ml of acetone for 1 hour and filtered. The filtrate was evaporated and dissolved with ca. 60 mL of n-hexan. The hexane layer was transferred into a separating funnel containing same amount of water. After shaking, the upper layer was concentrated to dryness and dissolved with acetonitrile for analysis. Silylation of urushiol was carried out with standard reagents and Rhus verniciflua Stokes extract. The reagent stock solution mixed with 100 µL Sylon BFT mixture (BSTFA：TMCS=99：1, v/v) and 50 µL pyridine was heated at 80°C for 30 min. Very polar stationary phases give excellent separation of urushiol derivatives. HP-FFAP (30m × 0.32mm I.D, 0.25μm film thickness) was used. Oven temperature was hold I min at 90°C and increased upto 240°C at 10°C/min and hold for 10min. The injector temperature was 230°C in split mode 10:1. Eight components was found in derivatives from Rhus verniciflua Stokes (RV) extract with three urushiol reagent C15:1, C15:2 and C15:3 peaks. The content of urushiol was 1.28-8.80 μg/mL in tea bag, 14.54-87.79 ug/mL in sumac slice and 3.97-13.22 ug/mL in fresh sprout. The good linearity, r&gt;0.9997 showed in the range of 1-100 ug/mL. LOD was 0.43-0.87 ug/mL and LOQ was 1.29-2.63 ug/mL.

Experiment for analysis of urushiol in sumac and several indigenous food in Korea

253rd National Meeting (2017)

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