Analysis of gamma irradiated pepper constituents, 4

A separation method for piperine and its isomers (isopiperine, isochavicine and chavicine) was investigated. These isomers were produced from piperine with irradiation. This reaction is photochemical isomerization. Piperine and its isomers were separated on a reversed phase C8 (LiChrospher 300 RP-8 10 um 0.4 I.D. x 0.4 cm and LiChrosorb RP-8 SelectB 0.4 I.D. x 25 cm) column with a mixture of 0.1% trifluoro acetic acid (TFA) in water and 75% acetonitrile-0.1% TFA in water (92 : 8) and detected at 210 nm, 280 nm. By this method, 4peaks which is originated piperine and its 3 kinds of isomers were possible to recognize. Piperine was identified by addition of piperine as a internal standard. And unknown peaks were fractionated by chromatography on the column for NMR structural identification. Isochavicine was identified by NMR. And the other peaks were presumed by the fact that chavicine dose not produce from piperine with mild irradiation condition. In contrast of photochemical isomerization, the effect of gamma irradiation on isomerization of piperine was investigated by HPLC analysis. Gamma irradiation had no effect on the isomerization of piperine. (author)