Chemical profiling of composite prescription caraway and quantification of three pairs isomeric components in caraway administered rat plasma by tandem mass spectrometry.

Caraway, a well-known traditional Uyghur medicine, has been used to treat vitiligo for centuries. Its biological effects on melanin synthesis of caraway have been investigated. However, beyond psoralen and isopsoralen alone, no further chemical component of caraway has been revealed. In this study, ultra-high performance liquid chromatography coupled with hybrid quadrupole orbitrap mass spectrometry was employed to comprehensively characterize the chemical components present in caraway. Based on accurate mass measurements, key fragmental ions and comparison with reference standards, 75 chemical components were identified in caraway. Moreover, a tandem mass spectrometry method was developed and validated for quantitative analysis of three pairs isomeric components, namely psoralen/isopsoralen, bavachin/isobavachalcone and bavachromene/isobavachromene in rat plasma. Psoralen, isopsoralen, bavachin, and isobavachalcone showed linearity with concentration ranging of 1.0-500.0 ng/ml. The linear ranges for bavachromene and isobavachromene were 0.2-500.0 ng/ml. The accuracies were in ranges of 85%-115% with coefficient of variation errors of less than 15%. Furthermore, the method was applied to quantify the three pairs isomeric components in rats after oral administration of caraway.