Comparison of chemical constituents among licorice, roasted licorice, and roasted licorice with honey

Misato Ota, Feng Xu, Yao-Li Li, Ming-Ying Shang, Toshiaki Makino, Shao-Qing Cai

Licorice (root and rhizome of Glycyrrhiza uralensis Fisch.) is sometimes used as crude drug after processing. In this report, we prepared roasted licorice with or without honey using 3 lots of crude drug samples derived from wild G. uralensis, and analyzed the constituents in unprocessed, roasted, and honey-roasted licorice samples by high performance liquid chromatography-electrospray ionization-ion trap-time of flight mass spectrometry (HPLC-ESI-IT-TOF-MS(n)) with principal component analysis. We found that the areas of 41 peaks were noticeably changed by processing. Among them, the areas of 12 peaks, viz. isoliquiritin, isoliquiritigenin, glucoisoliquiritin, 6″-O-acetylisoliquiritin, 6″-O-acetylisoliquiritin apioside, glycyrrhetinic acid 3-O-glucuronide, 5 kinds of sugar-derivatives and one compound whose molecular weight was 386 Da were increased by roasting in all 3 lots, and those peak areas were increased by higher heating temperatures. Among the increased peaks, 3 kinds of sugar-derivatives had larger areas, and 6″-O-acetylisoliquiritin had lower areas than those in honey-roasted licorice. Those sugar-derivatives were the only characteristics differing between honey-roasted licorice and roasted licorice. Meanwhile, the areas of 9 peaks, four of them identified as 6″-O-acetylliquiritin, 6″-O-acetylliquiritin apioside, formononetin and gancaonin L, were decreased by roasting in all 3 lots, but there were no differences between roasted licorice with or without honey. Those compounds whose amounts were changed by processing could be used as markers for the quality control of roasted and honey-roasted licorice.