Chemical analysis of raw, dry-roasted, and honey-roasted licorice by capillary electrophoresis.

In herbal medicine, licorice is usually processed using a roasting procedure which might modify the chemical compositions in licorice. To test this hypothesis, licorice root samples were roasted under various conditions (with or without honey) and subsequently extracted by refluxing with 95% ethanol. The analysis of chemical compositions of licorice root extracts was achieved by capillary electrophoresis. The running buffer has been optimized to be 50 mM sodium tetraborate (pH 9.01) containing 5 mM beta-cyclodextrin. Thermal decomposition of glycyrrhizin, which was a major ingredient in licorice, was first studied in detail, indicating the conversion of glycyrrhizin to glycyrrhetinic acid. The licorice extracts were then analyzed to indicate the above thermal conversion did occur in the licorice samples. This finding may shed some light on understanding the differences in the therapeutic values of raw versus roasted licorice in herbal medicine.