Metabolomics reveals the differential regulatory mechanisms of quality and flavonoid biosynthetic pathways during the drying process of varieties licorice

Flavonoids are one of the major chemical components in licorice. However, during the drying process, their chemical stability, content, and biological activity can all change. Moreover, the impact of different varieties on these aspects is still not clear. This study employed hot air-drying technology at 45-65 °C to examine the effect of drying temperature on the drying flavonoids, total phenolics, and antioxidant activity and other quality aspects in <i>Glycyrrhiza uralensis</i> and <i>Glycyrrhiza inflata</i> from the Xinjiang Uygur Autonomous Region, China. Results showed that the optimal drying temperature was 60 °C, at which the total phenolic content of both varieties of licorice reached its peak, with <i>G. inflata</i> achieving 2.42 mg GAE/g and <i>G. uralensis</i> reaching 2.46 mg GAE/g. However, drying significantly reduced the antioxidant activity of licorice. Additionally, there were 24 differential flavonoid metabolites between the dried samples of <i>G. inflata</i> and <i>G. uralensis</i>, among which 19 were up-regulated and 5 were down-regulated. <i>G. uralensis</i> retained better overall quality than <i>G. inflata</i> after drying. These findings provide insights into flavonoid metabolite and antioxidant regulation under drying stress, and valuable information for primary processing in licorice-producing areas.