Extraction of nutraceutical compounds from licorice roots with subcritical water

Subcritical water (SBW) extraction of licorice root (LR) was carried out at four different temperatures (50, 100, 200, and 300 °C) for 10, 30, or 60 min, and nutraceutical compound levels of the SBW extracts were evaluated. SBW treatment of LR increased the antioxidant activity of extracts. Higher radical scavenging activity, reducing power, and total phenol content of the LR extracts were found when SBW extraction was carried at 200 °C for 60 min or at 300 °C for more than 30 min. The main active compounds such as glycyrrhetic acid (GA) and glycyrrhizin (GL) showed different extraction patterns. GA and GL were present at maximum levels following SBW extraction at 100 °C for 30 and 60 min, respectively. However, liquiritin (LQ), another nutraceutical compound of LR, showed the highest levels following extraction at 300 °C for 60 min. The results indicated that the temperature and time of SBW extraction significantly affected the antioxidant activities and nutraceutical compound levels of LR extracts.