Effects of Drought Stress on the Quality of Licorice

Objectives: To establish a method to improve the quality of cultivated licorice by environmental stress. Materials and Methods: The fresh roots of Glycyrrhiza uralensis were soaked in 5%, 10%, and 20% polyethylene glycol‑6000 (PEG) for 4 days to construct a physiological state of drought. The changes in hydrogen peroxide (H2O2) and enzymes related to secondary metabolism in the treated licorice were observed, and their detoxication and anti‑oxidation were verified by reducing aconite‑induced cardiotoxicity and free radical scavenging rate experiments. Results: The H2O2 content notably boosted, and gene expression and allosterism of enzymes related to secondary metabolism such as 3‑hydroxy‑3‑methyl‑glutaryl‑coenzyme A reductase (HMGR), squalene synthase (SQS), β‑amyrin synthase (β‑AS), and phenylalanine ammonia‑lyase (PAL) were promoted, and enhance their activities. Under a drought stress of 10% PEG, secondary metabolites significantly increased, and the effectiveness of the drug also intensified. For the myocardial injury caused by aconite, compared with the untreated, creatine kinase (CK), cardiac troponin‑T (cTn‑T), and lactate dehydrogenase (LDH) decreased by 9.3%, 14.6%, and 6.3% in the 10% PEG. Meanwhile, the clearance rates of 1,1‑diphenyl‑2‑picryl hydrazyl radical (DPPH·) and hydroxyl radical (OH·) heightened by 7.5% and 13.1%, separately. Conclusion: Drought stress can greatly increase the secondary metabolites of licorice and enhance its detoxication and anti‑oxidation.