Exogenous Melatonin Delays the Aging of Gastrodia After Harvest and Maintains Its Quality

Gastrodia elata is not only a traditional Chinese medicine but also a food raw material. Gastrodia is very perishable, and its effective constituents decrease significantly. N-Acetyl-5-methoxytryptamine (melatonin) is widely used in the preservation of various fruits and vegetables after harvest. In this study, the optimal melatonin treatment concentration and duration (0.2 mM MT immersed for 3 min) were determined to effectively delay the weight loss rate, decay rate, and disease severity index of Gastrodia. Immersion of Gastrodia tubers with 0.2 mM MT for 3 min could delay the degradation of gastrodin (GAS), 4-hydroxybenzyl alcohol (4-HBA), balisside A (PA), balisside B (PB), balisside C (PC), and Gastrodia polysaccharide (GEF) during storage. This method can inhibit hydrogen peroxide (H₂O₂), superoxide anion (O₂•^-), and malondialdehyde (MDA); improve the radical clearance of (O₂•^-, OH•, and DPPH) during storage; and enhance the activities of key enzymes in the ascorbic acid–glutathione (AsA-GSH) cycle, leading to improved regeneration of ascorbic acid (AsA) and glutathione (GSH). Melatonin treatment also increased the activities of antioxidant enzymes, such as catalase (CAT) and superoxide dismutase (SOD); decreased the activity of peroxidase (POD); and enhanced the scavenging ability of reactive oxygen species (ROS). In addition, exogenous melatonin treatment increased endogenous melatonin content, thereby regulating the aging process of Gastrodia.