Effect of exogenous melatonin on the isoflavone content and antioxidant properties of soybean sprouts

Sprouting can increase the nutritional quality of seeds, such as soybeans. The current study aimed to evaluate the influence of exogenous melatonin (MLT; 100 and 300 μmol/L) on the isoflavone content and antioxidant properties of two soybean cultivars’ germination process (5, 6, and 7 days). MLT treatments significantly increased the sprout length and germination rate by 53% and 12%, respectively, when compared to water-treated soybean sprouts. Further, seven main isoflavones were quantified, with the highest total isoflavone content (5.101 g/kg) found on day 5 when using 100 μmol/L MLT. Additionally, when applying the same concentration, the highest levels of SOD and CAT were found, with values of 10.05 and 15.10 μkat/g, respectively, therefore resulting in a decrease in malondialdehyde (MDA), hydrogen peroxide (H2O2), and nitric oxide (NO) contents. MLT enhanced the expression levels of several genes related to antioxidant properties, seed germination, and root length. Overall, MLT is a suitable inducer for promoting soybean germination and enhancing the isoflavone content and antioxidant properties of soybean sprouts.