Unraveling molecular mechanisms of 1-deoxynojirimycin and polyphenol biosynthesis in mulberry leaves in response to ultrasound elicitation: An integrated metabolomics and transcriptomics approach.

1-Deoxynojirimycin (1-DNJ) and polyphenols are the primary anti-diabetic components in mulberry leaves (MLs) but their low natural abundance limits their application. To address this, we investigated the impact of ultrasonication (US) on the accumulation of 1-DNJ, total phenolic content (TPC), and total flavonoid content (TFC) in MLs. Under the optimal conditions determined by the Box-Behnken design, 1-DNJ, TPC, and TFC levels increased by 2.10-, 2.66-, and 2.11-fold, respectively. US treatment also changed the surface microstructure and increased electrical conductivity, polyphenolic content, antioxidant capacity, as well as α-glucosidase, α-amylase, and xanthine oxidase inhibitory activities, while inhibiting polyphenol oxidase and peroxidase activities in MLs. Metabolomics and transcriptomics analyses identified 458 differential metabolites (DMs) and 9429 differentially expressed genes (DEGs). These DMs and DEGs are involved in key metabolic pathways for synthesizing 1-DNJ and phenolic compounds. Our findings demonstrated that US treatment boosted the biosynthesis of 1-DNJ and phenolic compounds by upregulating the expression of key enzymes, thereby increasing their contents in MLs. This study demonstrates an innovative strategy for improving bioactive components, particularly 1-DNJ, in MLs, providing the potential to increase the values of MLs in the food and nutraceutical industries.