Enzymatic preparation of epigallocatechin gallate diglucoside and bioactivity assessment

Epigallocatechin gallate (EGCG), the predominant catechin in green tea, has limited application due to its poor water solubility and instability. To address these issues, this study utilized recombinant sucrose phosphorylase to catalyze the glucosylation of EGCG, successfully synthesizing (-)-epigallocatechin gallate 4',4″-O-α-D-diglucopyranoside (EGCG-2G). The process was optimized using response surface methodology, achieving a 97.46% conversion rate of EGCG. EGCG-2G was purified to ≥ 99% purity by semi-preparative liquid chromatography. It exhibited approximately 124-fold higher water solubility than EGCG and demonstrated significantly enhanced stability under thermal and acidic conditions (50 °C, pH = 5), with an 84.82% and 35.36% improvement over EGCG and commercial (-)-epigallocatechin-3-gallate-4'-O-α-D-glucoside (EGCG-1G), respectively. Furthermore, EGCG-2G displayed notable antioxidant, anti-inflammatory, and anti-melanogenic activities. It effectively scavenged intracellular and extracellular free radicals, reduced inflammatory cytokine levels, and inhibited melanin synthesis. Molecular docking and gene expression analyses suggested that its anti-melanogenic effect might be associated with the MC1R/cAMP/MITF signaling pathway.