In Vitro Digestibility of Enzymatically Synthesized Phenolic Glycosides with Different Glycosidic Linkage

Phenolic compounds exhibit important biological properties; however, their solubility affects bioavailability when they are consumed by oral administration. Enzymatic glycosylation of these molecules improves solubility and bioavailability; however, their stability under gastrointestinal conditions must be considered for functional food applications. In this study, the digestive stability of phlorizin, phloretin, and their enzymatically synthesized glycosides—phlorizin-4-O-monofructofuranoside (4PMF) and phloretin 4′-O-α-D-glucopyranoside—was evaluated using a static in vitro digestion model, simulating stomach and small intestine conditions (SC and SIC respectively). 4PMF showed high susceptibility to hydrolysis under SC and SIC (58 ± 2% and 99.5 ± 0.9%, respectively), whereas phloretin 4′-O-α-D-glucopyranoside exhibited significantly greater stability (5.7 ± 0.6% and 14 ± 1%, respectively). Statistical analysis confirmed significant differences between compounds and digestion phases (p < 0.05). Additional analysis revealed that β-fructosyl bonds are acid-labile, whereas α-O-glucosidic bonds are resistant to acidic conditions. Residual glycosidase activities were observed in the commercial digestive enzymes used under SC and SIC. These findings support a dual mechanism that affects the stability of phenolic glycosides during in vitro digestion under SC and SIC, with glycosidic bond type also playing a role.