Evaluation of the antidiabetic potential and bioaccessibility of propolis-enriched aronia kombucha: an in vitro study

Defined as a fermented tea beverage, kombucha is obtained via the metabolic activity of a symbiotic culture of bacteria and yeasts (SCOBY) in sweetened tea, and it is widely recognized for its associated functional and bioactive properties. In this study, kombucha fermented with aronia tea (AK) and aronia kombucha enriched with propolis (PAK) were examined together to evaluate bioactive components, phenolic profile, in vitro bioaccessibility, and antidiabetic potential. Response surface methodology showed that the amount of aronia tea (X 1 ) and the concentration of propolis (X 2 ) had significant effects on TPC, TFC, and DPPH; the optimum formulation was obtained at a level of 11.09 g/L aronia tea and 1.42% propolis. Throughout the fermentation, PAK exhibited higher values for TPC compared to AK; TPC, which was 367.32 ± 2.56 μg GAE/mL on day 0, was maintained at 345.28 ± 4.40 μg GAE/mL on day 14. Although TPC/TFC decreased in both groups during simulated digestion, PAK maintained a higher level in all phases; recovery was found to be ~34% in TPC and ~40% in TFC. In the phenolic profile, rutin (1.18 → 3.03 μg/mL) and t-ferulic acid (0.66 → 2.21 μg/mL) increased with fermentation, while the addition of propolis significantly enriched flavonoids, especially chrysin (≈17.75–19.14 μg/mL) and quercetin (day 14: 1.55 μg/mL). This phenolic potentiation is consistent with PAK enhancing α -glucosidase (42.04%) and α-amylase (44.68%) inhibition. Future studies should investigate reproducibility, colonic fermentation-microbiota interaction, and target metabolite tracking under varying sucrose levels and SCOBY profiles; clinical validation should also be supported by sensory acceptance, shelf life, and safety parameters.