Enhancement of bioaccessibility and modulation of green tea phenolic compounds through pre-transformation by Lactobacillus and Bifidobacterium strains

Green tea (Camellia sinensis L.) phenolic compounds are recognized for their antioxidant, anti-inflammatory, cardiometabolic, neuroprotective, and antidiabetic effect, however, their low bioaccessibility and structural instability in the gastrointestinal tract limit their helath-promoting bioefficacy. This study aimed to determine the influence of Lactobacillus and Bifidobacterium strains on the transformation and bioaccessibility of green tea phenolic compounds in a novel synbiotic system during in vitro digestion. Green tea extract (GTE) was combined with bacterial strains and subjected to digestion model incorporating real food matrix components (dietary fiber, oat flakes, flaxseed). Ultraperformance liquid chromatography coupled with mass spectrometry (UPLC-PDA-QTOF-ESI-MS) profiling was used to track the structural transformation and metabolic fate of flavan-3-ols, flavonols, and phenolic acids, assessing bacterial biotransformation and bioaccessible metabolite recovery. Bacterial metabolism significantly modulated flavan-3-ol stability, increasing intestinal bioaccessibility of (+)-catechin by 20-fold (79 %) while promoting the degradation of epigallocatechin gallate (EGCG), theasinensin A/D, and procyanidins B2 and B4 into bioactive derivatives. Bifidobacterium strains selectively enhanced the bioaccessibility of kaempferol aglycone and quercetin glucosides, with a synergistic protective effect observed in the presence of flaxseed. Caffeoylquinic acids and flavonols exhibited higher stability during gastric and intestinal digestion than galloylated catechins, suggesting distinct metabolic pathway. This study provides new evidence of bacterial-driven biotransformation of green tea phenolic compounds, offering an innovative strategy to improve dietary polyphenol bioaccessibility and bioefficacy. The findings highlight the potential for developing synbiotic functional products-such as fermented plant-based beverages, fiber-enriched snacks, or dietary supplements designed to deliver microbiota-transformed green tea phenolics with improved small-intestinal bioaccessibility, supporting formulation that enhance phenolic uptake and optimize dietary interventions in metabolic nutrition.