Determination of the total phenolic content of commercially available green teas using an in vitro gastrointestinal system: a preliminary study

This preliminary study evaluated changes in total phenolic content and catechin and epicatechin levels in commercially available green teas through an in vitro digestion. Samples (1.5% dry tea in 100 mL water at 80°C) were analyzed for total soluble solids, pH, and color. The initial total phenolic content ranged from 381.19–1779.50 µg gallic acid equivalent/mL, decreasing to 315.22–1266.37 µg/mL in the small intestine. Epicatechin decreased from 7.64–13.97 µg/mL to 4.53–9.19 µg/mL, while catechin dropped from 13.13–24.03 µg/mL to 5.43–14.03 µg/mL. Significant decreases occurred across digestion, indicating reduced bioaccessibility of green tea polyphenols that may influence antioxidant and health effects.