Comparative Study of Total Polyphenol Content and Antioxidant Activity of Yomogi Tea and Green Tea during Simulated In Vitro Gastrointestinal Digestion

This study explores the total polyphenol content (TPC), antioxidant activity (DPPH and ferric reducing antioxidant power (FRAP)), and color differences of green tea and yomogi tea, with a focus on TPC, DPPH, and FRAP after in vitro digestion. Methanol and hot water extractions were applied to leaf and powder forms of the teas. The methanol extraction method demonstrated greater efficiency compared to hot water extraction, particularly in powdered tea. Green tea exhibited higher TPC (105 mg GAE/g dry matter) and antioxidant activity (DPPH: 301 μmol TE/g dry matter; FRAP: 307 mmol FeSO4/g dry matter) than yomogi tea (TPC: 103 mg GAE/g dry matter; DPPH: 236 μmol TE/g dry matter; FRAP: 272 mmol FeSO4/g dry matter). After digestion, both teas retained significant antioxidant activity with green tea maintaining higher DPPH and FRAP values. The TPC increased during digestion for both teas, with green tea showing a 20.0% increase and yomogi tea showing a 60.3% increase. Both green tea and yomogi tea demonstrated good stability under digestive conditions, highlighting the importance of digestive stability on the bioactive properties of teas. These findings indicate that both teas have significant potential as functional ingredients.