Assessment of free, esterified, and insoluble-bound phenolics of green and red perilla leaves and changes during simulated gastrointestinal digestion

Soluble (free, esterified) and insoluble-bound phenolics and changes in the bioactive compounds and antioxidant activities during simulated digestion of raw green and red (Perilla frutescens) leaves were determined in this study. HPLC analysis revealed that the predominant phenolic compounds were rosmarinic acid (RA) in the free fraction and caffeic acid (CA) in the insoluble-bound fraction. Interestingly, in the free phenolic extraction, green perilla had higher RA, whereas red perilla exhibited higher levels of esterified and insoluble-bound phenolics. Simulated digestion illuminated a continuous increase in antioxidant content and activity during the transition from the stomach to the small intestine. After the gastric phase, the release of total bioactive compounds and antioxidant activity increased under alkaline conditions in the small intestine, with red perilla releasing more than green perilla. These findings provide a clearer understanding of the health benefits of polyphenols in Japanese perilla leaves and provide a scientific basis for the potential health benefits of adding nutrients to foods.