Impact of In Vitro Gastrointestinal Digestion on Polyphenolic, Anthocyanin Content, and Antioxidant Activity of Berries and Their Extracts

Anthocyanins are notable polyphenols with extensive health benefits primarily found in red and purple plant foods. However, the low bioavailability of these phytonutrients has been a challenge that may hinder their beneficial effects. Therefore, concentrated forms of these compounds in the form of extracts have become prominent as dietary supplements or nutraceuticals. Whether these products are superior to the consumption of whole foods rich in anthocyanins in terms of bioavailability remains unclear. The aim of the present study is to investigate the changes in polyphenol content, anthocyanin content, and antioxidant activity of acai berry and blueberry during the in vitro gastrointestinal digestion stages following the INFOGEST protocol. Freeze-dried powder was utilized to represent whole foods and compared to their corresponding extracts prepared in laboratory conditions, representing concentrated dietary supplements. Polyphenol content, anthocyanin content, and antioxidant activity were measured at different stages of digestion (oral, gastric, and intestine for powders; gastric and intestine for extracts). Data were analysed to determine significant differences between the powders and extracts using two-way ANOVA. The results showed no significant differences in polyphenol and anthocyanin content between forms (powder and extract) for both acai and blueberry (p>0.05). For antioxidant activity, significantly higher antioxidant levels were observed in extracts (gastric: 22.7±6.6 and intestine: 11.3±2.7 nmole/μL, Trolox equivalents) compared to powders (gastric: 16.2±4.7 and intestine: 9±1.3 nmole/μL, Trolox equivalents). Acai berry consistently showed higher polyphenol and anthocyanin contents, as well as antioxidant activity compared to blueberry. In addition to this, polyphenol content and antioxidant activity were significantly reduced after each digestive stage whereas no significant changes were observed in anthocyanin content.