Polyphenol profile matters: complementary contribution of extractable and non-extractable polyphenols over metabolic...

By-products (BPs) from mango, roselle, pomegranate, and grape are rich in extractable (EPPs) and non-extractable polyphenols (NEPPs). These BPs were used to formulate three high-fiber blends (60-67 % dietary fiber) with distinct NEPP:EPP ratios: 55:45 (Blend 1), 67:33 (Blend 2), and 78:22 (Blend 3). A total of 77 EPPs, 9 organic acids, and 23 hydrolyzable polyphenols were identified using UPLC-ESI-QTOF-MSE. Supplementation with these blends in a high-fat, high fructose, and cholesterol diet demonstrated that rats fed blends 1 and 2 showed the greatest reduction in body weight gain (8.0 % and 7.8 %, respectively), along with significant decreases in the HOMA index (P < 0.05), with reductions of 40.4 % in both cases. Blend 2 significantly lowered serum triglycerides (-47.3 %), while blend 3 increased HDL cholesterol (+52.1 %). Twenty-two urinary metabolites were also identified, including urolithin A (blend 1), catechol sulphate and apigenin diglucuronide (blend 2), and (epi)-catechin glucuronide and hydroxyequol (blend 3). This indicated that the composition of the blends influenced polyphenol bioavailability and, consequently, their in vivo effects. Overall, blends with NEPP:EPP ratios of 55:45 and 67:33 provided greater improvements in lipid and carbohydrate metabolism compared with the 78:22 ratio. So, different mixing ratios of NEPP and EPP yield distinct health effects. Given the similar dietary fiber content across blends, differences in metabolic outcomes are likely related to divergent polyphenol profiles (EPP vs NEPP content and composition). However, other factors such as fiber source and fermentability may also have contributed and are acknowledged as limitations. Overall, these findings highlight the importance of balancing NEPP:EPP content in the design on functional ingredients.