Simultaneous Extraction and Depolymerization of Condensed Tannins from Chinese Bayberry Leaves for Improved Bioavailability and Antioxidant Activity

Biorefineries of polyphenols from plant leaves maximize their commercial value for developing biomedicines and nutrients. However, condensed tannins (CTs) constitute extensive polyphenols from plant leaves, which hinders the maximization due to extremely low bioavailability. Therefore, a simple, and sustainable one-step method was established to simultaneously extract polyphenols and depolymerize CTs with only endogenous flavan-3-ols from Chinese bayberry leaves via acid catalysis, which markedly improved the bioavailability of total polyphenols. Afterward, purification of polyphenols from depolymerized extract was studied with specific polymeric resins. Silica C18 showed the highest absorption efficiency of total polyphenols, while Amberlite XAD-7 and XAD-2 presented high selectivity toward polyphenols with high and low molecular weight, respectively. Combined depolymerization of CTs and purification with Amberlite XAD-2 showed the highest bioavailability and cellular free-radical scavenging activity of total polyphenols, which proved to be an ideal methodology for improving the bioavailability and activity of polyphenols from plant leaves.