Bioavailability and gut microbiota modulation of polyphenol from Camellia oleifera shells during digestion and fermentation in vitro

Camellia oleifera shells (COS) are a by-product of camellia oil processing and are rich in polyphenols. To date, the polyphenols extracted from COS have not been fully developed. In this study, two polyphenol fractions, referred to as 20P and 40P, were obtained by sequentially eluting the COS crude extract from an AB-8 macroporous resin column using ethanol at concentrations of 20% and 40% with different polarities. In addition, the biotransformation processes of these two polyphenols and their effects on the gut microbiota were studied. The results of in vitro digestion showed that at the end of the intestinal digestion stage the total phenolic content (TPC) content (0.34 ± 0.050 mg gallic acid equivalent (GAE) mg-1 dry weight (DW)) and antioxidant activity (0.53 ± 0.0076 mg vitamin C (Vc) mg-1 DW) of the 20P component were significantly higher than those of the 40P component (0.19 ± 0.020 mg GAE mg-1 DW; 0.39 ± 0.016 mg Vc mg-1 DW). In addition, the experiment also found that the phenolic composition and transformation process of 20P and 40P components were significantly different, and the TPC content (0.30 ± 0.058 mg GAE mg-1 DW) and antioxidant capacity (0.73 ± 0.034 mg Vc mg-1 DW) of the 40P component were significantly higher than that of the 20P (0.13 ± 0.035 mg GAE mg-1 DW); (0.19 ± 0.013 mg Vc mg-1 DW) component during in vitro fermentation. This may be related to the types of compounds extracted by solvents with different polarities. In addition, both 20P and 40P components significantly regulated the gut microbiota and promoted the production of short-chain fatty acids. These results indicate that polyphenols from different polar sources of COS can serve as valuable bioactive compounds with potential health-regulating properties. © 2025 Society of Chemical Industry.