A general approach to evaluate bioaccessibility and bioavailability of complex phenolic extracts from two by-products: Olive Pomace (pâté) and Pomegranate Peel

The growing interest in botanical-based food supplements and medical devices is encouraging the sustainable exploitation of agro-industrial by-products, such as the pitted olive pomace (pâté) [1] and pomegranate peel [2]. These matrices, rich in phenolic compounds with known antioxidant and antiinflammatory properties, may offer benefits against chronic diseases associated with oxidative stress and inflammatory bowel diseases [3]. The aim of the study is to explore more thoroughly the bioaccessibility and the bioavailability of the phenolic compounds present in different complex extracts through in vitro approaches. Extracts were obtained from pitted olive pomace using ethanolwater and from pomegranate peel applying two hot water extractions at pH 7.0 and 8.2, and were characterized by HPLC-DAD-MS. The pâté extract was particularly rich in hydroxytyrosol and verbascoside, while the pomegranate peel extracts were characterized by α- and β-punicalagins upon extraction at neutral pH, and their derivatives – gallic acid, ellagic acid, α- and β-punicalins – in the extracts obtained with NaHCO3 at 0.6%. To evaluate the potential bioaccessibility of these phytocomplexes, the extracts underwent a standardized in vitro digestion protocol (INFOGEST 2.0) [4], simulating oral, gastric, and intestinal phases. The digested samples were analyzed to assess the stability and qualitative-quantitative modifications of phenolic compounds during digestion. These data provide preliminary insights into the bioaccessibility of phenolic components in different extracts. Differentiated Caco-2 cell monolayers, grown on transwell filters [5], are used for the subsequent investigation of trans-epithelial transport and potential bioavailability of the extracts after INFOGEST. This approach allows the evaluation of the effective passage of phenolic compounds through the intestinal barrier and their stability after contact with the apical membrane, offering a deeper understanding of the bioavailability of complex phenolic extracts. Chemical profiles in both apical and basolateral compartments can provide information on the extent of phenolic compound transport and metabolic modifications during transepithelial passage. This comprehensive approach will help elucidate the bioaccessibility, bioavailability, and the potential health benefits of phenolic compounds derived from olive pomace and pomegranate peel extracts.