Bioaccessibility of Apple Polyphenols from Peel and Flesh during Oral Digestion

Health benefits of apple polyphenols for different chronic diseases are postulated. To exert bioactive properties,absorption into the body is required (bioavailability), which is strongly influenced by matrix release (bioaccessibility). For sevenapple varieties, in vitro experiments with simulated salivafluid (SSF) and ex vivo digestion with centrifuged human saliva wereconducted. Polyphenol characterization (high-performance liquid chromatography-tandem mass spectrometry) and quantification(high performance liquid chromatography-diode array detection) was related to an aqueous methanolic extraction. A polyphenolrelease of 63-82% fromflesh and 42-58% from peel was estimated. While hydroxycinnamic acid derivatives were released in total, asignificant retention was observed forflavanes andflavones. In particular, procyanidins were retained with increasing molecularweight. The data reveal a considerable polyphenol release during the oral digestion; however, differences among the varieties as wellasflesh and peel were obvious. Due to negligible differences between both digestion media, the data supported the use of SSFinstead of human saliva in further experiments