Non-extractable phenolic compounds, the major macromolecular antioxidants, are polyphenols (from small phenolic acids to high molecular weight proanthocyanidins) linked to plant food macromolecules. They reach the colon intact, where they are transformed by the microbiota, releasing metabolites with beneficial effects either local and/or systemic after absorption. Despite the increasing evidence of the potential beneficial role of macromolecular antioxidants, studies on their presence in foodstuffs are still limited. During the last years, we have published data on the content of these compounds in several samples, such as the most consumed fruit and vegetables. In this study, we evaluated by the first time the non-extractable polyphenols content in peels from common fruits as well as in grape and pomegranate pomaces. After performing different hydrolysis procedures in order to release non-extractable phenolic compounds from the food matrix, the determination of their content was carried out by a combination of spectrophotometric and HPLC-MS techniques. Fruit peels presented appreciable contents of non-extractable phenolic compounds, from 700 mg/100 g dw in watermelon to 11,730 mg/100 g dw in banana. In the case of grape and pomegranate pomace, parallel hydrolysis procedures were used, allowing a more comprehensive release of non-extractable phenolic compounds. These results will be used as basis to discuss advantages and drawbacks of the current methodologies for the analysis of non-extractable phenolic compounds. In conclusion, increasing data show the quantitative and qualitative relevance of this fraction of dietary bioactive compounds, what urges to the establishment of standardized analytical methodologies for their determination.<br/>

Analysis of non-extractable phenolic compounds in fruit products: Methodology and perspectives

253rd National Meeting (2017)

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