Polyphenol lipophilisation: a suitable tool for the valorisation of natural by-products

Polyphenols represent one of the most widely distributed molecules in vegetables and fruits with interesting functional and biological properties (antioxidant, antifungal, etc.). By-products issued from agro-industrial processing represent an inexpensive source of polyphenols; these phenolic compounds can then be extracted and transformed into functional molecules to be used as additives for the food or cosmetic industries. With the objective to enhance polyphenol's natural properties, considering their low hydrophobicity, lipophilisation of the isolated phenolic compounds was accomplished. The first lipophilisation of ellagitannins issued from pomegranate peel was carried out and, based on our previous work, polyphenols (an anthocyanin and a phenolic acid) extracted from hibiscus flowers were successfully lipophilised. In order to evaluate the impact of lipophilisation on the main properties of these compounds, protocatechuates with different alkyl chain lengths were assessed for their antifungal capacity against a worldwide distributed pathogenic fungus (Fusarium oxysporum), and the new synthesised ellagitannins esters were studied for their antiradical activity in vitro. The results showed that, depending on the chain length, lipophilisation improved the functional properties of the original phenolics. This could be an innovative way to synthesise molecules with an enhanced potential as antioxidants in food, cosmetics or related products.