Improved bioaccessibility and antioxidant capacity of olive leaf (Olea europaea L.) polyphenols through biosorption on Saccharomyces cerevisiae

• The potential use of S. cerevisiae as biosorbent was examined.
• 10 g/L of S. cerevisiae allowed the highest phenolics recovery.
• Biosorption improved bioaccessibility of phenolics in infusions and suspensions.
• Digestion increased total soluble polyphenols and antioxidant capacity.
• Oleuropein and hydroxytyrosol showed high stability after in vitro digestion.

Olive (Olea europaea L.) leaves (OL) are natural by-products that can be used as an advantageous rich source of bioactive compounds, especially polyphenols. This study investigated the potential use of Saccharomyces cerevisiae as a new carrier of OL antioxidants and a means to protect their bioactivity during simulated gastrointestinal digestion. The biosorption on S. cerevisiae allowed the recovery of 25.17 mg/g and 49.40% of the polyphenols from olive leaf (var. Chemlali) infusions. Both infusions and suspensions before and after biosorption were analyzed for total soluble polyphenols and total antioxidant capacity (oxygen radical absorbance capacity (ORAC) and trolox equivalent antioxidant capacity (TEAC) assays). On the other hand, the effect of the interactions with the yeast cell wall on the bioaccessibility of the phenolic compounds was investigated. At the end of the in vitro gastrointestinal digestion, all the samples after biosorption had higher release rates of phenolics than before biosorption with significantly (p < 0.05) higher antioxidant capacity. In the present study, the stability of oleuropein and hydroxytyrosol in the gut was suggested to enhance the antioxidant activity of the in vitro digests as verified by Triple TOF–LC–MS–MS method. Interestingly, hydroxytyrosol showed high bioaccessibility. Finally, S. cerevisiae constitutes a promising delivery system of these main polyphenols.

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