engleski

Impact of cyclodextrin encapsulation on in vitro bioavailability of hydroxytyrosol and tyrosol from olive pomace extract

Due to their proven health-promoting properties, increasing efforts are being made to find sustainable and efficient ways to extract polyphenols from olive pomace and formulate them into stable products. Namely, their further utilization is often limited by inadequate physicochemical properties, extensive degradation during storage or low bioavailability. Some of these limitations can be successfully overcome by utilization of encapsulated polyphenols, instead of free compounds. The aim of this study was to investigate the impact of cyclodextrin encapsulation used for preparation of stable and organoleptically acceptable dry olive pomace extracts, on in vitro bioavailability of hydroxytyrosol and tyrosol from obtained formulations. Microencapsulation was achieved by freeze-drying of olive pomace extracts with different types of cyclodextrins (CDs): βCD, randomly methylated βCD, hydroxypropyl β-CD, and γ-CD. Gastrointestinal stability and bioavailability of encapsulated antioxidants were investigated by two in vitro approaches: dializability and Caco-2-cell permeability. Content of hidroxytyrosol and tyrosol in different sample fractions obtained during simulation of gastrointestinal digestion was compared to results obtained by analysing the gastrointestinal stability of native formulation (N) prepared without the addition of cyclodextrins. During gastric phase, the content of tyrosol was significantly reduced (51-64%) while the content of hydroxytyrosol significantly increased, probably as the result of gastric degradation of other complex polyphenolic compounds resulting with hydroxytyrosol formation. Their content remained relatively unchanged during the intestinal phase of digestion. Significant correlation was obtained between dializability and transephitelial permeability of both, hydroxytyrosol and tyrosol. Both parameters were negatively influenced by the presence of CDs in the formulation, possibly due to formation of cyclodextrin aggregates that may occur under the simulated conditions of small intestine. Among investigated cyclodextrins, γ- CD showed the least negative effect on dializability and transephitelial permeability of hydroxytyrosol and tyrosol, reducing them by 15% on average, in comparison to native sample.

hydroxytyrosol, tyrosol, in vitro bioavailability, olive pomace

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