The bioavailability of natural antioxidants remains a critical challenge in the development of effective nutraceuticals. Instability during digestion and limited intestinal absorption often compromise the efficacy of these compounds when administered orally. Encapsulation technologies offer a promising approach to improve the stability and absorption of natural compounds, particularly those derived from agri-food by-products, contributing to their valorisation.
The aim of this work is to obtain encapsulated olive leaf extract formulations and to evaluate the available fraction and intestinal permeability of these formulations. An in vitro gastrointestinal digestion test was carried out according to the harmonised INFOGEST protocol, in which the fluids and enzymatic processes of the oral, gastric and intestinal phases are successively simulated. This was followed by an intestinal permeability test using the Caco-2 cell monolayer model. For this, samples of fully digested formulations were placed in the donor chamber, and samples were collected from the acceptor chamber at different time points. Transport across the membrane in both directions from the apical or basolateral domain of the epithelium was also studied. The major component of the extract in all samples was quantified by high-performance liquid chromatography coupled to mass spectrometry.
Apparent permeability coefficients were calculated in the apical–basolateral direction and vice versa, allowing for the calculation of the efflux ratio and for the assessment of the type of transport and the permeation rate. Three of the four encapsulated formulations showed moderate permeability values, together with the non-encapsulated extract. Formulation B showed significant differences; however, formulation C decreased the efflux rate, which, together with a higher available fraction, improved the permeation rate. This evaluation provides information on the usefulness of encapsulation in enhancing the absorption of bioactive compounds, useful for the development of more effective nutraceutical products.
