Health-promoting phenolic compounds in extra virgin olive oil: an integrated study of their concentration and bioavailability

Abstract

The health promoting attributes associated with following a traditional Mediterranean diet have been reviewed extensively. The principal source of dietary fat in the Mediterranean diet is Extra virgin olive oil (EVOO) that contribute significantly to the superior health profile observed in Mediterranean populations. Between its minors compounds, EVOO contains at least 30 phenolic compounds (PCs) and has been classified according to their chemical structure into the following main classes: phenolic acids, lignans, flavonoids, phenolic alcohols, secoiridoids (SEC). Regarding this last group, these compounds are responsible for the sensory features of EVOO, mainly the bitter and pungent mouthfeel. Oleocanthal (OLC) and oleacein (OLEA) appear the main compounds responsible for the mouthfeel perceptions, respectively. Moreover, they are the most studied and best-known components in terms of health protecting activities. In this sense, the potential protective role exerted by SECs from EVOO in cancer, cardiovascular, neurodegenerative, aging‐related, and immunoinflammatory diseases has been studied. The data obtained so far has clearly shown that SECs has proven biological activity, including antioxidant and antimicrobial properties, anti-inflammatory effects, anticancer properties and neuro- protective effects, among others. The phenolic concentration and composition of EVOO together with the degree to which these components are absorbed and metabolized are essential in determining the health effects associated with such compounds. Several factors have been shown to affect the concentration of PCs in EVOO and these include olive fruit cultivar and variety, region of growth, agricultural cultivation techniques, maturity at harvest, processing, and storage. In this thesis the study of the main factors affecting the PCs concentration is covered. Regarding its bioavailability after EVOO dietary intake has been a topic of increasing research in recent years. Bioavailability is a complex process involving several different stages that include liberation, absorption, distribution, metabolism and elimination phases. For polyphenols, this principally involves the following digestive processes: i) release of polyphenols from the food matrix; ii) changes in PCs during gastric/small-intestinal digestion; iii) cellular uptake of aglycons and some conjugated polyphenols by enterocytes; iv) microbiological fermentation of nonabsorbed polyphenols or those re-excreted via bile or the pancreas to yield additional metabolites, v) phase I/II enzyme modifications that occur upon uptake in the small intestine and/or colon; vi) transport in the bloodstream and subsequent tissue redistribution; and vii) excretion via the kidney or re-excretion into the gut via bile and pancreatic juices. Since many in vitro, in situ, in vivo and clinical studies, have demonstrated the protective effect of SECs, in this thesis we set out to evaluate the intestinal absorption and metabolism of OLC and OLEA for a better understanding of the biological effects attributed to these compounds.

In addition, a tissue distribution of OLC and OLEA and its metabolites also was study after the oral administration of enriched refined olive oil. Target tissues likes as brain, hearth, lungs, among other were evaluated to determine the biological concentrations usually achieved when following a Mediterranean diet.