Hydroxytyrosol and tyrosol are dietary phenolic compounds present in virgin olive oil and wine. Both compounds are also endogenously synthesized in our body as byproducts of dopamine and tyramine metabolisms, respectively. Over the last decades, research into hydroxytyrosol and tyrosol has experienced an increasing interest due to the role that these compounds may play in the prevention of certain pathologies (e.g. cardiovascular, metabolic, neurodegenerative diseases and cancer). The translation of promising in vitro and in vivo biological effects from preclinical studies to the context of human disease prevention initially depends on whether the dose ingested becomes available at the site of action. In this regard, information regarding the bioavailability and metabolic disposition of hydroxytyrosol and tyrosol is of most importance to evaluate the impact they may have on human health. In this review, we discuss and summarize the state of the art of the scientific evidence regarding the processes of absorption, distribution, metabolism and excretion of both hydroxytyrosol and tyrosol. We also examine the impact of these compounds and their metabolites on biological activity in terms of beneficial health effects. Finally, we evaluate the different analytical approaches that have been developed to measure the plasma and urinary levels of hydroxytyrosol, tyrosol and their metabolites.

Strong adherence to a Mediterranean diet is associated with improved cognitive function and a lower prevalence of mild cognitive impairment. Olive oil and red wine are rich sources of polyphenols which are responsible in part for the beneficial effects on cognitive functioning. Polyphenols induce endogenous antioxidant defense mechanisms by modulating transcription factors such as the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). This review discusses the scientific data supporting the modulating effect of olive oil and red wine polyphenols on Nrf2 expression, and the potential health benefits associated with cognitive functioning.

Beer is a fermented beverage with beneficial phenolic compounds and is widely consumed worldwide. The current study aimed to describe the content of three families of phenolic compounds with relevant biological activities: prenylated flavonoids (from hops), simple phenolic alcohols (from fermentation) and alkylresorcinols (from cereals) in a large sample of beers (n = 45). The prenylated flavonoids analyzed were xanthohumol, isoxanthohumol, 6- and 8-prenylnaringenin. The total prenylated flavonoids present in beer ranged from 0.0 to 9.5 mg/L. The simple phenolic alcohols analyzed were tyrosol and hydroxytyrosol, ranging from 0.2 to 44.4 and 0.0 to 0.1 mg/L, respectively. Our study describes, for the first time, the presence of low amounts of alkylresorcinols in beer, in concentrations ranging from 0.02 to 11.0 µg/L. The results in non-alcoholic beer and the differences observed in the phenolic composition among different beer types and styles highlight the importance of the starting materials and the brewing process (especially fermentation) on the final phenolic composition of beer. In conclusion, beer represents a source of phenolic compounds in the diet that could act synergistically, triggering beneficial health effects in the context of its moderate consumption.

Ferulic acid (FA) is a polyphenol pertaining to the class of hydroxycinnamic acids present in numerous foods of a plant origin. Its dietary consumption leads to the formation of several phase I and II metabolites in vivo, which represent the largest amount of ferulates in the circulation and in the intestine in comparison with FA itself. In this work, we evaluated their efficacy against the proinflammatory effects induced by lipopolysaccharide (LPS) in intestinal Caco-2 cell monolayers, as well as the mechanisms underlying their protective action. LPS-induced overexpression of proinflammatory enzymes such as inducible nitric oxide synthase (iNOS) and the consequent hyperproduction of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) were limited by physiological relevant concentrations (1 µM) of FA, its derivatives isoferulic acid (IFA) and dihydroferulic acid (DHFA), and their glucuronidated and sulfated metabolites, which acted upstream by limiting the activation of MAPK p38 and ERK and of Akt kinase, thus decreasing the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB) translocation into the nucleus. Furthermore, the compounds were found to promote the expression of Nrf2, which may have contributed to the downregulation of NF-ĸB activity. The overall data show that phase I/II metabolites retain the efficacy of their dietary free form in contrasting inflammatory response.