Phenolic compounds and biological rhythms: Who takes the lead?

Abstract Background Phenolic compounds are one of the most heterogeneous group of plant secondary metabolites with over 50,000 diverse molecules identified so far. Despite the low bioavailability of native forms, they have been shown to exert several beneficial effects against chronic diseases such as diabetes, cardiovascular disease, and neurodegenerative diseases. There are different factors that may affect their absorption and distribution in tissues, but the exact mechanisms remain unclear. Recently, the time of the day and the season of the year in which they are consumed have emerged as another factor that may significantly impact on their metabolism and bioactivities. Scope and approach This review emphasizes the importance of the interaction between phenolic compounds and biological rhythms and its impact on the bioactivities of these metabolites. This may have implications for the food industry as food rich in phenolic compounds may exert different effects depending on the time of consumption. Key findings and conclusions Phenolic compounds broad activity could be explained by their extensive transformation, including metabolization in the colon by the gut microbiota, which leads to the production of multitude of different metabolites. Biological rhythms play a significant role in this metabolism affecting their bioactivities and, at the same time, phenolic compounds may exert their effects by promoting homeostasis at a basal signalling level through interactions with the biological clock system. This is in accordance with the xenohormesis hypothesis, which explains that chemical cues synthetized by plants are able to allow animals to favourably adapt to changing environmental conditions.