Multiple-approach studies to assess anthocyanin bioavailability

Anthocyanins that are commonly ingested from the diet are largely conjugated, metabolized by colon microbiota and excreted in the urine and feces, yielding in a rather low bioavailability. Nevertheless, there are several health-promoting properties attributed to the ingestion of dietary anthocyanins including cardiovascular and neuroprotective effects, and the prevention of some types of cancer. There are many doubts on which compounds are really involved and which are the molecular mechanisms underlying all those biological events. Some evidences have come forth supporting the idea that the dietary phenolics bioactive forms in vivo are not necessarily those which occur in nature, but rather conjugates or metabolites arising from them in the human body. So far, it has been quite difficult to clearly assess both native and metabolized forms in vivo and to distinguish their different biological roles. Also, although some anthocyanins bioavailability has been reported to be low, their tissue distribution and accumulation has to be considered. This may lead to an increase of their levels in some key targets. This feature would be likely to contribute to possible different biological properties of dietary anthocyanins depending on their biological target. The several approaches that have been undertaken to assess anthocyanin bioavailability have been reviewed herein.