Carotenoids are a family of natural pigments extensively present in the vegetable kingdom, photosynthetic microorganisms, and some fungi, which mains function are their contribution to the light-harvesting process, the filtering of deleterious light radiations and the antioxidant activity.

The benefit of carotenoids to human health is undeniable and consequently, their use for this purpose is growing rapidly. Additionally, the nutraceutical properties of carotenoids have attracted the attention of the food industry, especially in a new market area, the 'cosmeceuticals.'

Marine organisms (microalgae, seaweeds, animals, etc.) are a rich source of carotenoids, with optimal properties for industrial production and biotechnological manipulation.

Consequently, several papers have reviewed the analysis , characterization, extraction and determination methods, biological functions and industrial applications.

But, now, the bioaccessibility and bioactivity of marine carotenoids have not been focused on any review, although important achievements have been published. The specific and diverse character of the marine matrix determines the bioavailability of carotenoids, some of them unique in nature.

The bioavailability

Considering the importance of the bioavailability not just from the health and nutritional point of view but also to the food and pharmaceutical industry, we consider that the present review responds to an actual demand.

Taking both topics into account, this review comprehends those significant contributions made to date regarding the bioaccessibility issues of those marine carotenoids we hope to obtain from sources or from supplements.

In vitro experiments and in vivo studies, either with animal models of humans applied to fucoxanthin and astaxanthin have provided several hints of their absorption, metabolism and tissue distribution .

Hence, pharmacokinetic parameters and some transformation routes have been unraveling or at least tentatively denoted and a significant amount of data has been produced, which is evaluated in this revision.

References to other carotenoids that we can obtain from marine source but that have their 'terrestrial sources' counterparts are also acknowledged. Finally, and considering the meaning of aquaculture practice and that bioaccessibility of marine carotenoids to farmed animals is a topic that is in continuous progress, a section is focused on bioaccessibility of marine carotenoids in aquaculture.