Quantitative analysis, in vitro assessment of bioavailability and antioxidant activity of food carotenoids—A review

This review discusses three important chemical/biochemical assays for food carotenoids. Considerable progress has been achieved in obtaining reliable quantitative data for food carotenoids with methods developed and validated, sources of errors and critical control points identified, interlaboratory studies conducted and certified references materials formulated. The carotenoid analyst should take advantage of these analytical refinements to avoid errors that can still be perceived in some published work. In vitro methods simulating gastric and small intestine digestive processes, coupled with highly differentiated cultures of Caco-2 cell, have been shown to be valid tools for the initial assessment of the relative bioavailability of carotenoids, allowing screening of large numbers of food samples. Comparative evaluation and standardization are still warranted, considering the marked discrepancy in results obtained by different laboratories. Current chemical assays grossly underestimate the antioxidant activity/capacity of food carotenoids. A set of methods needs to be developed and validated to have a biologically relevant appraisal of this activity, including measurement of the quenching of singlet oxygen, the primary mode of action of carotenoids as antioxidants, in addition to free radical scavenging, including other radicals aside from the peroxyl radical.