Methods for predicting absorption

The measurement of carotenoid absorption is fraught with difficulties and riddled with assumptions, and it is therefore a complex matter. Methods may rely on plasma concentration changes provoked by acute or chronic doses, oral-faecal mass balance method variants and compartmental modelling. 

Classically, to measure absolute absorption the plasma area imder the curve from an intravenous dose would be compared to that caused by the feeding of an oral dose. However, the carotenoids are lipid-soluble and are normally incorporated in chylomicrons synthesised in the enterocytes, a situation that cannot be replicated and applied to studies in humans because an intravenous preparation that would behave naturally is not possible. 

The single acute dose method can be applied to whole plasma studies if the dose can be discriminated from the endogenous background. Discrimination 

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A possible method for predicting absorption bandwidths of chromogenic molecules or FBAs using PPP-MO theory (section 1.5) has been devised. It is based on the empirical linear relationship stated by the Pestemer rule. Thus theoretical Stokes shifts are computed by the PPP-MO method and related to bandwidths. The requisite MO parameters for various typical absorption bands have been developed for use in these calculations. Reasonable correlation between calculated and experimental half-bandwidth data was found, suggesting that this approach has practical potential in predicting colour tone and brightness intensity [ 19]. 

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