CHapTer 9 Metabolic Fate of Bioaccessible and Non-bioaccessible Carotenoids TorsTen BoHn Luxembourg Institute of Health (LIH), population Health Department, rue 1 a-B, Thomas edison, L-1445 strassen, Luxembourg *e-mail:
[email protected] 9.1 Introduction Carotenoids are among the most abundant lipophilic secondary plant compounds consumed in the diet. Carotenoids include mostly C-40 tetra- terpenoids, though also C-30 tri-1 and C-50 pentaterpenoids2 have been reported, at least in various bacteria, though due to their minute intake, they are not of dietary relevance. However, their dietary variety is increased when also counting the many apo-carotenoids (i.e. carotenoid metabolites derived from oxidative cleavage of carotenoids, which may occur in bacteria, fungi and plants, but also in animals).3 Major plant-derived apo-carotenoids include, for example, bixin, crocin, picrocrocin, abscisic acid, strigolactone and mycorradicin.4 Though several hundreds of carotenoids have been described in nature, it is estimated that only a few dozen or so predominate in our daily diet.5,6 Their dietary intake as well as circulating blood levels have been related to Food Chemistry, Function and Analysis No. 5 Non-extractable Polyphenols and Carotenoids: Importance in Human Nutrition and Health Edited by Fulgencio Saura-Calixto and Jara Pérez-Jiménez © The Royal Society of Chemistry 2018 Published by the Royal Society of Chemistry, www.rsc.org 165 166 Chapter 9 the reduced risk of several chronic diseases, including certain cardiometa- bolic conditions such as the metabolic syndrome7 and certain types of can- cer,8,9 but also allergies10 and asthma.11 a carotenoid health index based on total plasma carotenoids has been proposed by Donaldson, with <1 µM total carotenoids constituting a very high health risk12 regarding total mortality (lower threshold), and less so for metabolic syndrome and cancer (higher threshold).