Xanthophylls esterification

Homero-Mendez D, Minguez-Mosquera Ml (2000) Xanthophyll esterification accompanying carotenoid overaccumulation in chromoplasts of Capsicum annuum ripening fruits is a constitutive process and useful for ripeness index. J Agric Food Chem 48 1617-1622... 

The degree of linkage of a compound may also affect its bioaccessibility in the gut. It is generally admitted that a compound linked with other molecules (e.g., via esterification, glycosylation, etc.) is not absorbed as well as its free form and thus it must be hydrolyzed in the gut in order to be taken up by enterocytes. Due to the presence of hydroxyl or keto groups on their molecules, the xanthophylls (lutein, zeaxanthin, and P-cryptoxanthin) are found in both free and esterified (monoester or diester) forms in nature, but few studies have been conducted to date to assess the bioavailabilities of these esters. 

Alkaline hydrolysis (saponification) has been used to remove contaminating lipids from fat-rich samples (e.g., pahn oil) and hydrolyze chlorophyll (e.g., green vegetables) and carotenoid esters (e.g., fruits). Xanthophylls, both free and with different degrees of esterification with a mixture of different fatty acids, are typically found in fruits, and saponification allows easier chromatographic separation, identification, and quantification. For this reason, most methods for quantitative carotenoid analysis include a saponification step. 

Xanthophyll esters are common in fruits and vegetables. Few data exist regarding the effect of carotenoid esterification on carotenoid bioavailability. Xanthophyll esters are readily broken in the human intestine (West and Castenmiller 1998 Breithaupt and others 2003 Faulks and Southon 2005). Chitchumroonchokchai and Failla (2006) demonstrated that hydrolysis of zeaxanthin esters increases zeaxanthin bioavailability. Wingerath and others (1995) did not find (3-cryptoxanthin esters in chylomicrons from humans fed with tangerine juice. Herbst and others (1997) demonstrated that lutein diesters are more bioavailable than free lutein. However, the question of whether the free or the esterified form is more bioavailable to humans is still an ongoing discussion. 

Despite the existing evidence attesting to the safety of dietary astaxanthin, little is known about the bioavailability and metabolism of this carotenoid in humans. Several steps are involved in the assimilation of carotenoids by mammals, including transfer from the food matrix, transfer to lipid micelles in the small intestine, uptake by intestinal mucosal cells, transport to the lymph system, and eventually, deposition of the carotenoid or its metabolites in specific tissues. " A number of factors can influence the progression of these steps, including the nature of the food matrix, " the structure of the carotenoid (including potential esterification and the nature of its isomeric composition), the presence of other carotenoids, " and the amount and types of lipids in the diet. Overall, human metabolism of astaxanthin should be somewhat similar to that of the other xanthophylls, but subtle differences are expected. 

Sugawara, T., Yamashita, K., Asai, A., Nagao, A., Shiraishi, T., Imai, I., and Hirata, T. (2009). Esterification of xanthophylls by human intestinal Caco-2 cells. Arch. Biochem. Biophys. 483, 205-21Z... 

In processed food, the maceration reduces the particle size and removes some barriers, increases the contact superficies for interaction with digestive. Effectors, such as the presence of oil, can also have an influence on the bioaccessibUity and/or bioavailability of carotenoids these compounds are lipophilic molecules, and they have to be incorporated in mixed micelles in the duodenum before they can be absorbed in the mucosa [31]. Certain structural differences may alter fat solubility and modify the efficiency of the micellization. One of them is the esterification of xanthophyll with fatty acids. Esterified xanthophylls exhibit increased fat solubility relative to their corresponding free xanthophylls and even against carotenes. 

As shown in Table 1 Titavit treatment stimultated to a high extent carotenoid formation, specially p-carotene and red coloured xanthophylls (capsorubin and capsanthin). Esterification of capsanthin with fatty acids increased 1.4 times as a function of Titavit treatment. This was accompanied by structural change on the chromoplast. The fatty bodies disappeared and the fibriles became much thicker in chromoplast from Titavit-treated fruits. 

Biosynthesis of K-carotenes proceeds simultaneously with esterification of pigments by fatty acids. The majority of pigments of mature peppers (about 80%) are totally or partially esterified with fatty acids. The main fatty acids of yellow xanthophylls are hnoleic, myristic and palmitic acids, in red xanthophylls they are mainly bound lauric, myristic and palmitic acids. 

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