Carotenoids biological significance

Fruits and vegetables are generally high in water and low in fat, and, in addition to vitamins and minerals, they contain significant amounts of dietary fiber (DF) and phytochemicals—mainly polyphenols and carotenoids—with significant biological properties, including antioxidant activity. 

Biologic Significance. Besides being pigments, the carotenoids also participate in photosynthesis. Along with chlorophyll, they are structural and functional com-... 

Little is known about the biological significance of carotenoid epoxides. Karrer suggests that they might function as oxygen carriers. This question merits further attention. 

Fertile sources of carotenoids include carrots and leafy green vegetables such as spinach. Tomatoes contain significant amounts of the red carotenoid, lycopene. Although lycopene has no vitamin A activity, it is a particularly efficient antioxidant (see Antioxidants). Oxidation of carotenoids to biologically inactive xanthophyUs represents an important degradation pathway for these compounds (56). 

Often, low levels of carotenoids in biological samples provide significant challenges in quantification by HPLC-PDA alone. Electrochemical detection (ECD) has been successful in quantifying low concentrations of carotenoids (MacCrehan and Schonberger, 1987 Finckh et ah, 1995 Yamashita and Yamamoto, 1997). More information about ECD can be found in Chapter 2. ECD has also been successful in quantifying carotenoid isomers in foods, plasma, prostate tissue, cervical tissue, and buccal mucosal cells (Ferruzzi et ah, 1998,2001 Allen et ah, 2003 Unlu et ah, 2007). Electrochemical array detection for all-irans - 3-carotene has been reported to be 10 fmol on column, which is approximately 100-1000 times more sensitive than UVA is detectors (Ferruzzi et ah, 1998). 

Carotenoids are absorbed passively, dissolved in lipid micelles various studies have estimated the biological availability and absorption of dietary carotene as between 5% to 60%, depending on the nature of the food, whether it is cooked or raw, and the amount of fat in the meal. In addition, much of the carotene in foods is present as crystals that may not dissolve to any significant extent in intestinal contents (Parker, 1989 1996 Parker et al., 1999 Hickenbottom et al., 2002 Ribaya-Mercado, 2002 Tanumihardjo, 2002 Yeum and Russell, 2002). 

Carotenoids represent one of the broadest groups of natural antioxidants (over 600 characterized structurally) with significant biological effects and numerous industrial applications. Lycopene is a typical acyclic carotene that serves as a starting metabolite for formation of carotenoid derivatives via specific routes (p-carotene, torulene, etc.). Xanthophylls include hydroxy-, methoxy- oxo-, epoxy-, carboxy-, and aldehydic groups (torularhodin, zeaxanthin, astaxanthin, etc.), which results in a broad structural variety of carotenoid compounds. 

The antioxidant behavior of astaxanthin has been demonstrated in vivo as well. In Haematococcus algae, astaxanthin is accumulated as part of a stress response, and it is believed to protect cellular DNA from photodynamic damage. This carotenoid also protects lipids from peroxidation in trout and salmon. In chicks, astaxanthin supplementation suppressed the formation of lipid peroxides in the plasma. Significant biological antioxidant effects have been observed in vitamin E-deficient rats fed an astaxanthin-rich diet these include protection of mitochondrial function and inhibition of peroxidation of erythrocyte membranes. In two independent studies, lipid peroxidation in the seram and liver of astaxanthin-fed rats treated with carbon tetrachloride was... 

---