ABSTRACT
Carotenoids are an important kind of natural pigment that can be widely found in plant-derived food and products. Although these compounds have been traditionally used in the food industry as colorants, nowadays they attract great attention since they have been discovered to possess several important functional properties, mainly antioxidant activity (Beutner et al., 2001; de Quiros and Costa, 2006; El-Agamey et al., 2004), as well as prevention of cardiovascular diseases (Arab and Steck, 2000; Rao and Rao, 2007), cancer (Nishino et al., 1999; Omoni and Aluko, 2005;), and macular degeneration (Snodderly, 1995). These properties make these compounds ideal for the always increasing functional food industry, as well as promoting the consumption of the natural products in which are contained. Citrus species are well known to possess a rich carotenoid pattern and are regarded as the most complex natural source of this type of compounds (Goodner et al., 2001). Although, in general, these compounds are widely distributed in nature and can be found in higher plants, algae, fungi, and bacteria (Jaime et al., 2007; Mendes-Pinto et al., 2004). The chemical structure of carotenoids is usually based in a C40 tetraterpenoid structure with a centrally located and extended conjugated double bond system, which acts as a light-absorbing chromophore and is related to the color shown. Taking into account their chemical structure, these compounds can be divided into two different groups: hydrocarbon carotenoids, generally named carotenes; and oxygenated carotenoids, commonly known as xanthophylls. This second group is the more complicated one in terms of number of compounds and variations in their structure. Xanthophylls can be found in either its free form (like are found the carotenes) or in a more stable fatty acid-esteri ed form, in the case of mono-and polyhydroxylated xanthophylls. During ripening, in some fruits the esteri cation degree of carotenoids increases; this has been directly linked to the transformation of the chloroplast into the chromoplast. Thus, in view of the fact that a single carotenoid could be found forming different esters, the already complex natural variability of carotenoids is often increased by the formation of these carotenoid esters. The information concerning the natural esteri ed form could help in the chemical characterization of citrus oils and, therefore, in the detection of contamination or adulteration occurring in the essential oil production industry.
