Historical and Introductory Aspects of Carotenoids

Carotenoids (also known as lipochromes) are multipurpose, mesmeric, multidimensional, multifaceted and challenging natural pigments. As secondary plant metabolites, they are remarkable for their wide dissemination, structural variety, and numerous actions. They perform essential and specialized i.e. both and primary secondary roles in plants. They are colorful and abundantly present class of isoprenoids which are synthesized photosynthetically (plants) and non-photosynthetically (fungi & bacteria). Innately, despite from few species of aphids, carotenoids are not been synthesized in animals, therefore, animals require them through daily diet. They exist in plant tissues as esterified (with fatty acids), forming complex (with proteins and sugars) or free forms (crystalline or amorphous). The conjugate double-bond (c.d.b.) system of carotenoid structure regulates biological functions, e.g. energy transfer, light absorption during photosynthesis, and defense from damaging properties of light in the photosynthesis. They share a common a skeleton formed by 2 isoprenoid units linked in such a way that the molecule is linear and has inverted symmetry in the center and several c.d.b. in the chain. All carotenoids retain their core structural and functional feature of carotenoids, i.e. polyene chain. Regardless of the presence of oxygen-containing groups, almost all carotenoids are hydrophobic. The carotenoids are responsible for biological activities, including photoprotection, photosynthesis, plant colors, and cell signaling. Health aspect of several carotenoids is undisputed.