Abstract
Phototrophic organisms including land plants, algae, and photosynthetic bacteria can synthesize carotenoids for photosynthesis. A part of bacteria and fungi also synthesize carotenoids. On the other hand, animals cannot synthesize carotenoids, and they ingest carotenoids from foods. Most animals can modify the carotenoids, such as oxidation and reduction. Humans contain usually six kinds of carotenoids: β-carotene, α-carotene, lycopene, β-cryptoxanthin, zeaxanthin, and lutein. Furthermore in this paper, functions of carotenoids in animals especially humans are briefly summarized: Carotenoids are essential for organisms living under oxygen to prevent active oxygen. β-Carotene is cleaved into retinal by β-carotene-15,15'-monooxygenase. Retinal is used as photoreceptor in eye. Lutein and zeaxanthin are accumulated in macula of eye for prevent blue light. From epidemiology, carotenoids in vegetables have anticancer activities. Lycopene might prevent prostatic cancer. Some carotenoids have also functions, such as antioxidant, anticancer, and anti-obesity.
