Carotenoids

Carotenoids 

yellow, orange, or red pigments (cyclic or acyclic isoprenoids) synthesized by bacteria, fungi, and higher plants.

Animals do not ordinarily form carotenoids, although they use them to synthesize vitamin A. The carotenoids include carotene and xanthophylls, which are widely found in plants; lyco-pene (C₄₀H₅₆), found in the fruits of the tomato, dog rose, and nightshade; zeaxanthin (C₄₀H₅₆O₂), found in corn kernels; vi-olaxanthin and flavoxanthin, found in squashes and gourds; cryptoxanthin (C₄₀H₅₆O), found in papaya; physalin (C₇₂H₁₁₆₋O₄), found in the flowers and fruits of Physalis; fucoxanthin (C₄₀H₅₆O₆), found in brown algae; crocetin (C₂₀H₂₄O₄), found in the stigmata of saffron; and taraxanthin (C₄₀H₅₆O₄), found in the flowers of snapdragon and coltsfoot. The relative content of the various carotenoids changes in the course of development of the plant and under the influence of environmental conditions. The concentration of carotenoids is highest in the plastids of the cells.

Carotenoids promote the fertilization of plants by stimulating the germination of pollen and the growth of the pollen tubes. They play a part in the absorption of light by plants and in the perception of light by animals. They are also a major factor in the processes of photosynthesis and oxygen transport in plants. The number and position of the double bonds in the molecules of the carotenoids determine their color; over 150 carotenoids (pigments) are known. Carotenoids with a larger number of double bonds absorb in the long-wave part of the spectrum, and their color is bright orange or red.

REFERENCES

Goodwin, T. SramiteVnaia biokhimiia karotinoidov. Moscow, 1954. (Translated from English.)
Kretovich, V. L. Osnovy biokhimii rastenii, 5th ed. Moscow, 1971.

K. E. OVCHAROV