Carotenoid

About: Carotenoid is a research topic. Over the lifetime, 6657 publications have been published within this topic receiving 296374 citations. The topic is also known as: carotenoids & tetraterpenoids.

Chlorophylls and carotenoids: Pigments of photosynthetic biomembranes

Abstract: Publisher Summary This chapter presents detailed information on chlorophylls and carotenoids to give practical directions toward their quantitative isolation and determination in extracts from leaves, chloroplasts, thylakoid particles, and pigment proteins. The chapter focuses on the spectral characteristics and absorption coefficients of chlorophylls, pheophytins, and carotenoids, which are the basis for establishing equations to quantitatively determine them. Therefore, the specific absorption coefficients of the pigments are re-evaluated. This is achieved by using a two-beam spectrophotometer of the new generation, which allows programmed automatic recording and printing out of the proper wavelengths and absorbancy values. Several procedures have been developed for the separation of the photosynthetic pigments, including column (CC), paper (PC), and thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC). All chloroplast carotenoids exhibit a typical absorption spectrum that is characterized by three absorption maxima (violaxanthin, neoxanthin) or two maxima with one shoulder (lutein and β-carotene) in the blue spectral region.

Determinations of total carotenoids and chlorophylls a and b of leaf extracts in different solvents

Abstract: Various equations for the determinations of total chlorophyll and individual amounts of chlorophylls a and b in extracts from plant tissues exist (see Holden, 1976) and some of them (e.g. Arnon, 1949) are widely used. Additional modifications to the equations have also been developed so as to permit an estimate of total carotenoids to be made from the spectrum of the same mixture in diethyl ether (Ziegler & Egle, 1965; Gaudillire, 1974). During the course of studies that involved the use of various solvents we noted large discrepancies (>40%) between estimations made using the different published equations for particular solvents, all of which were known to contain the same amount of pigments. Taking advantage of a t.1.c. method (Lichtenthaler 8t Pfister, 1978) that permits a distinct separation of the two chlorophylls and also the major carotenoids using light petroleum (b.p. 40-6O0C)/dioxane/propan-2-ol (7 :3 : 1, by vol.) as developing solvent, fresh samples of chlorophyll a and b uncontaminated with each other were readily available for re-evaluation of the published specific absorption coefficients. Those values published by Smith & Benitez (1955), using diethyl ether, were found to be still the most acceptable, and relative specific absorption coefficients to these values were established (Table 1) for various other solvents. The red peak maxima of the chlorophylls were shifted to longer wavelengths with increasing polarity of the solvents; in our case diethyl ether, acetone, 80% (v/v) acetone, 96% (v/v) ethanol and methanol. The red absorption peaks of the chlorophylls were also broadened in the same sequence and the values for the specific absorption coefficients decreased. At the same time suitable values for total carotenoids at 470nm were also determined. On the basis of these coefficients the following equations were derived to determine the individual levels of both chlorophyll a (C,) and chlorophyll b (C,) and the total amounts of carotenoids (Cx+c) and chlorophylls (C,+ C,) [in pg.(ml of plant extract)-'] the measured absorbance values (A) at different wavelengths:

Biosynthesis of plant pigments: anthocyanins, betalains and carotenoids

Abstract: Plant compounds that are perceived by humans to have color are generally referred to as 'pigments'. Their varied structures and colors have long fascinated chemists and biologists, who have examined their chemical and physical properties, their mode of synthesis, and their physiological and ecological roles. Plant pigments also have a long history of use by humans. The major classes of plant pigments, with the exception of the chlorophylls, are reviewed here. Anthocyanins, a class of flavonoids derived ultimately from phenylalanine, are water-soluble, synthesized in the cytosol, and localized in vacuoles. They provide a wide range of colors ranging from orange/red to violet/blue. In addition to various modifications to their structures, their specific color also depends on co-pigments, metal ions and pH. They are widely distributed in the plant kingdom. The lipid-soluble, yellow-to-red carotenoids, a subclass of terpenoids, are also distributed ubiquitously in plants. They are synthesized in chloroplasts and are essential to the integrity of the photosynthetic apparatus. Betalains, also conferring yellow-to-red colors, are nitrogen-containing water-soluble compounds derived from tyrosine that are found only in a limited number of plant lineages. In contrast to anthocyanins and carotenoids, the biosynthetic pathway of betalains is only partially understood. All three classes of pigments act as visible signals to attract insects, birds and animals for pollination and seed dispersal. They also protect plants from damage caused by UV and visible light.