Chlorophyll and carotenoids

Light and photosynthetic electron transport convert DPEs into free radicals of undetermined stmcture. The radicals produced in the presence of the bipyridinium and DPE herbicides decrease leaf chlorophyll and carotenoid content and initiate general destmction of chloroplasts with concomitant formation of short-chain hydrocarbons from polyunsaturated fatty acids (37,97). 

Gross, J., Chlorophylls, in Pigments in Vegetables Chlorophylls and Carotenoids, Gross, J., Ed., Van Nostrand Reinhold, New York, 1991, 2. 

Both chlorophylls and carotenoids occur in all green leaves, but their color is masked by chlorophyll in photosynthetic tissues. When the chlorophylls break down as leaves senesce (mature), the yellow and orange carotenoids persist and the leaves turn yellow. Carotenoids are responsible for the colors of familiar animals such as lobsters, flamingos, and fish. Often people are unaware of the chemical nature of food colorants. ... 

Lichtenhaler, H.K., Chlorophylls and carotenoids pigments of photosynthetic biomembranes, Meth. EnzymoL, 148, 350, 1987. 

Gross, J., Chlorophyll and carotenoid pigments of pigment of grapes (Vitis vinifera L.), Gartenbauwiss, 49, 180, 1984. 

Lisiewska, Z., Kmiecik, W., and Shnpski, J., Contents of chlorophylls and carotenoids in frozen dill effect of nsahle part and pre-treatment on the content of chlorophylls and carotenoids in frozen diU (Anethum graveolens L.), depending on the time and temperature of storage. Food Chem., 84, 511, 2004. 

Because plants present chlorophylls and carotenoids simultaneously, it may be useful to separate both groups from each other in a laboratory or preparative scale in order to avoid contamination in further purification steps, mainly when they are prepared in large amounts. Clean-up procedures using an open column packed with absorbents such as alumina, magnesia, polyethylene powder, powdered sucrose, DEAE-Sepharose, starch, cellulose, or MgO HyfloSupercel are good approaches. MgO HyfloSupercel in a proportion of 1 1 or 1 2 is the usual adsorbent. Sucrose and cellulose are interesting as they do not alter the chlorophylls, but they are tedious to work with. 

Many other authors, as reviewed extensively by Schwartz and Lorenzo, and by Eder improved the C18 RP-HPLC methods that have been largely applied using similar but not exactly identical systems to separate and to quantify complex mixtures of chlorophylls and carotenoids. 

Schoefs, B., Chlorophyll and carotenoid analysis in food products. A practical case-by-case view. Trends Anal. Ghent., 22, 335, 2003. 

Gandul-Rojas, B., Roca, M., and Mmguez-Mosquera, M.L, Chlorophyll and carotenoid degradation mediated by thylacoid-associated peroxidative activity in olives (Olea europaea) cv. Hojiblanca, J. Plant. Physiol., 161, 499, 2004. 

Mantoura, R.F.C. and Llewellyn, C.A., The rapid determination of algal chlorophyll and carotenoid pigments and their breakdown products in natural waters by reversed-phase high-performance liquid chromatography, A a/. Chim. Acta, 151, 297, 1983. 

When light from all three channels excites the fluorescence of crystalline individual compounds such as allelochemicals flavonoids quercetin and rutin or pigments of plant cells - azulene, chlorophyll and carotenoids fluoresce in different regions of the spectra in yellow and red or blue, red and yellow-orange, respectively (Fig. 7). It compares the light emission of the substances within cellular structures. 

Gross J. 1982a. Changes of chlorophylls and carotenoids in developing strawberry fruits (Fragariaanonassa) cv. Tenira. Gartenbauwiss 47 142—144. 

Gross J. 1982c. Chlorophyll and carotenoid pigments in Ribes fruits. Sci Hort 18 131—136. 

Chloroplasts (29-36) are the sites of photosynthesis and their ribosomes can carry out protein synthesis. Chloroplasts that contain chlorophylls and carotenoids, are disc shaped and 4-6 pm in diameter. These plastids are comprised of a ground substance (stroma) and are traversed by thylakoids (flattened membranous sacs). The thylakoids are stacked as grana. In addition, the chloroplasts of green algae and plants contain starch grains, small lipid oil droplets, and DNA. 

Chlorophylls occur very frequently in the plant kingdom, they are responsible for the colour of vegetables and some fruits. They also occur in algae and several bacteria. Chlorophylls in plants are photoreceptors and in photosynthesis the presence of a closed circuit of conjugated double bonds allows them to absorb light. Because of their predominant importance as photoreceptors a considerable number of analytical methods have been developed for the separation and quantitative determination. The analytical methods applied for the measurement of chlorophylls and carotenoids in food products have been reviewed previously [273],... 

H.W. Higgins and DJ. Mackey, Algal class abundances, estimated from chlorophyll and carotenoid pigments, in the western Equatorial Pacific under El Nino and non-El Nino conditions. Deep Sea Res. 47 (2000) 1461-1483. 

Gross J (1991) Pigments in vegetables chlorophylls and carotenoids. Van Nostand Reinhold, New York, NY... 

The electron-carrying cofactors of PSI and the lightharvesting complexes are part of a supramolecular complex (Fig. 19-51a), the structure of which has been solved crystallographically. The protein consists of three identical complexes, each composed of 11 different proteins (Fig. 19-51b). In this remarkable structure the many antenna chlorophyll and carotenoid molecules are... 

Many of the colors associated with higher plants (green leaves in the spring and summer, yellow or red leaves in the fall, the orange color of carrots, some colors in flower petals) are due to the presence of pigment molecules such as chlorophylls and carotenoids. In this experiment a mixture of these pigments will be isolated by solvent extraction of plant tissue, separated by chromatography, and the components identified by visible spectrophotometry. 

The intense colors of the chlorophylls and carotenoids make them ideal candidates for absorption spectroscopy studies (Tan and Soderstrom, 1989). In fact, each plant pigment studied in this experiment has a unique visible spectrum that can provide a positive identification. As shown in Figure E8.3, chlorophylls a and b have absorption maxima in the 600-675 and... 

In order to determine the chlorophyll and carotenoid content of your extract, you must measure the absorbance at several wavelengths, 661.6, 644.8, and 470 nm. If you are using a single-beam spectrophotometer, use a cuvette of acetone to zero the instrument at each wavelength. A double-beam instrument should have a cuvette of acetone in the reference beam and the acetone extract solution in the sample beam. If desired, it is instructive to obtain a complete spectrum of the extract in the range 400-700 nm. This can be compared to the spectrum obtained for each of the individual pigments in part D. 

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