Green vegetables chlorophylls, extraction

Khachik, R, Beecher, G.R., and Whittaker, N.R, Separation, identification and quantification of the major carotenoid and chlorophyll constituents in extracts of several green vegetables by liquid chromatography, J. Agric. Food Chem., 34, 603, 1986. 

The isomerization of all-trans-[3-carotene under N2 atmosphere by photosensitization action of eight chlorophyll compounds naturally present in the extracts of green vegetables was investigated by illumination with fluorescent white light (3000 lux) at 12°C to minimize the thermal degradation (O Neil and Schwartz 1995). All chlorophylls showed similar isomeric distribution and efficiency, 9-d.s- 3-carotene is the main isomer formed. On the other hand, the illumination of all-fran.s-(3-car-otene without chlorophylls indicated that the main isomer formed was 13-d.s- 3-carotcnc, probably due to the population of a different triplet state manifold by direct photolysis. 

Green coloration, present in many vegetable oils, poses a particular problem in oil extracted from immature or damaged soybeans. Chlorophyll is the compound responsible for this defect. StmcturaHy, chlorophyll is composed of a porphyrin ring system, in which magnesium is the central metal atom, and a phytol side chain which imparts a hydrophobic character to the stmcture. Conventional bleaching clays are not as effective for removal of chlorophylls as for red pigments, and specialized acid-activated adsorbents or carbon are required. 

Roy et al. (1991) extracted the pigments of green leafy vegetables in methanol-acetone-diethyl ether (1 1 1) the extracts were evaporated, reconstituted in the same solvent, and separated by TLC on silica gel G plates with a chloroform-petroleum ether-toluene-acetone (5 4 4 3) mobile phase. Pheophorbide b, mixed carotenoid, pheophorbide a, chlorophyll b, pheophytin b, chlorophyll a, pheophytin a, and carotene bands were obtained. This method can be used to detect artificial and natural colorants in food products. 

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