The Rapid Isolation of Carotenoids from Foods
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The isolation and chromatoeraohic senamtion of carotene and lvconene is s oooular oresnie .. ~"~ Laboratorv , exoeriment. Present methods for usnmnoid i x h h m from foods such ns strained mrrurs nnd tomaro pwre involve a time consuming dehydration with boiling erhanul folluwrd by rxtracthm with hot mrthylene chlorrde.' Similarly, ramuno~drxrractiun from citrus peel requires a preliminary grinding of the peel with sand to rupture the oil cells.2 We have determined that, with carrots and tomato paste, both the dehydration and the extraction can be accomplished without heating the organic solvents. This modification saves time, requires less equipment, is less hazardous and results in minimal earotenoid decomposition. In the case of citrus peel samples, we have found that the tedious and messy grinding with sand can be eliminated by the use of SEP-PAKTMSilica C a ~ t r i d wa. mini-chromatoeraohie ~ column which isolates and "traee-enriches" the csrotenaids in quantities sufficient for subseqient thin-layer and open column chromatographic analysis. Finally we have replaced the commonly used but toxic benzene tlc developing solution4 with a mixture of methylene chloride: hexane. Isolation of Carotenoids from Tomato Paste and Strained Carrots. Place 5-log of "food" in a small beaker, add 10 ml of 95% ethanol, stir thoroughly for 1min, either decant or filter through a small piece of glass wool pressing as much liquid as possible from the paste. Discard the liquid which contains alcohol, water, and some soluble salts. Place the "dehydrated" paste in a clean beaker, add 5-10 ml of methylene chloride, stir thoroughly, decant or filter the orange solution and carefully evaporate to about 1ml. The extracts are then chromatographed according to existing procedures. For tlc analysis, a developing solution of methylene ch1oride:hexane (3:10) separates the mixture into a minimum of three colored comqonents: lycopene, xanthophylls and &carotene withRr values of 0.4,0.5, and 0.6, respectively. Isolation of Carotenaids from CitrusFruit Skins. Cut approximately 1gof orange, lemon, or grapefruit peel intovery small pieces, place in a mortar and grind, adding 3-5 ml of hexane during the grinding. Decant or filter the solution through a small piece of glass wool. Repeat the procedure and then flush the combined 5-10 ml of yellow extracts onto a SEP-PAK Silica Cartridge that has been previously pre-wetted with h e m e . Flush the cartridge with 3 4 ml of hexane and elute the earotenoids with 1-2 ml of methylene chloride, ealleeting only the colored eluate. Evaporate to approximately 0.5 ml and chromatograph by previously described procedures. The SEP-PAK effectively "trace enriches" the small quhntities of earotenoids onto the silica packing making unnecessary the more efficient hut tedious grinding with sand. Additional infdrmation on this separation will be supplied upon request. ~
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Pavia, D. L., Lampman, G. M., and Kriz, G. S., "Introduction toOrganicLahoratory Techniques," W. B. Saunders Co., Philadelphia, 1976. p. 78-83, Moore, J. A,, and Dalrymple, D. L., "Experimental Methods in Organic Chemistry," 2nd Ed., W. B. Saunders Co.,, Philadelphia, 1976, p. 218-225. 31nformation on use of SEP-PAK Cartridges may he obtained from Waters Associates, 34 Maple Street, Milford, MA "l"F? "L,",.
Gortler, L. B., and Tripp, R. C., "Techniques and Experiments in Organic Chemistry," 2nd Ed. Avery Publishing Group, Ine., Wayne, N.J., 1977,p. 5G59. Presently on Sabbatical Leave a t Waters Associates, Milford, MA.
St. Joseph College West Hartford, CT 06117
676 1 Journal of Chemical Education
Harold T. MeKoneS
