EXTRACTION AND IDENTIFICATION OF CAROTENOIDS IN GREEN EATABLE VEGETABLES – A PROPOSAL FOR PRACTICAL CLASSES

Abstract

The carotenoids are natural colored pigments varying from yellow to red. They are divided in carotenes, as β-carotene and lycopene, and their oxygenated derivatives, the xanthophylls, as astaxanthin present in shellfishes. β-carotenes are precursors of vitamin A being an important anti-oxidant molecule. Both β-carotene and lycopene, have been used in the cancer inhibition. In the present work, we detected the presence of carotenoids using thin layer chromatography (TLC) for the separation of the pigments of green eatable vegetables, aiming the application of those methods in the practical classes of the Biological Science Course of UFPE. Spinacia oleracea (spinach), Brassica oleracea (cabbage) and Lactuca sativa (lettuce) were macerated with washed send in the presence of sodium sulfate followed by the addition of 25 ml of hexane until total homogeneity. The extracts were filtrated, washed with 10 ml of hexane, concentrated in vacuum evaporator and resuspended in hexane. The hexanic extract was applied on silica gel G plates activated at 120°C for 30 min. The chromatogram was developed in hexane-benzene-pyridine system (40:5:5). All the used solvents were from analytical grade, β-carotene (C40H56) and astaxanthin (C40H52O4) from Sigma St. Louis – USA were used as standards. Meanwhile, the lycopene was identified by a comparison with the same compound present in a tomato extract. The results demonstrated that β-carotene has a higher concentration in the spinach and cabbage than in the lettuce. However, lettuce presented more lycopene than the others two vegetables. Astaxanthin was not detected in all studied vegetables. In conclusion, green eatable vegetables could be a good source of β-carotene protecting against low vitamin A concentration in the organisms and the degenerative disturbs related to oxidative reactions. Finally, the students will be orientated to correlate the carotenoids actions in the prevention of diseases caused by free radicals.