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

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.