Question

For the isolation of lycopene from tomato paste, the paste was washed with hexanes, potassium carbonate and sodium chloride, drained aqueous layer, dried with magnesium sulfate, filtered and rotovaped. The extract was then subject to column chromatography using hexanes and alumina. eventually 10% acetone in hexanes was introduced. The beta carotene yellow band was then separated and developed in a thin layer chromatography chamber using 1% acetone in hexane, and the spot for beta carotene was not seen. Why?

Answer 1

Lycopene from tomato paste

1) chemical extraction is a process by which a specific compound is isolated from a mixture of compounds by used of a chemical pricess usaually by the addition of a solvent in which the desired compound has enhanced solubility.

2) Some of the trans-lycopene isomerizes during the process which is evident by slight loss of color of the pigment thus isolated.

Cis-lycopene does not have bright color as trans-lycopene. This is seen by broad absorption bond in the UV spectrum.

4) Using column chromatography with alumina as the support. Alumina is acidic.

When more polar solvent as ethylacetate is poured in excess, the more polar compoenent would readily comes out of the column from the mixture.

Whereas, when less polar hexane is poured in excess as the mobile phase, less polar compoenent of the mixture comes out of the column.