Question

• Some anthocyanins have sugar molecules attached to both the 3 and 5 position. These molecules are called diglycosides. Assuming that sugar increases the polarity (hydrophilicity) of the anthocyanin molecule, would a diglycoside migrate further or less than a monoglycoside on TLC?

Answer 1

1. Anthocyanins are the flavonoids belonging to the class of polyphenols which are responsible for the coloration of fruits, vegetables, etc. They are also considered to be powerful natural antioxidants.

2. Most common sugars are found to be linked to C3, C5, and C7 ( where C represents carbon)

3. When sugar moiety is attached to the flavonoids, it is called glycoside, depending on the no. monoglycosides, diglycosides...

4. Assuming that the addition of diglycosides (two sugar moieties) to flavonoids increases its polarity than the addition of monoglycoside (single sugar moiety), the thin layer chromatography will show that the diglycoside added molecule will travel slower relative to the monoglycoside added anthocyanin.

5. Reasoning: The TLC has two phases, one stationary ( mostly composed of silica gel ) which is polar and another mobile phase (composed of solvent in a certain ratio ) which are non-polar or less polar. The principle of TLC works on the difference in solubilities and adsorption to the two phases. The more polar molecule I.e diglycoside anthocyanin will now show a higher affinity towards the polar silica gel which is a stationary phase and have less interaction with the mobile phase. Whereas the less-polar monoglycoside anthocyanin will interact with the mobile phase and travel faster relative to the polar one. Therefore, the diglycoside anthocyanin will travel with less speed relative to the monoglycoside anthocyanin. he relative speed depends upon the different solubilities and adsorption to the two phases.

Thus, a monoglycoside will migrate more further than the diglycoside.

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