Anthocyanins

  • Basic structure
  • Pelargonidin Pg... R1 = H, R2 = H violet-red
  • Cyanidin Cy... R1 = H, R2 = OH purple
  • Delfinidin Dp... R1 = OH, R2 = OH blue-violet
  • Peonidin Pn... R1 = H, R2 = OCH3 violet
  • Petunidin Pt... R1 = OH, R2 = OCH3 dark red
  • Malvidin Mv... R1 = OCH3, R2 = OCH3 blue-violet
  • Carbohydrates: Glu, Gal, Xyl, Ara, Rha, always C-3, often C-3 and C-5, rarely C-7
  • Acids: p-coumaric, caffeic, ferulic

Examples:

  • Cyanidin-3-O-β-D-glucoside (generally known)
  • (E)-petunidin-3-O-[6-O-(4-O-p-kumaroyl-α-L-rhamnopyranosyl)-β-D-glukopyranosid]-5-O-β-D-glukopyranosid
    • Trivially: petanin (red potato variety)

Anthocyanins of fruits and vegetables

  • Dependence of coloration on various factors:
    • pH of the environment;
    • Copigmentation, or transformation to other dyes;
    • sulphur dioxide;
    • hydrogen peroxide

pH of the medium

  • Copigmentation
    • Interaction with procyanidins (e.g. catechins, so-called copigments) → colour complex.
  • Transformation to other dyes, colour complex → dimer (oligomer), insoluble condensation products, sediments phlobaphenes.
  • Sulphur dioxide → colourless sulphonic acids.
  • Hydrogen peroxide → colourless products.


References