Recent investigations with synthetic flavylium salts (FVs) in
solutions of different nature (acetonitrile:water, ethanol, propilenglycol,
dioxane and 2-butanone) have shown that changes on colour
depend on the solvent and the FVs concentration (Ito, Tanaka,
Katsuki, & Fujii, 2002). In protic solvents the FVs exhibit red colouring,
whilst in aprotic solvents the solutions are yellow. This fact has
been explained by proposing that the red and yellow species correspond
to a monomer and dimer respectively; therefore, when
increasing FVs concentration, the red colouring is favoured.