Greening pigments produced by the reaction of ethyl caffeate with methylamine.

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Abstract
Little is known about the greening reaction of chlorogenic acid with amino acid in alkaline conditions. The isolation and characterization of the pigment were attempted by using ethyl caffeate and methylamine instead of chlorogenic acid and amino acid. The green compounds were purified by using Sephadex G-10 and TLC, and were analyzed by ESR and 13C NMR. The ESR spectrum of F3 (corresponding to purified pigment) in a liquid state showed that the structure of the C-OH moiety seemed to give the quinone type or its polymerized form. The ESR spectrum of F3 in a solid state showed that the g-value of this fraction was 2.003. On the basis of the 13C NMR spectrum, the signals assigned to 2 carbons (C-1" and C-2") of the alcohol moiety of ethyl caffeate were observed clearly in F3. Considering the chemical shift of C-1 in ethyl caffeate, the C-1 in F3 could exist as .**GRAPHIC**. F3 seemed to be a precursor of the greening compound.

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