Development of Free Radical Products during the Greening Reaction of Caffeic Acid Esters (or Chlorogenic Acid) and a Primary Amino Compound
ESR spectra were measured directly on a marked greening reaction mixture of Et-caffeate and a primary amino compound in alkali solution under aeration. A clear hyperfine structure was commonly detected early in the greening reaction with different amino compounds. Its hyperfine spectrum split into seven peaks was analyzed and found to be due to the oxidized free radical product of the Et-caffeate using an authentic sample system. Another type of hyperfine ESR spectrum was observed later in the reaction, and was altered with different amino compounds. The hyperfine structure for n-butylamine split into 12 lines. The latter type of free radical products were assumed to be a semiquinone type radical compounds of the trihydroxy benzacridine derivative, which was identified as the principal structure of the green and yellow pigments formed by this greening reaction system. A formation mechanism of the green pigment and related products involving these free radical products is proposed.
Structure of Green Pigment Formed by the Reaction of Caffeic Acid Esters (or Chlorogenic acid) with a Primary Amino Compound
A marked greening observed in some foods such as sweet potato, burdock, and others during food processing was shown to be due to green pigment formation by the condensation reaction of two molecules of chlorogenic acid or caffeic acid ester with one molecule of a primary amino compound under aeration in alkaline solution. Reduction of the green pigment by ascorbic acid or NaBH4 gave a yellow product, which readily turn green and then blue in air. The reduced and acetylated product of the green pigment was identified to be a novel trihydroxy benzacridine derivative, and the yellowish ethanol solution of this product immediately turned green upon addition of butyl amine or diluted alkali. Therefore, the green pigment was assumed to be an oxidized quinone type product of trihydroxy benzacridine. This identification of the structure was supported by the correspondence of the measured absorption spectra with those calculated by the molecular orbital method. A possible charge transfer complex between products of different oxidation steps in green solution was proposed.
Oxyzimtalkohole und ihre Dehydrierungs‐polymerisate
Fur die Bereitung des Coniferyl- und Sinapinalkohols werden verbesserte Vorschriften gegeben Die Dehydrierungs-polymerisation des Coniferylalkohols kann bei einer kristallinen dimeren Stufe dem Dehydro-diconiferylalkohol, festgehalten werden. Seine Konstitution wurde bestimmt. Durch weitere Dehydrierung verwandelt er sich in ligninartige Produkte. Auser der Pilzredoxase kann fur die Bereitung des Dehydro-diconiferylalkohols auch das Redoxasesystem des in Verholzung begriffenen Gewebes verwendet werden. Es ist daher nicht zu bezweifeln, das diese Substanz ein wesentliches Bauelement des naturlichen Lignins ist.