4082-08-0Relevant articles and documents
A simple synthesis of 3-deoxyanthocyanidins and their O-glucosides
Al Bittar, Sheiraz,Mora, Nathalie,Loonis, Michèle,Dangles, Olivier
, p. 4294 - 4302 (2016/07/06)
This work deals with the chemical synthesis of simple analogs of anthocyanins, the main class of water-soluble natural pigments. Flavylium ions with hydroxyl, methoxyl and β-D-glucopyranosyloxyl substituents at positions 4′ and 7 have been prepared by straightforward chemical procedures. Moreover, the two 3-deoxyanthocyanidins of red sorghum apigeninidin (4′,5,7-trihydroxyflavylium) and luteolinidin (3′,4′,5,7-tetrahydroxyflavylium) were synthesized in a one-step protocol. Attempts to synthesize luteolinidin O-β-D-glucosides resulted in a mixture of the 5-O- and 7-O-regioisomers in low yield. A preliminary study of the 4′-β-D-glucopyranosyloxy-7-hydroxyflavylium and 7-β-D-glucopyranosyloxy-4′-hydroxy-flavylium ions shows that simply changing the glucosidation site can profoundly affect the color intensity and stability.
Chemistryl of Anthocyanin Pigments. 9. UV-Visible Spectrophotometric determination of the Acidity Constants of Apigeninidin and Three Related 3-Deoxyflavinium Salts
Brouillard, R.,Iacobucci, G. A.,Sweeny, J. G.
, p. 7585 - 7590 (2007/10/02)
The equilibrium constants for the structural transformations of some 3-deoxyanthocyanidins in water at 25 deg C have been measured by using the pH-jump method.This method have been described previously.According to their particular substitution patterns, hydroxylated flavinium salts can exist in slightly acidic media in several neutral forms: the quinoidal bases A, the carbinol pseudobase B, and the chalcone pseudobase C.Two of the conpounds investigated, namely 4',5,7-trihydroxyflavinium (apigeninidin) and 4'-methoxy-4-methyl-5,7-dihydroxyflavinium chlorides, exist essentially as a mixture of the three neutral forms A, B, and C, the colored species A being the most abundant.As expected, 4',7-dihydroxyflavinium chloride is stable in the open chalcone structiure C.This result is in a good agreement with the catalytic light effect generally observed for the ring-closure reaction of this species leading to the flavinium cation AH+.Only the monohydroxylated pigment 4'-methoxy-4-methyl-7-hydroxyflavinium chloride is the quinoidal base A perfectly stable, whatever the pH.In contrast to natural anthocyanins, the hydration of the pyrilium ring is less efficient and occurs, therefore, at much higher pH values (pH 5-6).Proton loss from the phenolic acidic hydroxyl groups of the flavinium cation takes place in the usual acidity range (pH 4-5), indicating that these groups are strongly hydrogen bonded to the surrounding water molecules.The chalcone content is much higher than for the anthocyanins, and for 4',7-dihydroxyflavinium chloride for instance, the value for the equilibrium ratio of the chalcone to the carbinol is as high as 20.6.
Identification of three hydroxyflavan phytoalexins from daffodil bulbs
Coxon, David T.,O'Neill, Timothy M.,Mansfield, John W.,Porter, Alexander E.A.
, p. 889 - 891 (2007/10/02)
Three phytoalexins were isolated from daffodil bulb scales inoculated with Botrytis cinerea and identified as 7-hydroxyflavan, 7,4′-dihydroxyflavan and 7,4′-dihydroxy-8-methylflavan. The structures of the phytoalexins were confirmed by total synthesis.
