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Paper | Special issue | Vol 97, No. 2, 2018, pp.946-959
Published online, 10th April, 2018
DOI: 10.3987/COM-18-S(T)74
The First Synthesis of 3-O-Methylcyanidin and the Effect of 3-O-Substitution on Stability Under Acidic Conditions

Asmaa B. El-Meligy, Takehiro Ishihara, Kin-ichi Oyama, Ahmed M. El-Nahas, and Kumi Yoshida*

*Graduate School of Informatics, Nagoya University, Chikusa, Nagoya 464-8601, Japan

Abstract

The simplest and most common anthocyanin in nature is 3-O-glucosylcyanidin (1), and 3-O-glucosylation is believed to stabilize the chromophore. To clarify the effect of the glucose residue we compared the stability of 1 with its aglycone, cyanidin (2), and newly synthesized 3-O-methylcyanidin (3). In an aqueous solution at pH 1, 1 and 3 showed similar stabilities, and 2 was less stable than 1 and 3, indicating that 3-O-substituion does enhance stability. We also analyzed the co-pigmentation effect of flavocommelin (4) and rutin (5), on the color and stability of 3-O-substituted cyanidins and cyanidin. The bathochromic shift of λvismax and stability of the color by addition of 4 was greater than that of rutin (5). 4 might stack closer and stronger to the anthocyanidin chromophore than 5.