A novel zwitterionic anthocyanin from evergreen blackberry (Rubus laciniatus Willd.)

A novel zwitterionic anthocyanin was isolated from evergreen blackberry (Rubus laciniatus Willd.) and structurally characterized as cyanidin 3-dioxalylglucoside. During short-term storage in acidified methanol, methyl esterification of the carboxyl group of the terminal oxalyl unit occurred, providing additional information for structural elucidation. Until now, oxalic acid as an acyl moiety of anthocyanins has been reported only in orchid flowers (Orchidaceae) but never in fruits or in the Rosaceae. This is the first report of an anthocyanin diacylated with oxalic acid, establishing a more widespread occurrence of anthocyanins substituted with aliphatic acids than hitherto believed.