Cyanidin 3-Oxalylglucoside in Orchids

In the last few years increasing evidence has been presented that acylated flavonoids are widespread in higher plants [1—3], Besides the well known phenolic acids (hydroxybenzoates, hydroxycinnamates), aliphatic acids have only recently been extensively detected as acyl moieties of anthocyanins or gly­ cosides of (iso)flavones and flavonols. To date, ace­ tic, butyric, malonic, 2-methylbutyric, succinic and tiglic acids have been identified, among which malonic acid appears to be the most commonly oc­ curring one. As a consequence of the great lability of aliphatic acid esters, such natural products might have been frequently overlooked in earlier studies [3, 4], Although there is only fragmentary knowledge of orchid anthocyanins [5], it is known that complex mixtures of acylated and non-acylated anthocyanins cause a broad spectrum of orchid flower colouration. In a survey of European orchids, Uphoff [6] de­ scribed the widespread occurrence of cyanidin 3monoglucoside, 3-diglucoside and 3,5-diglucoside together with complex acylated anthocyanins, the nature of which needed further investigation. As first part of a comprehensive investigation of phenylpropanoids in flowers of European orchids, we report here on one of their major acylated antho-