Colouring Matters of Australian Plants. X. Anthraquinones from Coelospermum Species

Abstract

The root-bark of two Coelospermum species is rich in colouring matter now shown to be a mixture of anthraquinones. In C. reticulatum they occur mostly in the free state. The principal constituent is a new natural anthraquinone, coelulatin, which has been identified as 1,3,8-trihydroxy-2-hydroxpethylanthraquinone Small amounts of rubiadin and lucidin have also been isolated. In C. paniculatum the anthraquinones occur mostly as glycosides which have been hydrolysed to a mixture of rubiadin, rubiadin-1-methyl ether, and lucidin. Nordamnacanthal is present in the free state, together with damnacanthol (isolated as the cyclic dimethyl ketal) and another new pigment which appears to be a dimethyl ether of coelulatin. Both plants apparently contain asperuloside but this could not be isolated.