A New Class of Flavone Pigments in the Palmae

In the course of a chemotaxonomic flavonoid survey of monocotyledonous families related to the grasses attention was turned to flavonoids in leaves of the Palmae. Many of the flavonoids present were readily identified as known pigments2. Thus, the flavonols, kaempferol and quercetin, and the flavones, apigenin and luteolin, were variously detected in glycosidic combination. Glycosylflavones based on apigenin and luteolin were also present. In one case, Chamaerops humilis, the rare flavone tricin, already known as a grass constituent, was found 2. In addition, a series of apparently novel flavones were present; besides being very water-soluble, these pigments had markedly different chromatographic behaviour (very high R/s in water, very low Rfs in butanol-acetic acid on paper) from the commoner constituents. An important clue to their identity came when it was discovered they were electrophoretically mobile in acid buffer (pH 2.2), carrying negative charges. The only charged flavonoids known are the anthocyanin pigment cations and the rare anionic flavonol, persicarin, the 3-potassium bisulphate of isorhamnetin. Persicarin was first found some years ago in several Polygonum species (Polygonaceae) 3 ' 4 and in Oenanthe stolonifera (Umbelliferae) 4 and more recently closely similar substances have been reported in two Lasthenia species (Compositae) 5. Further studies have now revealed that the flavones present in the palms occur, like the flavonol persicarin, in conjugation with potassium bisulphate and thus they represent the first members of a new class of flavone pigments.