Flavonoid patterns in leaves of the gramineae

Abstract

In a leaf survey of 274 species from 121 genera of the Gramineae, flavone C-glycosides and tricin were found to be the major flavonoids in 93% of the samples. By contrast, apigenin and luteolin O-glycosides were comparatively rare, as were the flavonols, kaempferol and quercetin. In only one species, Rottboellia exaltata were flavonols the sole flavonoids. 7.3′.4′-Trihydroxyflavone, which has been detected in the Juncaceae, was found in 3 of 5 samples of the species Bothriochloa bladhii. Flavonoid sulphates were present in 16% of the species examined. While in most of these plants tricin glycosides were conjugated with sulphate, in Paspalum convexum quercetin mono- and di-sulphates and 1-caffeylglucose sulphate were identified. Flavonoid sulphates are present in the tropical-subtropical subfamilies: Panicoideae (in 18% of species). Chloridoideae (15%) and Arundinoideae (40%) but were not found at all in tribes of the cool temperate regions. Proanthocyanidins were found in only 3% of the species surveyed. The flavan-4-ol, luteoforol and its apigenin analogue were detected only in the subfamilies Panicoideae and Chloridoideae, where they occured in 12 and 6% of species respectively.