The phenolic constituents of plants and their taxonomic significance: II. Monocotyledons

Abstract

The phenolic constituents of the monocotyledons are generally similar to those of the dicotyledons. Ellagic acid is, however, absent and the other ‘regular’ trihydroxy-substituted constituents myricetin and leucodelphinidin are only rarely present. Leucocyanidin is also relatively uncommon. The tendency evident in the dicotyledons for leuco-anthocyanins and flavonols to be less frequently, and navones and methoxy-substituted aromatic acids to be more frequently present in herbaceous than in woody plants is supported by the present data. Glycoflavones, i.e. navones carbon-carbon substituted with glycosyl residues, occur more frequently than in the dicotyledons, especially in the Gramineae, Iridaceae and Liliaceae. In the Iridaceae the glycoxanthone mangiferin is also frequently present. In the last family, the genera Crocus and Iris have been examined in detail. In Iris, where there is considerable morphological diversity, the chemical data support the recognized division of the genus on morphological grounds. In Crocus, where the division of the genus is less clear-cut, there is corresponding difficulty in ascertaining distinctions on chemical grounds. The bearing of the chemical evidence on possible phylogenetio relationships within the monocotyledons, and as between the monocotyledons and the dicotyledons is discussed.