The families Caryophyllaceae and Molluginaceae contain anthocyanins, but not betalains. To date, no plant is known to have both types of pigments. The uv-visible spectra of betalains and anthocyanins are quite similar and in plants that have them, the betalains serve much the same role in pollination and seed and fruit dissemination. Imidazole Alkaloids Imidazole alkaloids are found in several families, but are probably best known from the genus Pilocarpus of the Rutaceae. Pilocarpine, derived from histidine, is a peripheral stimulant of the parasympathetic system and is used as a myotic to counteract the mydriatic effects of atropine and other parasympatholytic drugs.
Pilocarpine is used in the treatment of glaucoma.
Other imidazole alkaloids are known from Alchornea , Euphorbiaceae, and a variety of other plants. Because of the diverse taxonomic sources and the variation in struction, these may not represent a homologous series of alkaloids. About 45 alkaloids of this series are known. Several have pronounced antitumor activity, but are too toxic for practical use. They interact at the same binding sites as vincristine.