When the leaves of most species of Aloe are cut a more or less copious exudate appears, yellow at first but rapidly darkening to brown or in a few species dark red. This exudate contains phenolic compounds which can be distinguished chromatographically as over 80 major zones staining characteristic colors with fast blue B, a dye reacting with phenols and coupling amines. Some of the compounds in these zones have been characterized. Most of the exudate compounds identified so far are chromone, anthraquinone or anthrone derivatives. Some are widespread in the genus, and some are confined to a few species and therefore of potential chemotaxonomic value.
These phenolics do not occur in the parenchyma cells within the leaf, where poly-saccharides and glycoproteins are characteristic. These substances are dealt with in other chapters, so are only summarised here.
Was this article helpful?