Tetrahydroanthracenes as Markers for Subterranean Anthranoid Metabolism in Aloe Species

Summary Anthranoids in the roots of 14 Aloe species were surveyed by a novel high-performance liquid chromatographic method and photodiode-array detection and, in leaves of the same species, by thin-layer chromatography. Whereas diastereomeric anthrone-C-glycosyls were detectable in the majority of leaf samples, these compounds as well as anthrone aglycones were shown to be absent in root material. The anthraquinone aglycone chrysophanol was found in every root extract. Roots of ten species contained the tetrahydroanthracene aglycone aloesaponol I, which was isolated as a major anthranoid from root and rhizome material of A. succotrina Lam. Three of the remaining four species exhibited compounds with UV-VIS spectra analogous to aloesaponols III/IV. The substitution pattern of the compounds detected indicates striking differences between subterranean and aerial anthranoid biosynthesis in Aloe . With regard to distribution and accumulation of tetrahydroanthracenes within the individual plant as well as in the species examined here, these anthranoids are suggested to be specific markers for subterranean Aloe metabolism.