) Pergamon 0305-1978(94)00095-6 BiochemicalSystemaB'cs and Ecology, Vol. 23, No. 3, pp. 267-275, 1995 Copyright(~ 1995Elsevier ScienceLtd Printed in GreatBritain. All rights reserved 0305-1978/95 $9.50+0.00 Chemotaxonomic Survey of Anthraquinones and Pre-anthraquinones in Roots of Aloe Species BEN-ERIK VAN WYK,* ABlY YENESEWt and ERMIAS DAGNEt *Department of Botany, Rand Afrikaans University, P.O. Box 524, Auckland Park, Johannesburg, 2006, South Africa; tDepartment of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia Key Word Index--Aloe; Alooideae; Asphodelaceae; roots; anthraquinones; pre-anthrequinones; chemo- taxonomy. Al~tract--Root samples from 172 species of Aloe were surveyed by TLC and HPLC for the presence of anthraquinones and pre-anthraquinones. With the exception of the three species of the series Serrulatae, 1,8- Dihydroxyanthraquinones (chrysophanol and asphodelin) were detected in all the species sampled. Compounds derived through the 1-methyl-8-hydroxyanthrequinone pathway, i.e. aloesaponarin I, aloe- saponarin II and laccaic acid o-methyl ester, together with their corresponding pre-anthraquinones were detected in 129 species. The results also s h o w that isoeleutherol is a useful chemotaxonomic character for the series Saponarieae. Introduction The leaves of Aloe species elaborate various phenolic compounds, including anthrone-C-glycosides, phenylpyrone derivatives and chromones (Reynolds, 1985). Due to their diversity and sporadic distribution, these compounds have so far been of limited taxonomic value. In a survey of 32 tropical African species of Aloe, the root constituents showed indications that they could be of chemotaxonomic value in the genus Aloe, especially at the supraspecific level (Dagne et al., 1994). The root compounds appear to be totally different from those of the leaves, and also seem more conservative. We have now examined the overall chemical pattern of the subterranean metabolism within the genus Aloe by surveying the roots of a large number of species chosen to represent all the major infrageneric groups. Materials and Methods Plant materials. Fresh root samples from 172 species of Aloe were collected from various sources as listed in Table 1, but mainly from the National Botanical Institute, Pretoria, South Africa. Voucher numbers or collecting localities are indicated in Table 1. Abbreviations are as follows: gardens of the National Botanical Institute at Pretoria (NBI), Kirstenbosch in Cape Town (NBG), Betty's Bay (HPBG), Nelspruit (LBG) and Worcester (KBG); Johannesburg Botanic Garden (JBG). Procedures. A microcomputer controlled liquid chromatographic system (Beckman Module 126) connected to a photodiode array detector (Beckman Module 168) monitoring at 275+ 35 nm (channel A) and 365+ 20 nm (channel B) was used. The samples were analysed with a Phenomenex Spherisorb 30DS 2 column (Cle reverse phase, 3 Ilm particle size, 100X4.6 mm i.d.; flow rate 1 ml min-1; 20 pl sample loop). The solvent system comprised a 10-100% non-linear gradient of A in B. A: MeCN; B: MeCN/H20; 45:55 (R t values: 1 = 12.2; 2 = 5.12; 3 = 3.27; 4= 7.45; 5 = 7.96; 6= 4.86; 7 and 8= 2.63; 9= 5.14). Compounds with similar R t values easily separate in the TLC systems described below. Fresh roots were rapidly air-dried. The powdered roots (ca 1 g) were extracted by cold percolation in acetone for 12 h. After removal of the solvent, the crude extracts were taken up in MeCN and passed through C~ cartridges to remove substances of high R r Samples were dissolved in a MeCN/H20 (1:1) mixture and injected into the HPLC system. The crude extracts were also analysed by TLC using the following solvent systems: CHCIz/petrol (1:1), CHCla/EtOAc (1:1) and benzene/petrol/EtOAc (1:2:1) on silica gel (Merck) plates. Chromatographic zones were detected under UV light (254 and 366 nm). Identification of compounds was (Received 20 May 1994) 267