Eiochemicsl CQsCm.siics andEcology. Vol. 24. No. 4, pp. 347-362,1996 Pergamon Cofqight Q 1996 Elsevier Science Ltd Printed in Great Sdtain. All rights resewed 0305-1978/96 S15.00+0.00 PII: SO306-1878(88)OOOl2-8 Chemotaxonomy of Aloe turkanensis and Aloe scabrifoha from Kenya T REYNOLDS Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, U.K. Key Word Index-Aloe turkanensis;Aloe scabrtYolia; Kenya; leaf exudates; phenolics; HPLC; chemical taxonomy. Abstract-Phenolic leaf exudate constituents from Aloe turkanensis and A. scabrifolia were examined by TLC and HPLC. The chromatographic patterns clearly differentiated between the two species, which had originally been described as one, although geographically separated. Some of the chromatographic zones could be equated with known compounds, but others were characterized only by their colour reaction and UV absorption values. Comparisons were made with chromatographic patterns of other Aloe species. Copyright 0 1996 Elsevier Science Ltd. Introduction During a chromatographic survey of phenolics in leaf exudates from Aloe species in the R.B.G., Kew collection using two-dimensional TLC, it was noticed that dif- ferent individual plants accessioned as Aloe turkanensis Christian gave two, quite different, chromatographic patterns related to their collection sites. Subsequently some of the plants originally grouped under this name were demonstrated else- where to be taxonomically distinct as a new species, A. scabrfo/ia Newton et Lavranos, on the basis of habit, leaf surface, inflorescence, shape and floral details as well as geographical location (Newton and Lavranos, 1990). This paper describes details of the chromatographic separation by TLC and HPLC, of known and unknown phenolic compounds from the leaf exudates of a number of indi- viduals from both species collected at specified locations. Materials and Methods Exudates were obtained by cutting segments from leaves of approximately the same age from Aloe plants in the R.B.G., Kew collection and leaving them to stand in methanol for 2 h. The solutions were separated by filtration, concentrated by evaporation in VJCUO and applied directly to TLC plates or to an HPLC column. Chromatographic separations were carried out as described previously (Reynolds, 1994). Results and Discussion Figure 1 shows two-dimensional TLCs of constituents of leaf exudates reacting with Fast Blue 9, from individuals from the Kew collection attributed to Aloe tur- kanensis and A. scabrifo/ia together with the HPLC profiles of compounds absorbing at 300 nm. Table 1 shows the fluorescence of the TLC zones at 350 nm after fuming with ammonia and the UV absorption data of the distinct HPLC peaks. In some instances these zones and peaks can be equated to each other and sometimes identified as known compounds. The relative absorption of UV light at 300 nm by the HPLC peaks is also shown and the intensity of the stained TLC zones shown on an arbitrary visual scale. Both species contain barbaloin while A. scabrifolia also contains other barbaloin (Received 9 October 1995; accepted 12 January 1996) 347