Browsing by Author "Alemu Melaku"

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    Comparative Chemical Studies on the Leaves of Sarto Aloe Species of Ethiopia
    (Addis Ababa Universty, 1990-06) Alemu Melaku; Dagne Ermias (PhD)
    Chemical investigations on the leaves of A. berhana Reynolds, A. rivae Oaker, A. megalacantha Baker and A. pulcherdma ined. resulted in the isolation of a total of nine compounds, the structures of which were established by spectroscopic means as well as chemical degradation to known compounds and compaidLson, in some cases, with authentic samples. Chrysophanol and P -Sitosterol were isolated from all four species. Furthermore, A. berhana afforded a novel pre-anthraquinone (tentatively given the trivial name berhanone), protocatechuic acid (a biologically important aromatic acid rare from a natural source), barbaloin (the major active constituent of the officially recognised commercial aloes responsible for the- use of the plant as purgative) and aloe-emodin. A. rivae and A. megalacantha yielded aloe-emodin, berhanone, barbaloin and aloinoside (a constituent of the commercially important Cape and Socotrine aloes). A. pulcherima afforded nataloin (major constituent of the commercial Natal aloes) add 7-hydroxybarbaloin (the characteristic substance of the commercially important Curacao aloes in the European Pharmacopoeia). A further comparative chemical screening on the presence of the commercially important compound, barbaloin, in the loaves of some Aloe species by means of HPLC and TLC analyses revealed that this glucoside is the major constituent of A, berhana Reynolds, A. rivae Baker, A. megalacantha Baker, A* calidophylla Reynolds, /\. secundiflore Engler, A. mcloughlinii Christian, and A. otalensis Baker, Barbaloin was, however, not detected in the leaves of A. pulcherimn.