The Bitter Constituent of Gesho ( Rhamnus Prinoides ) Leaves
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Date
1994-06
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Addis Ababa Universty
Abstract
Gesho, Rhamnus prinoides L’Herit (Rhamnaceae) is a shrub or tree which can be
up to 6 m tall. It is cultivated in Ethiopia for use as an ingredient in the making of the
home brewed drinks-Telia and Tej.
Phytochemical investigations of the leaves of this plant resulted in the isolation and
characterization of the bitter prinicple- a naphthaenic lactone glucoside named geshoidin,
in addition to three anthraquinones, a pre-anthraquinone and a flavonol. These compounds
are chrysophanol (1), physcion (2), musizin (19), emodin (3), rhamnocitrin (40) and /3-
sorigenin-8-0-/3-D-glucoside (68). Acetylated and methylated derivatives as well as
hydrolysis products of the glucoside and the permethylated compound are also
characterized. These include|6-sorigenin-8-0-/3-D-glucoside-peracetate(69), /3-sorigenin-8-
0-/3-D-glucoside-permethylate (70) , /3-sorigenin (22) and /3-sorigenin-l -methylether (71),
respectively. Compounds 2 and 3 have been isolated previously from the fruits of R.
prinoides. 19 and 40 have not been reported from this plant while 68 is a novel natural
product ,
Based on spectroscopic data, two possible explanations are offered for the upfield
chemical shift of the peri hydroxyl proton in 68. A sensory panel concluded that compound
68 is a bitter principle in the leaves of Gesho. At least 1% of the dry leaves of Gesho
contain this bitter component
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Keywords
Rhamnus prinoides