Minaleshewa Atlabachew

Concentration Levels of Essential and Non-essential Metals in Ethiopian Khat (Catha edulis Forsk)

The levels of essential (Ca, Mg, Mn, Fe, Zn, Cr, Cu, and Co) and non-essential (Cd and Pb) metal in six different varieties of Ethiopian khat (Catha edulis Forsk, an evergreen stimulant plant) commonly consumed in the country and exported to the neighboring countries were determined by flame atomic absorption spectrometry. Known weight of oven-dried khat samples were wet-digested using 2xa0mL of (69–72%) HNO3 and 2xa0mL of (70%) HClO4 for 2xa0h and 30xa0min at variable temperature (120–270°C). The mineral contents in the digests were analyzed using flame atomic absorption spectrometer. The following concentrations ranges in fresh-weight basis were recorded in decreasing order: Ca (1,038–2,173xa0µg/g)u2009>u2009Mg (478.2–812.3xa0µg/g)u2009>u2009Fe (53.95–82.83xa0µg/g)u2009>u2009Zn (5.18–9.40xa0µg/g)u2009>u2009Mn (6.98–8.66xa0µg/g)u2009>u2009Cu (1.85–5.53xa0µg/g)u2009>u2009Cr (0.66–3.47xa0µg/g)u2009>u2009Co (0.41–0.80xa0µg/g). A wide variation in the mineral contents of khat from different region of Ethiopia was noticed. The toxic metals (Pb and Cd) were not detected in all the samples analyzed.

Simultaneous Determination of Alkaloids in Green Coffee Beans from Ethiopia: Chemometric Evaluation of Geographical Origin

The alkaloid compositions of 99 green coffee (Coffea arabica L.) bean samples comprising eight varieties (Harar, Jimma, Kaffa, Wollega, Sidama, Yirgachefe, Benishangul and Finoteselam) from the major production regions of Ethiopia were investigated. High performance liquid chromatography was applied for the simultaneous determination of four coffee alkaloids in the aqueous extracts of the beans. The limits of detection for the method were established as 13xa0mgxa0kg−1 for trigonelline, 7xa0mgxa0kg−1 for theobromine, 8.5xa0mgxa0kg−1 for caffeine and 4xa0mgxa0kg−1 for theophylline in the dry coffee beans. Theophylline was not detected in any of the samples. The determined concentrations (% w/w dry coffee beans) ranged from 0.98 to 1.32xa0% for trigonelline, 0.0048 to 0.0094xa0% for theobromine and 0.87 to 1.38xa0% for caffeine. The concentrations of the alkaloids varied significantly, depending on the geographical origin of the beans. Theobromine was not detected in coffee beans from the East (Harar coffees), and its absence in samples can be used to ascertain whether the coffee originates from this region. Coffee beans from the Northwest were characterized by higher concentrations of caffeine. Application of linear discriminant analysis provided 75xa0% correct classification of samples into the respective production regions, with a 74xa0% prediction success rate. The moderate classification efficiency obtained when using alkaloid data demonstrates the potential of using this class of compounds in discriminant models for determination of the geographical origin of green coffee beans from Ethiopia.

Matrix Solid-Phase Dispersion for the HPLC-DAD Determination of Psychoactive Phenylpropylamino Alkaloids from Khat (Catha edulis Forsk) Chewing Leaves

A fast and simple procedure based on matrix solid-phase dispersion was developed for the extraction of psychoactive phenylpropylamino alkaloids; cathinone, cathine and norephedrine, from khat (Catha edulis Forsk) chewing leaves, a stimulant and drug of abuse plant. Determination of the alkaloids was carried out by high performance liquid chromatography with diode array detection. Several extraction parameters, such as type of dispersant, type and volume of elution solvent and the ratio of sample to sorbent material were evaluated and optimized. Mean recoveries ranging from 89 to 92xa0% with relative SD of less than 6xa0% were obtained. A marked diversity in the phenylpropylamino alkaloid content and composition was found in seventeen different cultivars of Ethiopian khat. ANOVA results showed the existence of significant differences between the alkaloids profiles among samples of different varieties from different geographical locations in Ethiopia. The proposed method is simpler, faster and comparably more efficient than the frequently reported maceration followed by liquid–liquid extraction but as good and efficient as ultrasonic assisted extraction followed by solid-phase extraction.

A (-)-norephedrine-based molecularly imprinted polymer for the solid-phase extraction of psychoactive phenylpropylamino alkaloids from Khat (Catha edulis Vahl. Endl.) chewing leaves.

A molecularly imprinted polymer (MIP) was prepared using (-)-norephedrine as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker and chloroform as the porogen. The MIP was used as a selective sorbent in the molecularly imprinted solid-phase extraction (MIP-SPE) of the psychoactive phenylpropylamino alkaloids, norephedrine and its analogs, cathinone and cathine, from Khat (Catha edulis Vahl. Endl.) leaf extracts prior to HPLC-DAD analysis. The MIP was able to selectively extract the alkaloids from the aqueous extracts of Khat. Loading, washing and elution of the alkaloids bound to the MIP were evaluated under different conditions. The clean baseline of the Khat extract obtained after MIP-SPE confirmed that a selective and efficient sample clean-up was achieved. Good recoveries (90.0-107%) and precision (RSDs 2.3-3.2%) were obtained in the validation of the MIP-SPE-HPLC procedure. The content of the three alkaloids in Khat samples determined after treatment with MIP-SPE and a commercial Isolute C18 (EC) SPE cartridge were in good agreement. These findings indicate that MIP-SPE is a reliable method that can be used for sample pre-treatment for the determination of Khat alkaloids in plant extracts or similar matrices and could be applicable in pharmaceutical, forensic and biomedical laboratories. Copyright

Selected Secondary Metabolites and Antioxidant Activity of Khat (Catha edulis Forsk) Chewing Leaves Extract

Total phenolic, flavonoid, and tannin contents of 21 Ethiopian khat (Catha edulis Forsk) leaves and their related antioxidant activities were determined in the extracts of the young leaves, matured leaves, and tips of tender stem near the young shoots. A simplified, rapid, and robust method was also optimized for the analysis of total tannins using ovalbumin as a precipitating agent and Folin Denis reagent as the quantification technique. Among the solvents tested, aqueous mixtures of 70 and 80% acetone and 80% methanol provided higher phenolic compounds extraction efficiency than the corresponding pure solvents and other binary mixtures. Results of the analysis revealed that total phenols ranged from 129 to 274 mg tannic acid equivalent/g of dried young leaves and 89.3 to 175 mg tannic acid equivalent/g of dried tender stem tips. Total tannin content ranged between 70.2−153 mg tannic acid equivalent/g and 49.4−103 mg tannic acid equivalent/g of the dried young leaves and tips of tender stems, respectively. Similarly, total flavonoids concentration as catechin equivalent varied between 26 to 75 and 26 to 56 mg catechin equivalent/g of dried young leaves and tips of tender stems, respectively. Khat cultivars were found to pose a substantial antioxidative activity (as ascorbic acid equivalent) ranging between 173−290 and 118−211 mg ascorbic acid equivalent/g of dried young leaves and tips of tender stems near the young shoot, respectively. Matured leaves of khat accumulated a significantly lower concentration of secondary metabolites compared to the corresponding young leaves. This study reveals that khat leaves and tender stems accumulated a substantial amount of secondary metabolites, particularly tannins.

Isolation and in vitro permeation of phenylpropylamino alkaloids from Khat (Catha edulis) across oral and intestinal mucosal tissues

ETHNOPHARMACOLOGICAL RELEVANCEnKhat, the leaves of Catha edulis, is used as a natural amphetamine-like stimulant in eastern and southern Africa, as well as in the Arabian Peninsula. Leaves are masticated to elicit a state of euphoria. Although the psychostimulatory effects of the leaves are attributed to the presence of phenylpropylamino alkaloids (i.e. cathinone, cathine and norephedrine), the extent of permeation of these alkaloids across the oral and intestinal mucosa has not been established.nnnMATERIALS AND METHODSnCathinone was isolated in the form of the oxalate salt from young buds, following acid-base extraction. High performance countercurrent chromatography (HPCCC) was used to isolate cathine and norephedrine, following borohydride reduction of a mixture of the three alkaloids. The in vitro permeability of these three alkaloids in their pure form, as well as in a crude extract, was evaluated across Caco-2 cell monolayers and across excised porcine intestinal, sublingual and buccal tissues.nnnRESULTSnThe purities of the isolated cathine and norephedrine were in excess of 90%, thereby proving that HPCCC can be applied for efficient separation of these alkaloids from extracts of Khat. The apparent permeability (Papp) coefficients for the Khat alkaloids in their pure form were all above 1.0×10-6cm/s, indicating that the transport of the three alkaloids across the selected biological membranes is comparable to that of the highly permeable reference compound, caffeine. Although readily transported across the various membranes, the alkaloids were transported to a lesser extent when present in a leaf extract, suggesting that other phytochemicals present in the extract influence their permeation.nnnCONCLUSIONSnThese results provide evidence that chewing of Khat contributes to the buccal and sublingual absorption of the psychoactive alkaloids in the bloodstream directly across the oral mucosal membranes. In addition, it confirms that these metabolites will be readily absorbed from the gastrointestinal tract when swallowed.

Fluoride content of Ethiopian khat (Catha edulis Forsk) chewing leaves

The levels of water soluble and total fluoride concentration in 11 different varieties of Ethiopian khat (Catha edulis Forsk, an evergreen stimulant plant) commonly consumed in the country and exported to the neighboring countries were determined by fluoride ion-selective electrode. Known amounts of fresh khat samples were suspended in deionized water, stirred, and the supernatants exposed to a chelator that decomplexes fluoride were assayed. The total fluoride concentration in the leaves was also analyzed after the leaves were dried, charred, and ashed. Water soluble and total fluoride concentration in khat varieties varied, ranging from 0.19 to 0.43 µg g−1 fresh weight and 3.4 to 7.1 µg g−1 dry weight, respectively. The fluoride concentration in matured leaves (12 µg g−1) was higher than that in young leaves (6.5 µg g−1) dry weight. Assuming that daily khat leaves chewing for an adult is 100 g, fluoride intake from chewing leaves of the analyzed khat varieties is far below the daily fluoride tolerable upper limit. The safe intake of fluoride is recommended to be 1.5–4.0 mg day−1 for adults and less for children. However, chewing khat leaves may contribute a significant amount of fluoride for the total daily intake of an individual and should not be overlooked while estimating the total dietary intake of fluoride for individuals chewing khat leaves regularly.