Levels of major, minor and toxic metals in tubers and flour of Dioscorea abyssinicagrown in Ethiopia

Dioscorea abyssinica, commonly known as yam, is an indigenous plant in Ethiopia. Its root tuber is used as staple and co-staple food in South Nation Nationality People and Regional State of Ethiopia. This study was carried out to analyze the selected mineral nutrients in the tuber and flour of D. abyssinica grown in different parts of the country for human consumption. Samples collected from five different areas were analyzed for eleven metals (Ca, Mg, Fe, Zn, Cu, Mn, Co, Cr Ni, Cd and Pb) by flame atomic absorption spectrometry and two metals (K and Na) by flame emission spectrometry. Known weight of oven-dried sample was  wet-digested using 3 mL of (69–72%) HNO3 and 1 mL of (70%) HClO4, for 2 h at variable temperature (120–270 oC). The validity of the optimized procedure was evaluated by the analysis of spiked samples whose recovery was in the range of 92–105%. The mean concentration range (in ìg/g) of each metal in D. abyssinica samples were K (8,469–13,914), Na (133–405), Ca (172–448), Mg (180–354), Fe (28.3–144.5), Mn (12.0–14.5), Zn (12.3–44.5), Cu (7.26–17.6), Co (1.91–8.68), Cr (0.86–3.41) and Ni (2.43–5.31). D.abyssinica could be good sources of essential trace metals to the individuals, more particularly Fe and Zn were higher than the entire trace metals in the samples investigated while Cd and Pb were in minor quantities and hence the plant is free from toxic heavy metals. Consuming 100 g of this tuber per day contribute the following concentration range of Fe, Zn, Cu, Mn, Co, Ni and Cr in mg/100 g per day: 2.8–14.4, 1.2–4.5, 0.73–1.8, ND–1.5, ND–0.87, 0.24–0.53 and 0.09–0.34 mg/100 g,respectively. Statistical analysis revealed that significant variations in metal concentrations among the sampling sites were observed for some of the metals when pair wise test was made while insignificant variation were seen for the remaining metals. D. abyssinica could be a better source of K, Ca, Fe and Zn to human compared to the common cereal flours (barley, wheat and red teff flour) as well as tuber food products like potato, cassava, yam, and enset (Ensete ventricosum), while it could be an alternative source of the other essential mineral nutrients to the individual daily mineral intake.Key words: Root tuber, Dioscorea abyssinica, metals, Ethiopi

Cation-exchange solid-phase and liquid-liquid extraction for the determination of khat alkaloids by reversed phase HPLC-DAD

Leaves of khat (Catha edulis) are masticated to elicit their psycho-stimulating properties, resulting from the presence of the phenylpropylamino alkaloids. The determination of these alkaloids is important in pharmacological, phytochemical, forensic and law enforcement environments. In this study, the use of strong cation exchange-solid phase extraction (SCX-SPE) was investigated as an alternative means of sample purification prior to the determination of cathinone, cathine and norephedrine by reversed phase (C18) high performance liquid chromatography (HPLC). Extraction parameters for SCX, including loading capacity and washing solvents, were established. An existing liquid-liquid extraction (LLE) method was improved in terms of recoveries obtained, by using ethyl acetate as extractant. For pure standards of the khat alkaloids, recoveries ranged from 83 to 97%. Preconcentration, using a Genevac evaporator after the addition of acidified water to the sample, restricted analyte losses when compared to concentration under nitrogen. Although comparable recoveries were obtained when preconcentration was achieved in the presence of acidified water by rotary evaporation, this method is not suitable for large sample numbers. Best recoveries, ranging from 94 to 102%, were obtained by SCX from spiked samples. Although the extraction efficiencies of LLE were lower (87-90%), LLE yielded less complex chromatograms, indicating a purer extract. KEY WORDS: Khat alkaloids, Solid phase extraction, Liquid-liquid extraction, HPLC, Genevac Bull. Chem. Soc. Ethiop. 2015, 29(3), 331-339.DOI: http://dx.doi.org/10.4314/bcse.v29i3.

Synthesis of tetracationic organic salt from 4,4'-bipyridine

This report describes the synthesis of a tetracationic organic salt from 4,4'-bipyridine and 1-bromooctane using 1,3-dibromopropane as a spacer just in three simple steps. A careful monooctylation of one of the nitrogen atoms of 4,4'-bipyridine using 1-bromoocatane followed by the dimeriztion using 1,3-dibromopropane as a linker resulted a tetracationic organic salt of formula [C3H6(C8Bipyr)2]Br4. 1H and 13C NMR, and CHN elemental analysis as well as ultra high vacuum spectroscopic technique (XPS) were employed to confirm the synthesis and the purity of this compound. This compound has demonstrated molar conductivity of 4320 S cm2 mol-1 unexpected from a salt with 1:4 cation to anion ratio. It is expected that this salt would have potential applications in materials such as for low-molecular-weight gelators and the preparation of solid films for organic electronic applications

Phenolic composition and antioxidant activities of cladodes of the two varieties of cactus pear (Opuntia ficus-indica) grown in Ethiopia

In this study, young cladodes corresponding to two (thorn-less and thorn-containing) varieties of cactus pear (Opuntia ficus-indica) from four different areas of Tigray region, Ethiopia, were investigated for their phenolic contents and antioxidant activities. Quantitative estimation of total phenolic contents and antioxidant activities in the cladodes was carried out using spectrophotometric methods. A 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay was used for the determination of the antioxidant activities, while Folin-Ciocalteau reagent, aluminum chloride and protein (albumin) precipitation methods were used for the determination of total polyphenol, flavonoid and tannin contents, respectively. The cladodes were found to be rich in polyphenols, with values in the range 18.0-71.4 mg gallic acid equivalent (GAE)/g of dry weight (DW). The predominant part of the polyphenols is represented by tannins, 9.00-41.2 mg GAE/g of DW, followed by flavonoids, 6.40-25.0 mg catchin equivalent (CE)/g of DW. The cladodes showed strong antioxidant activities, 59.3-85.8% inhibition compared to ascorbic acid. Application of paired t-test on the overall mean total polyphenol contents of samples collected from the different areas revealed the presence of significant variation between the thorn-less (31.6 GAE/g of DW) and thorn-containing (47.7 GAE/g of DW) varieties. One-way ANOVA also revealed that there are significant variations among samples from the same variety but collected from different areas

Levels Of Major, Minor And Toxic Metals In Tubers And Flour Of Dioscorea Abyssinica Grown In Ethiopia

Dioscorea Abyssinica , commonly known as yam, is an indigenous plant in Ethiopia. Its root tuber is used as staple and co-staple food in South Nation Nationality People and Regional State of Ethiopia. This study was carried out to analyze the selected mineral nutrients in the tuber and flour of D. abyssinica grown in different parts of the country for human consumption. Samples collected from five different areas were analyzed for eleven metals (Ca, Mg, Fe, Zn, Cu, Mn, Co, Cr, Ni, Cd and Pb) by flame atomic absorption spectrometry and two metals (K and Na) by flame emission spectrometry. Known weight of oven-dried sample was wet-digested using 3 mL of (69–72%) HNO3 and 1 mL of (70%) HClO4, for 2 h at variable temperature (120–270° C). The validity of the optimized procedure was evaluated by the analysis of spiked samples whose recovery was in the range of 92–105%. The mean concentration range (in μg/g) of each metal in D. abyssinica samples were K (8,469–13,914), Na (133–405), Ca (172–448), Mg (180–354), Fe (28.3–144.5), Mn (12.0–14.5), Zn (12.3–44.5), Cu (7.26–17.6), Co (1.91–8.68), Cr (0.86–3.41) and Ni (2.43–5.31). D. abyssinica could be good sources of essential trace metals to the individuals, more particularly Fe and Zn were higher than the entire trace metals in the samples investigated while Cd and Pb were in minor quantities and hence the plant is free from toxic heavy metals. Consuming 100 g of this tuber per day contribute the following concentration range of Fe, Zn, Cu, Mn, Co, Ni and Cr in mg/100 g per day: 2.8–14.4, 1.2–4.5, 0.73–1.8, ND–1.5, ND–0.87, 0.24–0.53 and 0.09–0.34 mg/100 g, respectively. Statistical analysis revealed that significant variations in metal concentrations among the sampling sites were observed for some of the metals when pair wise test was made while insignificant variation were seen for the remaining metals. D. abyssinica could be a better source of K, Ca, Fe and Zn to human compared to the common cereal flours (barley, wheat and red teff flour) as well as tuber food products like potato, cassava, yam, and enset ( Ensete ventricosum ), while it could be an alternative source of the other essential mineral nutrients to the individual daily mineral intake

Total phenols and antioxidant activities of natural honeys and propolis collected from different geographical regions of Ethiopia

In this study, ten honey and five propolis samples from different geographical origins were tested. Both honey and propolis samples showed high content of total phenolic compounds (330-610 mg gallic acid equivalent (GAE)/100 g honey; 365-1022 mg GAE/g ethanol extract of propolis (EEP). The total flavonoids ranged from (15.1-42.6 mg catechin equivalent (CE)/100 g for honey; to 123-74 mg CE/g for EEP. These honeybee products of Ethiopia had high total radical scavenging properties with respect to 2,2-diphenyl-1-picryl-hydrazyl (DPPH); 18.1-59.8% and 48.6-87.8% for honey and EEP respectively. Furthermore, the hydroxymethylfurfural (HMF) of the honey samples was found to be low with a mean value of 4.8 mg/kg suggesting that the samples were of good quality. The antioxidant properties of the products showed a good correlation (r2 = 0.50-0.82) with their polyphenolic contents

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

Ethnopharmacological relevance: Khat, 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. Materials and methods: Cathinone 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. Results: The 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 1.0×10−6 cm/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. Conclusions: These 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 swallowe

Evaluation of the effect of various drying techniques on the composition of the psychoactive phenylpropylamino alkaloids of khat (<i>Catha edulis</i> Forsk) chewing leaves

The study demonstrated that by freezing or drying under different conditions, cathinone could be detected in the khat (<i>Catha edulis</i> Forsk) samples that have been harvested for more than four months. Freeze drying or freezing in the refrigerator (-20 ^oC) yielded more than 73% of cathinone. Air drying, sun drying or oven drying at 60 ^oC resulted in a cathinone composition of 57%, 42% and 36%, respectively. The study confirmed that, freshly harvested tender leaves of khat contained exclusively of cathinone but upon sun drying, part of it decomposes to cathine and norephedrine leaving cathinone as a major component. Thus it is wrong to assume that sun drying the leaves can result complete conversion of cathinone to cathine and norephedrine. Furthermore, the results of the study confirmed that it was possible to preserve khat samples for longer periods after freeze drying or deep freezing without significant loss of cathinone.DOI: http://dx.doi.org/10.4314/bcse.v27i3.