Alemayehu Paulos Washe

ABSRACT The current boom in the industrial sector of the country is arise scientific concern about environmental contamination by heavy metals such as chromium. The objective of this project is to fabricate a sensitive and selective electrode for differential pulse voltammetric determination of Cr (VI) in water samples and demonstrate its applicability in complex matrices such as tannery effluent. The drop casting method is use for electrode development. Experimental variables that can influence the DPV response of the developed electrode for Cr (VI) including strength of supporting electrolytes, pH of the solution, and concentration parameters were optimized. The figures of merit of the developed electrode were evaluated and the applicability was demonstrated through determination of Cr (VI) in tannery effluent water. The developed electrode was detected a very low level of Cr (VI) in acetate buffer at pH 5 with limit of detection and limit of quantification 0.0885 and 0.2950 μmol L⁻¹, respectively. The linear calibration plot is R² value of 0.999 suggesting a very good correlation between DPV current response and concentration of Cr (VI). The current electrode was simple to develop and can successfully be applied for the determination of Cr (VI) in wastewater samples.

Certain natural dietary spices, in addition to their use in food flavoring and preservation, have the ability to detoxify or degrade a wide range of chemical carcinogens. In the present study, aqueous extracts of judiciously selected natural dietary spices were evaluated for their ability to degrade aflatoxin B1 (AFB1). A total of 9 spices including garlic (Allium sativum), ginger (Zingiber officinale), black cumin (Nigella sativum), clove (Syzygium aromaticum), sacred basil (Ocimum basilicum), lemon grass (Cymbopogon citratusL. (DC)Stapf)), thyme (Thymus schimperi), fenugreek (Trigonella foenum-graecum), and lemon traditionally used by the Ethiopian Community for food flavoring and preservation were considered. Aflatoxin degradation efficacy of the spice extracts was studied through determination of the toxin in extract-treated and nontreated samples using LC-MS/MS. The degradation was characterized by electrochemical methods based on the characteristic oxidation peak of phenolic hydroxyl resulting from the degradation of the toxin after treatment with the extracts. Of the various spices, garlic showed the highest 35.8% (30 min) to 61.7% (1 hr) in spiked and 46.7% (30 min) to 68.3% (1 hr) and real-sample (contaminated maize) treatment reduction followed by lemon 34.2% (30 min) to 56.0% (1 hr) in spiked and 41.1% (30 min) to 60.6% (1 hr) in real-sample treatment at 25°C. The level of reduction was higher in real-sample treatment than that in spiked. This suggests adsorptive contribution by the matrix in addition to the chemical degradation. The current findings revealed nonobvious benefits of the use of natural dietary spices as effective solution for AFB1 degradation and decontamination of food.

Screen printed carbon electrodes (SPCEs) provide attractive opportunity for sensitive and selective determination target analytes in clinical samples. The aim of the current work was to develop SPCEs based sensor for the determination of uric acid in clinical serum samples. The electrodes were pretreated by soaking in N,N-dimethylformamide for 5 minutes followed by drying in an oven at 100°C for 20 mins. The effect of surface pretreatment was characterized using cyclic voltammetry. The current response of uric acid detection was improved by a factor of 3.5 in differential pulse voltammetric measurement compared to unmodified electrode. Under the optimized conditions, the sensor displayed two dynamic linear ranges 5-100 μM and 100-500 μM with correlation coefficient, R², values of 0.98782 and 0.97876, respectively. The limit of detection and limit of quantification calculated using the dynamic linear range 5-100 μM were 1.9 x 10⁻⁷ M and 6.33 x 10⁻⁷ M, respectively. The developed sensor displayed well separated and discerned peaks for UA in presence of the potential interferent (ascorbic acid and citric acid). The electrode was successfully applied for the detection of very low level of UA in clinical serum samples in a phosphate buffer solution (pH = 7). The proposed sensor showed a very high reproducibility and repeatability with the relative standard deviation of 0.9%. In conclusion, a simple and low cost sensor based on SPCEs is developed for sensitive and selective detection of uric acid in clinical samples.

Aflatoxins contamination of maize exhibits a serious threat to human and animal health over the past few decades. To protect the safety of food commodities, regular monitoring for afltoxins in food is necessary. In the proposed study, we have followed a rapid and sensitive biosensor approach as well as thin layer chromatography method for quantification of aflatoxins. Our data demonstrate that all the samples tested were beyond the safety level of aflatoxins as determined by Food and Drug Administration and European Union. Results of fungal mycoflora evidenced the massive presence of Aspergillus species (75 %) followed by Fusarium (11 %), Penicillium (8 %) and Trichoderma (6 %) as characterized by biochemical and sporulation properties. Use of internationally developed biosensor for detection of fungal toxin in this work is the first approach that was utilized in the developing country like Ethiopia. In the end, we conclude that fungal contaminant and there metabolites are potential threat to the agricultural industry and require urgent intervention.

Aims: To evaluate the hepatoprotective activity of Stephania abyssinica (S. abyssinica) and isolate the bioactive constituents. Study Design: The in vivo hepatoprotective activity of the extracts was evaluated by measuring serum levels of biochemical parameters of liver function in carbon tetrachloride (CCl₄) treated rats. Place and Duration of Study: A preliminary survey was conducted in the rural areas of Wolaita (Southern part of Ethiopia) from September to December 2015. Pharmacological and phytochemical studies were conducted at the Laboratories of Department of Pharmacology, and Department of Chemistry of Dilla University. Methodology: The in vivo hepatoprotective activity of methanolic extracts of roots and rhizomes of the plant was studied by determining serum levels of the biochemical markers of liver function including glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), alkaline phosphatase (ALP), total protein, and bilirubin concentrations before and after treatments with CCl₄ and plant extracts. Bioactive principles were isolated by fractionation followed by concentration by preparative Thin Layer Chromatography. The structures of the compounds were elucidated using spectroscopic techniques including ¹H NMR, ¹³CNMR, DEPT-135, ¹H-¹H COSY, HMQC and HMBC. Results: Administration of CCl4 alone to the rats significantly increased the total bilirubin concentration, GOT, GPT, and ALP (P = 0.05). However, simultaneous injection of oral dose of 200 mg/kg b.wt of the extracts reduced the serum levels of the enzymes by 53.42, 33.62, and 55.00% respectively. When 100 mg/Kg b.wt standard drug Silymarin was used, the decrease in the enzyme levels was by 44.00, 66.84, and 58.36%. Our fractionation experiments led to the identification of new hasubanan type alkaloid named as 6-(3’-hydroxy-4’-methoxycinnamoyl) stephine and the containing fraction displayed moderate hepatoprotective activity. Conclusions: The observed hepatoprotective activities of methanolic extracts of roots and rhizomes of S. abyssinica lend credence to its claimed traditional use against liver diseases.

Ozone (O₃) phytotoxicity is a serious concern all over the globe. O₃ can cause both biochemical and physiological changes to plants that could lead to reduction in growth and yield. Its effect on agricultural crops is usually detected as foliar injury. Although foliar injury has frequently served as physiological basis for monitoring performance of agricultural crops and assessing air quality, its visibility depends on period of exposure, concentration of ozone, and environmental conditions. The present study focused on the determination of biochemical indicators of ozone phytotoxicity including Rubisco (biochemical indicator for carbon assimilation), photo-pigments [carotenoids and chlorophyll (a & b)], and chlorophyll photochemical efficiency on a judiciously selected plant-Nicotiana tabacum (Tobacco), variety: Little Havanna. An enclosed computer controlled growth chamber was used for cultivation of the experimental plant groups (ozone exposed and control). Spectrophotometric measurements of the biochemical indicators were carried out to evaluate the exposure-response behaviour of the plant. Our results showed a significant (P< 0.05) decrease of the biochemical indicators that is reproducible even when foliar injury is not detected. Besides, experiments also showed that chlorophyll a is more sensitive to ozone than chlorophyll b. The instrumental readings were supported by a reduction in total organic nitrogen and starch content and ultimate decrease in growth rate and root: shoot ratio. While significant variations in the intensities of foliar injury can be detected among plants within a group, a reproducible exposure-response data were obtained from instrumental measurements. Such measurements can also serve as basis for the development of implantable sensors for in-situ monitoring of ozone pollution in sensitive crops.