Background: Coffee is a well-known beverage that is widely used around the world. Despite the wide use of coffee in Ethiopia, there is a lack of extensive studies addressing the issues related to the caffeine content and hydrogen peroxide antioxidant activity of varieties of coffee types, particularly in Habru woreda, Ethiopia. Objective: This study aimed to determine the caffeine content and hydrogen peroxide antioxidant activity of raw and roasted coffee beans collected directly from Habru woreda, North Wollo zone of Ethiopia. Methods: The study was conducted in Bohoro, Girana, and Wurgisa kebeles of Habru woreda, Ethiopia, by collecting 500 g of green beans of Arabica coffee without considering their variety. Then, the collected beans were divided into raw and roasted coffee to perform aqueous and dichloromethane extraction of their caffeine content and hydrogen peroxide antioxidant activity using UV-Vis spectrophotometry. Results: The amounts of caffeine in aqueous and dichloromethane extraction were in the range of 124.01−191.27 ppm and 145.15−200.09 ppm in raw and roasted coffees, respectively. Using the IC 50 value, the hydrogen peroxide scavenging activity of the aqueous phase coffee bean extracts in Bohoro raw, Bohoro roasted, Wurgisa raw, Wurgisa roasted, Girana raw, and Girana roasted coffee were 32.17 ppm, 11.69 ppm, 26.14 ppm, 3.12 ppm, 24.83 ppm, and 11.06 ppm, respectively, while that of ascorbic acid was 6.91 ppm. Conclusion:The study showed that the highest amount of caffeine in both aqueous and dichloromethane solvent extraction was found in Bohoro's raw and roasted coffee beans. Also, the amounts of caffeine in all coffee bean samples were safe and the antioxidant activity was excellent. In most of the samples, significant variations in the concentration of caffeine in raw and roasted coffee bean samples were observed in the two extraction solvents.
One of the inputs for a high-quality education is using laboratory activities which are characteristic features of science teaching at all levels of education. Consequently, this study was carried out to investigate the perception and practice centered on assessing the practice of laboratory work and identifying the factors that affect its implementation. To achieve these objectives, data were collected from secondary school students and teachers. In doing this study, quantitative and qualitative research methods and a descriptive survey design were used. Stratified random sampling was used in the selection of study participants. The data were obtained through questionnaires, observation, and interviews. Based on the analyzed data, the findings of the study revealed that both students and teachers perceived that chemistry practical courses (experiments) are relevant to students learning. The findings of the study also showed that despite its relevance, the practice of laboratory work is very low. Furthermore, the lack of resources (such as laboratory equipment), the lack of time to practice laboratory work, and students’ lack of engagement in laboratory activities were the major factors that affect the implementation of laboratory work. Finally, recommendations were made based on the major findings to improve the practice of laboratory work.
Sequential extraction of the roots of Kniphofia insignis using cold maceration techniques and column chromatographic separation leads to the isolation of one monomeric anthraquinone, chrysophanol (1). The structure of the compound was established using spectroscopic analyses including NMR (1H and 13C-NMR, infrared) and comparison with reported literature. The in vitro antibacterial activities of the crude extracts and the isolated compounds were evaluated against four bacterial strains (S. aureus ATCC 25923, B. subtilis ATCC 6633, E. coli ATCC 35218, and P. aeruginosa ATCC 27853). Among them, the crude extract, acetone extract, has shown substantial antibacterial activity with the highest activity against E. coli (22.3 mm). However, compound 1 has a better zone of inhibition with 19.3 mm against P. aeruginosa.
A new hybrid nanomaterial has been developed by inducing catalytic silver nanoparticle on supramolecular BN nanosheets using supramolecular polymer as hybrid coordinator for photocatalytic removal of reactive blue dye (RB 221) from aqueous solution. In this study, adenine-bifunctionalized polypropylene glycol diacrylate (APPG) polymer was used for exfoliation and modification of BNNSs to decorate Ag nanoparticles that are prepared by sonication-assisted liquid phase exfoliation techniques. The synthesized materials are systematically characterized by various techniques such as FT-IR, UV-visible spectroscopy, Raman, FE-SEM, and HR-TEM. The layered structure of supramolecular polymer was observed over the exfoliated few layered BNNSs (2.0 to 3.5 nm). HR-TEM show that the silver nanoparticles (Ag NPs) were successfully decorated on supramolecular functionalized BN nanosheets. The significance of functionalization is that the adenine moieties induce the high amount of Ag NPs through Ag/adenine moiety coordination, thereby increasing the effectiveness of catalyst towards removal of RB 221 dye. The RB 221 dye removal efficiency of new synthesized nanomaterials such as BN/APPG/Ag (1 : 2.5), BN/APPG/Ag (1 : 1), APPG/Ag, and BN/Ag were 84.60 ± 1.26 % , 70.13 ± 0.034 , 65.60 ± 0.052 , and 35.0 ± 0.45 % , respectively. The photocatalytic dye degradation performance of catalyst increases with high amount of supramolecular polymer in the composites. Reusability of analysis revealed that regenerated BN/APPG/Ag catalyst could be tested in at least three consecutive cycles in which proving efficiency removal of the RB 221 was found to be 83.7 ± 0.8 , 63.8 ± 0.51 , and 54.60 ± 0.78 % after the first, second, and third cycles of reuse, respectively. In addition, the absorption peaks of the RB 221 in solutions undergo upshifts relative to the free dye indicating the reduction of RB 221 dye for only BNNSs containing composite catalysts. Overall, the findings of this work are promising and therefore propose that BN/APPG/Ag could be applicable for the removal of dyes repeatedly for wastewater treatment in environment as result of their reusability and versatility.
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