Nanoparticle fabrication using plant extracts is an important alternative method because it is non-toxic, biocompatible, and environmentally friendly. In this study, green synthesis of MgO nanoparticles using Moringa oleifera leaf water extracts was conducted by mixing the extract and a solution of magnesium chloride. The product was characterized using different techniques, i.e. UV-Visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The UV-Vis spectrum of MgO nanoparticles shows an absorption at 280 nm. The size of the synthesized MgO nanoparticles ranges from 20-50 nm. The antibacterial activity of MgO nanoparticles was seen from the zone of inhibition against Staphylococcus aureus (6.3 mm) and against Escherichia coli (6 mm). MgO nanoparticles have been successfully fabricated using Moringa oleifera leaf aqueous extracts, providing an alternative method for synthesizing MgO nanoparticles. KEY WORDS: Antibacterial activity, Escherchia coli, MgO nanoparticles, Moringa oleifera, Staphylococcus aureus Bull. Chem. Soc. Ethiop. 2021, 35(1), 161-170. DOI: https://dx.doi.org/10.4314/bcse.v35i1.14

In this research, magnesium oxide nanoparticles (MgONPs) was prepared from MgCl2 solution using aqueous extract of Moringa oleifera (M. oleifera) bark as green agent. Preparation procedure involved mixing of MgCl2.6H2O solution and the aqueous extract of M. oleifera bark, followed by drop wise addition of NaOH solution. The formation of MgONPs in this study was confirmed using UV-Vis absorption. The spherical crystal structure of MgONPs was confirmed by XRD analysis. The average particle size of the synthesized MgONPs was found between 60—100 nm using SEM and TEM images and PSA results. The MgONPs synthesized showed good antioxidant activity, as well as antibacterial activity against S. aureus, E. faecalis, E. coli, and S. dysenteriae bacteria.

In this research, nano-size MgO (NS-MgO) was prepared from MgCl ₂ solution using aqueous extract of Moringa oleifera leaves (AEMOL) as green agent. Preparation procedure involved mixing of MgCl ₂ .6H ₂ O solution and the AEMOL, followed by dropwise addition of NaOH solution. The formation of NS-MgO in this synthesis was confirmed using UV-Vis absorption. The spherical crystal structure of NS-MgO was confirmed by XRD analysis. The average particle size of the synthesised NS-MgO was found between 40–70 nm using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images and particle size analyser (PSA) results. Based on the maximum inhibition concentration (MIC) it was found that the NS-MgO has good antibacterial activity against S. aureus , E. faecalis , E. coli , and S. dysenteriae bacteria (MIC values: 250–500 μ g ml ⁻¹ ), and much stronger antifungal activity against A. flavus , A. niger , and C. albican (MIC values: 62.5–125 μ g ml ⁻¹ ). These findings suggest prospective potential of NS-MgO synthesised as therapeutic candidate for the treatment of candidiasis.

In this work, we reported a comparative study on the phytochemical screening and antioxidant activity of aqueous extract from different parts of Moringa oleifera plant, i.e. leaves, twigs, stem barks, and woods. The phytochemical content of each extract was screened through qualitative analysis and followed by quantitative analysis for the determination of total phenolic content and total flavonoid content. The results showed that different parts of Moringa oleifera plant would give different extracted natural products. Either leaf or twig part of Moringa oleifera contained alkaloids, flavonoids, saponins, carbohydrates, polyphenols, proteins, amino acids, and phenolics. Meanwhile, only flavonoids, carbohydrates, and phenolics were found in the aqueous extract of the wood part of Moringa oleifera. In agreement to the phytochemical assay, the aqueous extract of leaf part of Moringa oleifera gave the highest total phenolic content (684 ± 16.7 µg GAE mL-1) and the highest flavonoid content (514 ± 26.1 µg CE mL-1) than other parts. Consequently, the leaf extract exhibited the highest antioxidant activity (64.6 ± 0.69%) which is close to the antioxidant activity of ascorbic acid (71.7 ± 0.56%) as the positive control. This finding is critical for the utilization of Moringa oleifera leaf part as the most potent source of antioxidant agents in the future.

Natural and synthetic zeolites are well-known materials sharing a wide range of applications, such as adsorbents, ion exchange, and catalysts. However, synthetic zeolites are more widely used, due to several limitations of natural zeolites, such as the presence of impurities and diverse compositions. In this study, rice husk silica (97.86% purity) and aluminum hydroxide were utilized for the preparation of ZSM-5, to study the effect of crystallization time on the physical characteristics and catalytic activity in the transesterification of Ricinus communis oil. The raw materials, with molar ratio of SiO₂:0.025Al₂O₃:0.165Na₂O:25H₂O, were subjected to crystallization at 180 °C for 48, 72, 96, and 120 h, completed by 6 h calcination at 600 °C. The formation of ZSM-5 was demonstrated by FTIR, XRD, and SEM techniques, confirmed that the formation of ZSM-5 had taken place at 48 h crystallization, with no significant change with prolonged time. The PSA indicates the existence of two clusters of particles, and the BET confirmed the existence of the zeolites as porous materials, with the sample prepared with crystallization time of 96 h had the largest surface area and smallest pore diameter. This particular sample exhibited the highest activity, resulting in 96% conversion of Ricinus communis oil.