The present work explores the production of biogas from fruit and vegetable wastes mixed with cow manure in an anaerobic digester. The total solid, volatile solids, moisture content and ash content of the wastes were examined. The materials used as feed were avocado, papaya, mango, tomato, banana peel, and cow manure. Varying volumes of digesters were employed for biogas generation. The combustibility of the gas so generated was tested. The anaerobic digestion of fruit and vegetable wastes mixed with different waste took 55 days to produce biogas (for complete digestion). Anaerobic digestion is very sensitive to change in pH and it is important to maintain pH of 6.7-7.4 for healthy system. The temperature of the digester and the environment also affects the anaerobic digestion process. Upon adjustment of the factors affecting anaerobic digestion, it is felt that co-digestion between FVW and CM produces biogas without need of nutrient or chemical addition to the system. The search for alternative source of energy such as biogas should be intensified so that ecological disasters like environmental pollution, deforestation, desertification and erosion can be arrested.
This study was conducted to assess the antioxidant potential of Moringa stenopetala leaf obtained from a private garden in Bahir Dar City and powdered Moringa leaf purchased from a supermarket in Bahir Dar City by using ferric reducing antioxidant power, 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity, peroxide value and conjugated diene hydroperoxide assays. The powdered Moringa stenopetala leaf extract was invariably found to have a higher antioxidant capacity than the purchased Moringa powder. In the conjugated diene hydroperoxide and peroxide value assays, sunflower oil was used as an oxidation substrate. Both peroxide value and conjugated diene concentration for sunflower oil containing extracts of Moringa leaf and purchased Moringa powder were found to be lower than the corresponding values observed for the control showing the effectiveness of the extracts in delaying oxidation of the oil. The total phenolic content, in terms of mg gallic acid equivalent per 100 g of dry weight of sample was found to be 92.8 ±1.01 and 75.5 ± 2.28 for, respectively, powdered leaves of M. stenopetala and purchased powder of Moringa leaf. The antioxidant capacity of the powdered Moringa stenopetala leaf and purchased Moringa powder were found to be, respectively, 442.0±10.58 and 291.3±15.52 mg of ascorbic acid equivalent per 100 g of dry weight of plant sample in the FRAP assay. The corresponding values for the powdered Moringa stenopetala leaf and purchased Moringa powder in the DPPH assay were found to be, respectively, 144.0±0.53, 138.8±1.05 mg of ascorbic acid equivalent per 100 g of dry weight of the sample. This difference in antioxidant capacity of these two samples can be attributed to differences in their total phenolic content. It is suggested that this antioxidant potential of the leaves of Moringa stenopetala may underlie the widespread use of the plant in traditional medicine.
The methanolic extract of the fresh leaves of khat/Catha edulis was investigated using established procedures for its phytochemical constituents and effect on lipid oxidation. The phytochemical analysis revealed the presence of alkaloids, tannins, phenols, and flavonoids. The effects of the extract on oxidation of locally produced edible NSO (niger seed oil) was assessed through the measurement of peroxide value, iodine value and conjugated diene concentration for a period of sixteen days. Control setup involving NSO without the extract was also kept for the same period of time under similar conditions. It was observed that the peroxide value and conjugated diene value of the oil containing varying concentrations of the extracts of khat leaves increased significantly, relative to the control, showing that the extract of the khat leaves promoted deterioration of the oil. In a similar manner, the iodine value of NSO with and without added khat leaves extract was assessed. It was observed that the iodine value of the oil containing the khat leaves extract decreased more rapidly than the control, suggesting that the double bonds in the fat constituting the oil were diminished by the extract of the khat leaves. It is thus inferred from the present study that methanolic extract of fresh khat leaves leads to deterioration of NSO. It can also be suggested from the results of the present investigation that the health problems khat chewers face may be related to the oxidative damaging effects of these leaves exert on biomolecules found in the body.
The study was aimed at investigating the phytochemicals, antioxidant and antibacterial activities of the ethanolic and methanolic extracts of Aloe elegans leaves gel. The phytochemical screening revealed the presence of phenols, flavonoids, anthraquinones, tannins, sapponins and terpenoids in both extracts. The antioxidant activities of both extracts were assayed using ferric reducing antioxidant power (FRAP), conjugated diene (CD) and peroxide value (PV) methods using sunflower oil (SFO) as the oxidizable substrate. The value for methanol and ethanol extracts of Aloe elegans leaves gel and the standard ascorbic acid in the ferric reducing power assay at 20 µg/mL were found to be 65.32%, 62.89%, 59.4% respectively. The peroxide value after 12 days at room temperature for the Sunflower oil (SFO) was found to be 45 mmol/L while the value for the substrate containing methanol, ethanol extract and vitamin E were found to be 36, 38, 43 mmol/L respectively. The value of the absorption coefficients of conjugated dienes resulted from oxidations of the methanol and ethanol extracts and vitamin E were found to be 3.006, 3.387, 4.306 g-1 cm-1 mL respectively. In all the antioxidant assays used, the methanolic extract was found to inhibit oxidation of sunflower oil to a better extent than its ethanolic counterpart. Relative to vitamin E, both extracts exhibited better antioxidant efficacy. In the antibacterial assay, both the extracts showed potent bactericidal effects against Escherichia coli and Staphyloccus aureus, though to a lesser extent than the standard antibiotic Gentamicin.
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