Abstract
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.Key words: Moringa stenopetala, Antioxidant potential, Ferric reducing antioxidant power (FRAP), 2,2-diphenyl- 1-picrylhydrazyl (DPPH) radical, Folin-Ciocalteu’s phenol reagent (FCR), Peroxide value (PV).
Highlights
The rapid rise of degenerative diseases is threatening economic and social development as well as claiming the lives of millions of people worldwide
The present study showed that scavenging of DPPH radicals by aqueous methanol extracts of powdered Moringa leaves occurred in a dose-dependent manner, an observation that has been reported for leaf extracts of M. oleifera (Kumar et al, 2012) and M. peregrine (Dehshahri et al, 2012)
Lower values of Peroxide value (PV) and Conjugated dienes (CD) contents for sunflower oil containing M. stenopetala leaf extract relative to the control indicated effectiveness of the extract in preventing oxidation of the oil. It has been noted in the present study that the ability of Moringa leaf extracts to deter oxidative deterioration of sunflower oil is comparable to that of the familiar antioxidant vitamin E
Summary
The rapid rise of degenerative diseases is threatening economic and social development as well as claiming the lives of millions of people worldwide. It is estimated that up to 80% of cardiovascular diseases, 90% of Type II diabetes, and one third of cancers can be avoided by changing life-style, including diet (Stampfer et al, 2000; Hu, 2001; Key, 2002). Diet-related high cholesterol, high blood pressure, obesity, and insufficient consumption of fruits and vegetables have been cited as significant interlinking risk factors that cause the majority of these diseases (WHO, 2003). It is widely believed that the main causes of these diseases are highly reactive chemical species known as free radicals. Notable among the free radicals are the reactive oxygen species (ROS) such as superoxide anion radical (O2 ̄ ), hydroxyl radical (HO) as well as the non-radical molecule hydrogen peroxide (H2O2), all of which occur in the body either as a result of normal metabolic processes or enter the body from external sources. Cell damage caused by free radical-induced chain reactions ap-
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