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Masters Degrees (Horticultural Science)

Permanent URI for this collectionhttps://hdl.handle.net/10413/6628

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Browsing Masters Degrees (Horticultural Science) by Subject "Antioxidants."

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    Antioxidants composition of moringa (moringa oleifera lam) in different plant organs.
    (2015) Mohammed, Fatima Abdelkarim Abdelrahman.; Tesfay, Samson Zeray.
    Moringa oleifera Lam. is a versatile plant with various benefits; different parts of the plant have different pharmacological activity such as flavonoid, alkaloids, phenol, and carotenoids. The aim of the seed study was to investigate phytochemicals composition change and their utilization during seed and seedling germination. Seeds were germinated using three different temperature regimes (30/20 °C, 25/15 °C and 20/10 °C). Spectrophotometric determination of proline and phenols was carried out, while sugars were analyzed using HPLC-RID. The data were collected and analyzed using statistical software GenStat 14.1. Results of seed showed significant differences on speed of seed germination at temperature of 30/20°C followed by 25/15°C and 20/10°C respectively. Seed carbohydrates composition changes were observed with germination hours sucrose concentrations peaked within 24h (16 mg/g DW) and the same sugar showed sharp decrease for 96h (6.4 mg/g DW). Glucose and fructose concentrations also increased for 96h (2-6 mg/g DW). Also temperature had significantly influenced the biosynthesis and accumulation of biochemical compounds in the seeds especially 30/20°C. Temperature 30/20°C, increased seed phenols and proline concentration. Phenols and proline started to accumulate at 72h, after seed germination presumed within 48h. Results of leaves showed that Temperature also had significant effect on phenols the proline concentration particularly, 35/18°C, followed by 30/15°C, 25/12°C. The antioxidant levels of post germination phase was investigated, the result showed significant differences in antioxidant concentrations and sugar distribution in various parts of Moringa seedling. The leaf was recorded the highest antioxidant concentration (1.7 mg g-1). Moringa leaf also recorded the highest total phenols. The highest sugar concentration was found in root (258.9 mg g-1), and stem (245.72mg g-1) followed by root and seed. The highest concentration of total crude protein (110.4mg g-1) and vitamin E (28.57 μg g-1) was found in seed. The carotenoids concentration was the highest in the root (29 mg g-1). The result also showed different nutrients at various concentrations on different parts of Moringa tree. High phosphorous accumulated in leaf and seed; Potassium accumulation was found in root, stem, and seed coat. It is concluded that temperature treatments of Moringa seed and leaves resulted in significant differences in the rate of germination and biochemical compounds. Furthermore, the present study showed that Temperature plays an important role in germination seed and development of M. oleifera and antioxidants, phenolic, proline and carbohydrates contents. Further research on the effect of temperature on germination of M. oleifera and biochemical compound is therefore recommended.
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    A comparative study of antioxidant potentials of some leafy vegetables : emphasis on African leafy vegetable and exotic vegetables.
    (2014) Mathe, Sakhile.; Tesfay, Samson Zeray.
    Due to malnutrition and food insecurity problem around the globe, mainly in developing countries, cheap nutritional food sources are required. In South Africa, a large proportion of the population is considered “poor” and with limited resources. However, South Africa as a whole is rich in indigenous leafy vegetables which have the capacity to help mitigate the problem of malnutrition and food insecurity. Amaranthus hybridus, an African indigenous leafy vegetable was tested for seed quality and potential essential antioxidants. Exotic (to Africa) leafy vegetables (Brassica oleracea and Brassica oleracea var. capitata f. rubra) were used as references for potential antioxidants. Amaranthus hybridus seed quality was tested using two different coloured seeds, red and white gold. Seed viability and vigor were tested using germination, electrolyte leakage and antioxidant content. Data recorded indicated better seed quality for red seeds than white gold seeds; therefore red coloured seeds were planted along with purchased Brassica oleracea and Brassica oleracea var. capitata f. rubra for quantifying antioxidant content. Selected antioxidant types were measured on weekly harvests of the studied vegetables. From the results it was evident that the indigenous leafy vegetable amaranth with total antioxidants [FRAP(3174.91 mmol Fe2 SO4 100g-1 DW) and DPPH(8.3 mmol trollox 100g-1)], proteins (6.88 mg.g-1 DW), total phenols ( 345 mg 100g-1 DW), flavonoids (79 mg 100g-1 DW), Chlorophyll and carotenoids (2.8 mg 100g-1 DW), ascorbic acid (86 mg 100g-1 DW) and soluble sugars (1.07 Brix %), could be used in conjunction with available commercial leafy vegetables to combat malnutrition and food security problems. Further, these results indicate that in resource limited regions this vegetable can act as a main source of nutrients and a supplement in resource abundant regions of the country and/or continent. Further, analysis of selected enzymatic antioxidants was carried-out on leaf material of the studied vegetable to evaluate the capability of indigenous leafy vegetables to protect themselves against oxidative damage. Indigenous leafy vegetables exhibited high antioxidant activity against lipid peroxidation at early stages of growth and high antioxidant enzyme activity at similar stages thus high capability of mitigating ROS effect. Data obtained from the study indicated that indigenous vegetables are a good source of essential antioxidants which are beneficial to human health; therefore the intensity of their use needs to be increased, especially in areas of high prevalence of malnutrition and diseases.