Fatty Acid Profile, Total Phenolic Content, and Antioxidant Activity of Niger Seed (Guizotia abyssinica) and Linseed (Linum usitatissimum)

Fatty acid composition and antioxidant content are major determinants of vegetable oil quality. Antioxidants are important food components, and there is an increasing interest of replacing synthetic antioxidants with those from natural sources for food industry. The objective of this study was to evaluate fatty acid composition, total phenolic, carotenoid and chlorophyll contents, and antioxidant capacity of different varieties of two oilseed crops. Five niger seed and eight linseed varieties were used. For the analysis of fatty acid composition of the seed oil, gas chromatography method was used. Standard methods were used for total phenolic, carotenoid and chlorophyll contents, and antioxidant properties. In niger seed oil, linoleic acid (C18:2) was the dominant fatty acid, accounting for 73.3% (variety Esete) to 76.8% (variety Ginchi) of the total fatty acids. In linseed oil, linolenic acid (C18:3) was the dominant fatty acid accounting for 55.7 (variety Chilalo) to 60.1 (variety Belaye-96). The total phenolic content ranged from 22.4 mg GAE/g (variety Esete) to 27.9 mg GAE/g (variety Ginchi) in niger seed and from 20.5 mg GAE/g (variety Belay-96) to 25.4 mg GAE/g (variety Ci-1525) in linseed. In niger seed, variety Fogera had the highest values for FRAP and radical scavenging activity. The carotenoid content also showed significant variation among the varieties ranging from 2.57 (Esete) to 8.08 (Kuyu) mu mol/g for niger and 4.13 (Tole) to 8.66 (Belay-96) mu mol/g for linseed. The FRAP assay showed that variety Fogera of niger seed and variety Chilalo of linseed came on top among their respective varieties with values of 57.2 and 30.6, respectively. Both niger seed and linseed were shown to be rich in bioactive compounds. However, significant variation was observed among the varieties of each crop and among the two crops in their total phenolic and carotenoid contents as well as ferric reducing potential and radical scavenging capacity. Principal component analysis revealed the presence of more than one group in both niger seed and linseed. Hence, genetic variation among the varieties should be utilized for improving their desirable characteristics through breeding. Both oil crops can be used as the source of antioxidants for replacing synthetic compounds

Mineral and Anti-Nutritional Contents of Niger Seed (Guizotia abyssinica (L.f.) Cass., Linseed (Linumusitatissimum L.) and Sesame (Sesamumindicum L.) Varieties Grown in Ethiopia

Oilseeds are rich sources of micronutrients and contribute to combating malnutrition caused by micronutrient deficiency. The objective of this study was to investigate the mineral and anti-nutritional contents of different varieties of niger seed, linseed and sesame. Five niger seed, eight linseed and ten sesame varieties were used. Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) was used for mineral analysis and the standard method was adopted to estimate tannin and phytate. Twelve mineral elements; Ca, K, Mg, Na, P, B, Cu, Fe, Mn, S, Se and Zn were analyzed for each oilseed variety. In niger seed, phosphorous was the most abundant mineral element ranging from 661 to 867 mg/100 g and selenium was the least, ranging from 0.1 to 0.33 mg/100 g. Potassium was recorded in the range of 502 to 732 mg/100 g for linseed varieties. Calcium was the most common mineral element in sesame (1112 to 1787 mg/100 g). The average phytate contents of niger seed, linseed and sesame varieties were353 mg/100 g, 104 mg/100 g and 285 mg/100 g, respectively. Tannin ranged from 91 to 201 mg/100 g, 96 to 695 mg/100 g and 85 to 660 mg/100 g in niger seed, linseed and sesame, respectively. In conclusion, there is a significant variation among the varieties within each crop species as well as among the different oilseeds in terms of their mineral and anti-nutritional contents

Excessive pruning and limited regeneration: Are Faidherbia albida parklands heading for extinction in the Central Rift Valley of Ethiopia?

Scattered Faidherbia albida trees provide multiple ecological and production benefits across the Sahel. The intensive management and use of this important tree may impede its regeneration. Regeneration bottlenecks were explored and population dynamics modelled. On experimental plots in which seed of F. albida was sown, exposure to the first 2 months of dry season resulted in a quarter of seedling mortality. Exposure to season‐long free grazing and browsing caused significantly greater seedling mortality. Results from monitoring 100 permanent plots scattered over the landscape showed that adult population density was 4.2 ± 0.3 (mean ± SE) trees ha−1 and dominated by old age classes. Sixty percent of the total population were older than 30 years. The mean density for juveniles was 1.4 ± 0.2 (mean ± SE) individuals ha−1. The annual rates of decline were 1.2%, 51.3%, and 63.2% for adults, seedlings, and saplings, respectively. Our model predicted that the F. albida population will start to decline within 1–2 decades to eventually fall below 1 tree ha−1 within 60 years under current management. The model highlighted that the limited seed source, caused by excessive pruning, was the main constraint for recruitment. Appropriate land management policy to ensure adequate seed production would avert current trends in decline of F. albida population