Nutritional and Phytochemical Analysis of Different Dried and Fresh African Indigenous Leafy Vegetables Grown in Nairobi, Kenya
Nyambura, Were Yvonne
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Vegetables are an important contributor to human wellbeing through support of the normal functioning of the diverse body systems. They supply the cells with minerals, essential oil, fiber, and phytonutrients. African Leafy vegetables are economical in monetary terms as well as highly nutritious hence people have adapted to their consumption in fresh and dried forms. However, the nutritive difference between dried and fresh vegetables has been scarcely reported. It is then, important to document the nutritional and phytochemicals composition of dried and fresh African Indigenous leafy vegetables. The study was carried out in Kimathi estate in Kamukunji Sub–County in Nairobi County to determine nutritional and phytochemical content fresh and dried Amaranthus hybridus, Solanum nigrum and Vigna unguiculata. The plants were grown in an experimental farm and their leaves were harvested 40 days after planting. The analysis was carried out using standard methods in which carbohydrate was determined using subtraction method; protein was determined using kjedhal method; ash was determined using dry ashing method; fibre was determined using gravimetrical method; fat was determined using soxhlet extraction method; moisture was determined using thermal drying method, vitamins and minerals content was determined using spectrophotometry method ; Alkaloids, Saponins and Phenols was carried out using precipitation method; Flavonoids and Tannins was determined spectrophotometrically; and Hydrogen Cyanide was determined using titration method. The results were given in dry weight basis (DWB). The vegetables’ samples contained between 25.33 and 44.33 μg.100g Zn, 101.0 – 220.00 μg.100g Fe, 2.44 – 3.03%Ca, 2.54 – 3.31% Mg , 3.92 – 7.80 % Na ,1.37- 1.88 mg/kg Cu, 8.33 – 36.33% Se, 0.48 – 0.94 %Mn, 8.98 – 12.77% Moisture, 8.72–13.74% Ash, 8.87 – 13.37% Fat, 25.00 – 37.25% Fibre , 18.25 – 23.83% Carbohydrate, 21.66 – 31.59% Protein, 2084.0 – 2642.3mg/100g Flavonoids, 1094.0 – 1575.3 mg/100g Alkaloids, 974.7 – 1374.7 mg/100g Tannins, 0.88 – 1.02 mg/100g Saponins,1083.0 – 1308.3 mg/100g Phenols, 0.78 – 1.11 mg/g Hydrogen Cyanide, 186.0 – 243.33 μg/100g β- carotene, 27237 – 45410μg/100g Ascorbic acid, 642.7– 822.7μg/100g α- tocopherol and 272.67 – 404.67μg/100g Thiamine. Among the vegetables studied, fresh V. unguiculata had the highest levels of Zinc, Iron, Calcium, Magnesium, Sodium, Moisture, Fibre, β- carotene, Ascorbic acid, α- tocopherol, Thiamine while dried V. unguiculata had the highest levels of Ash. Fresh A. hybridus had the highest levels of Phenols and Fat whereas fresh S. nigrum had the highest levels of Carbohydrate, Protein, Alkaloid, Tannins, Flavonoids and Saponins. This study concludes that drying of the vegetables showed significant loss of all the tested parameters with exception of ash content (p<0.05). The study recommends the use of the vegetables in their fresh form and that shade drying can also be used to ensure the availability of the vegetables especially when off season; and among the studied vegetables, the cultivation of V.unguiculata should also be encouraged.