Nutrients and antinutritional factors at different maturity stages of selected indigenous African green leafy vegetables

A study was conducted to determine the effect of maturity stage on selected nutrients and anti-nutritional factors in selected indigenous African leafy vegetables namely Amaranths (Madiira Ex zim, and Madiira AM 38), African nightshade (Nduruma BG 16 and Olevolosi SS 49) and Spider plant. Vegetables were planted on plots and harvested at three maturity stages (21, 28 and 35 days). Chemical analyses were done to determine levels of vitamin C, iron and zinc and anti-antinutional factors (oxalate, phytate and nitrate).Vitamin C increased significantly (p<0.05) with maturity in all vegetables except African nightshade Nduruma BG 16. Vitamin C content was highest (162.7  1.2 mg/100g) in Spider plant and lowest (29.0  1.5 mg/100g) in African nightshade Olevolosi SS 49. Iron content increased significantly (p<0.05) at all maturity stages. Amaranths Madiira Ex zim had the highest iron concentration (999.0  3.7 mg/100g) while African nightshade Olevolosi SS 49 had the lowest value (231.1  1.5 mg/100g). Zinc content decreased with plant age although not significantly (p>0.05) between each stage. Zinc was highest (76.9  1.0 mg/100g) in Spider plant and lowest (44.8  0.7 mg/100g) in amaranths Madiira Ex zim. Oxalic acid concentration increased with plant age. African nightshade Nduruma BG 16 had lowest oxalic acid concentrations (28.7  0.0 mg/100g) while African nightshade Olevolosi SS 49 had highest value (60.9  0.9 mg/100g). Phytic acid increased significantly between stages of maturity in all varieties except in Spider plant. Highest phytic acid value was in amaranths Madiira AM 38 (0.9  0.0 mg/100g) while the lowest value (0.01  0.0 mg/100g) was in Spider plant Nitrate content decreased with plant age in all samples. Highest nitrate content was 86.1  1.1 mg/100g in Olevolosi SS 49 whereas lowest value was 45.8  0.6mg/100g in amaranths Madiira AM 38. The study concludes that nutrients and anti-nutritional factors vary with plant maturity and therefore the vegetables need to be harvested at 28 days.iii DECLARATION I, Teddy Mamboleo, do hereby declare to the Senate of Sokoine University of AgricultureEmbassy of Ireland and HORT-CRSP projec