Proximate Composition, Mineral Profi le and Trypsin-Inhibitory Activity of West African Leafy Vegetables: Infl uence of Urea Micro-Dosing and Harvest Time

Abstract

In order to ensure the nutritional quality of leafy vegetables produced under intensive cultivation systems, the proximate composition, mineral profi le, and trypsin-inhibitory activity of three priority West African vegetable species (Amaranthus cruentus, Ocimum gratissimum, and Solanum macrocarpon) produced with urea micro-doses (20, 40, and 60 kg/ha) were compared with control leaves raised without urea. Plants were harvested three consecutive times to determine effects on nutrient and trypsin-inhibitory activity. Proximate and mineral compositions were mainly species-dependent (p<0.05) though the 60 kg/ha urea dose produced the signifi cantly (p<0.05) highest moisture content in leaves. Calcium, copper, iron, and zinc contents were signifi cantly (p<0.05) infl uenced by harvest time and its interaction with vegetable species. Furthermore, trypsin inhibition was signifi cantly (p<0.05) higher for the second and third leaf harvests, which suggests that initial wounding from the fi rst harvest enhanced synthesis of the inhibitor protein molecules.