Nutritional and phytogeriatological studies of three varieties of Gnetum africanum (‘afang’)

Abstract

Three varieties of Gnetum africanum viz. the Asutan, Oron and Ikom, commonly consumed in the Southern parts of Nigeria, were assayed for their proximate nutritional composition and fibre characteristics as they related to age of the leaves. Nutritionally, the Asutan variety was significantly ( p<0.05) superior to the other two. It had the highest levels of ash, protein, lipid and highest caloric value. It also had the lowest contents of antinutrients such as tannins, oxalates, glucosinolates and hydrocyanic acid, which were all below documented toxic levels. Bioassay using albino rats confirmed the high nutritional value of the Asutan variety. Phytogeriatological assay showed that, in the Asutan variety, protein content, crude fibre, fibre length and fibre width increased with age of the plant, peaking at 6–12 months. There was positive correlation between crude fibre, fibre length and age ( p<0.05) whereas crude protein, in vitro digestibility and fibre width were negatively correlated with age. The findings are discussed with special reference to the possible contribution of G. africanum to the nutrient requirements of man in health and disease. A suggestion is also made for the selective cultivation of the Asutan variety over the other two.