Provitamin A Carotenoids, Tocopherols, Ascorbic Acid and Minerals in Indigenous Leafy Vegetables from Tanzania

Abstract

The essential micronutrients in indigenous leafy vegetables (ILVs) could substantially contribute to the micronutrient supply in rural communities in Tanzania, but concentrations differ between species. Provitamin A carotenoids, tocopherols, ascorbic acid, minerals, and phytate were analysed in 13 different species using HPLC-, ICP-OES, and photometric techniques. Eight of the 13 ILVs, including Amaranthus ssp. and Sesamum angustifolium, had high β-carotene concentrations (2.91–4.84 mg/100 g fresh weight), which could provide ≥50% of vitamin A’s recommended nutrient intake (RNI). Six ILVs including Cleome hirta and Sonchus luxurians had high iron contents (34.5–60.4 mg/100 g, >50% RNI); Amaranthus ssp. represented the ILV with high calcium, magnesium and zinc contents (85%, 207% and 21% of RNI per 100 g); Cleome hirta and Cleome gynandra had high ascorbic acid contents (>15 mg/100 g, 34–35% of RNI), while Sesamum angustifolium was the only ILV with a high tocopherol content (7.34 mg α-TE/100 g). The highest phytate concentration was found in Amaranthus ssp., which could negatively affect its role as a very good source of minerals. Results indicate that the analysed ILVs could make a substantial contribution to the vitamin A and iron supply in the diets of rural Tanzanian populations.

Keywords

• leafy vegetables
• micronutrients
• carotenoids
• nutrient intake
• Tanzania