Nutrient and Total Polyphenol Contents of Dark Green Leafy Vegetables, and Estimation of Their Iron Bioaccessibility Using the In Vitro Digestion/Caco-2 Cell Model.

Francis Amagloh,Tatiana Christides,Richard Mcbride,Richard Atuna,Edward Carey

doi:10.3390/foods6070054

Abstract

Dark green leafy vegetables (DGLVs) are considered as important sources of iron and vitamin A. However, iron concentration may not indicate bioaccessibility. The objectives of this study were to compare the nutrient content and iron bioaccessibility of five sweet potato cultivars, including three orange-fleshed types, with other commonly consumed DGLVs in Ghana: cocoyam, corchorus, baobab, kenaf and moringa, using the in vitro digestion/Caco-2 cell model. Moringa had the highest numbers of iron absorption enhancers on an “as-would-be-eaten” basis, β-carotene (14169 μg/100 g; p < 0.05) and ascorbic acid (46.30 mg/100 g; p < 0.001), and the best iron bioaccessibility (10.28 ng ferritin/mg protein). Baobab and an orange-fleshed sweet potato with purplish young leaves had a lower iron bioaccessibility (6.51 and 6.76 ng ferritin/mg protein, respectively) compared with that of moringa, although these three greens contained similar (p > 0.05) iron (averaging 4.18 mg/100 g) and β-carotene levels. The ascorbic acid concentration of 25.50 mg/100 g in the cooked baobab did not enhance the iron bioaccessibility. Baobab and the orange-fleshed sweet potato with purplish young leaves contained the highest levels of total polyphenols (1646.75 and 506.95 mg Gallic Acid Equivalents/100 g, respectively; p < 0.001). This suggests that iron bioaccessibility in greens cannot be inferred based on the mineral concentration. Based on the similarity of the iron bioaccessibility of the sweet potato leaves and cocoyam leaf (a widely-promoted “nutritious” DGLV in Ghana), the former greens have an added advantage of increasing the dietary intake of provitamin A.

Highlights

It is generally accepted that dark green leafy vegetables (DGLVs) are important sources of micronutrients such as iron and vitamin A
Moringa had the highest levels of β-carotene and ascorbic acid
Baobab had the highest levels of calcium and total polyphenols

Summary

Introduction

It is generally accepted that dark green leafy vegetables (DGLVs) are important sources of micronutrients such as iron and vitamin A. On the basis of compositional data, DGLVs were reported to contribute about 19–39% of iron and 42–68% of vitamin A [1] in the diets of rural South. Iron and vitamin A deficiencies are perennial malnutrition problems in developing countries where DGLVs are important food ingredients [2,3]. Foods 2017, 6, 54 possibly with a high concentration of micronutrients such as iron and β-carotene (provitamin A), are the greens. Cercamondi and co-workers [4] reported that sauce prepared from amaranth (Amaranthus cruentus) or Jew’s mallow/corchorus (Corchorus olitorius) and examples of DGLVs, eaten with a thick maize paste by young Burkinabe women, did not increase the amount of iron absorbed. The bioaccessibility of minerals from food may not solely depend on their concentration, and on other constituents in the food

Objectives

Methods

Results

Discussion

Conclusion