Nutrient and total polyphenol contents of some dark green leafy vegetables, and estimation of their iron bioaccessibility using the In Vitro Digestion/Caco-2 Cell Model

Dark green leafy vegetables (DGLV) 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 sweetpotato cultivars including three orange-fleshed types with other DGLV commonly consumed DGLV in Ghana: cocoyam; corchorus; baobab; kenaf and moringa, using the in vitro digestion/Caco-2 cell model. Moringa had the highest amounts of iron absorption enhancers on an as-would-be-eaten basis, β-carotene (14,169 μg/100 g, 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 iron bioaccessibility. Baobab and the orange-fleshed sweetpotato with purplish young leaves contained the highest level of total polyphenols (1646.75 and 506.95 mg Gallic Acid Equivalents/100 g, p < 0.001, respectively). This suggests iron bioaccessibility in greens could not be inferred based on the mineral concentration. Based on the similarity of the iron bioaccessibility of the sweetpotato leaves and cocoyam leaf (widely-promoted “nutritious” DGLV in Ghana), the former greens have an added advantage of increasing dietary intake of provitamin A