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

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.

Physicochemical properties and anthocyanin bioaccessibility of downy rose-myrtle powder prepared by superfine grinding

“…Generally, bioaccessibility is defined by the fraction of bioactive substance that is released from the food matrix after digestion and solubilized in the gut lumen for uptake across the intestinal mucosa. [3] The cell wall breakage ratio is a key factor limiting anthocyanin bioaccessibility during food digestion, since the approximate diameter of a plant cell ranges from 10 to 50 μm, [4] which is too small to be broken by chewing and grinding with teeth. Anthocyanins remaining within intact cells are inaccessible during upper gut digestion.…”

Assessment of nutritional water productivity and improvement strategies for traditional vegetables in South Africa

“…The nutrient content (iron, zinc, and vitamin A) for boiled vegetables were computed from the raw values using the United States Department of Agriculture nutrient retention factors (USDA, 2007) (Table 2A.1). We further assumed that around 45 % is lost due to limited bioavailability inside human bodies (Amagloh et al, 2017;Gupta et al, 2006). In addition, we calculated the amount of water required to meet human nutritional requirements per person (Box 2.…”

“…We assumed that 30% of β-carotene is lost during cooking (boiling) as mentioned by Laurie et al (2012a) and Van Jaarsveld et al (2006). For iron and zinc, around 50 % is lost due to cooking (boiling ≈ 5 %) and bioavailability (≈ 45 %) inside human bodies (Amagloh et al, 2017;Gupta et al, 2006).…”

Lemon Juice, Sesame Paste, and Autoclaving Influence Iron Bioavailability of Hummus: Assessment by an In Vitro Digestion/Caco-2 Cell Model

“…Other alternative techniques have been used to estimate iron bioaccessibility and bioavailability: the in vitro digestion preceding the iron dialysis, and the in vitro digestion coupled to the iron uptake by the Caco-2 cells [38]. The in vitro digestion/Caco-2 cell model was developed more than twenty years ago [39][40][41][42][43] and has gained much attention as a method for iron bioavailability prediction in the last decade [39,[44][45][46][47]. It was used to predict iron bioavailability from different food products, staple food crops, and forms of iron [48].…”