In Vitro Bioaccessibility and Bioavailability of Iron from Mature and Microgreen Fenugreek, Rocket and Broccoli

Abstract

Iron deficiency is a global epidemic affecting a third of the world's population. Current efforts are focused on investigating sustainable ways to improve the bioavailability of iron in plant-based diets. Incorporating microgreens into the diet of at-risk groups in populations could be a useful tool in the management and prevention of iron deficiency. This study analysed and compared the mineral content and bioavailability of iron from microgreen and mature vegetables. The mineral content of rocket, broccoli and fenugreek microgreens and their mature counterparts was determined using microwave digestion and ICP-OES. Iron solubility and bioavailability from the vegetables were determined by a simulated gastrointestinal in vitro digestion and subsequent measurement of ferritin in Caco-2 cells as a surrogate marker of iron uptake. Iron contents of mature fenugreek and rocket were significantly higher than those of the microgreens. Mature fenugreek and broccoli showed significantly (p < 0.001) higher bioaccessibility and low-molecular-weight iron than found in the microgreens. Moreover, iron uptake by Caco-2 cells was significantly higher only from fenugreek microgreens than the mature vegetable. While all vegetables except broccoli enhanced FeSO₄ uptake, the response to ferric ammonium citrate (FAC) was inhibitory apart from the mature rocket. Ascorbic acid significantly enhanced iron uptake from mature fenugreek and rocket. Microgreen fenugreek may be bred for a higher content of enhancers of iron availability as a strategy to improve iron nutrition in the populace.

Keywords: Microgreen; iron; mature; minerals; vegetables.

Figure 1

Cell viability of Caco-2 after exposure to digest vegetable Mature (MT) and Microgreen (MG) samples alone or with added ascorbic acid (AA) during digestion for 2 h. Results are presented as means ± SEM, n = 4. Data were analysed using a one-way ANOVA test. Different letters on top of bars indicate a significant difference: * (p ≤ 0.05), ** (p ≤ 0.01), *** (p ≤ 0.001) and **** (p ≤ 0.0001).

Figure 2

Iron uptake by Caco-2 cells from (a) Fenugreek, (b) Rocket, and (c) Broccoli mature (MT) and microgreen (MG) vegetables alone, with added ascorbic acid (AA) during digestion and vegetable samples with AA added during exposure to cells. The control treatment represents ferritin formation in Caco-2 cells in the presence of extract containing only the digestive enzymes. Results are presented as means ± SEM, n = 6. Data were analysed using a two-way ANOVA test. Different letters on top of bars indicate significant differences (p ≤ 0.05) between data in the same group. The differences between MT and MG groups of the same vegetables are denoted: * (p ≤ 0.05), ** (p ≤ 0.01), *** (p ≤ 0.001) and **** (p ≤ 0.0001).

Figure 3

Iron uptake by Caco-2 cells from vegetable digests. Cells were exposed to the digest samples with added 50 µM: (a) FeSO₄ (Fe(II)); and (b) FAC (Fe(III)). Results are presented as means of ± SEM n = 6. Data were analysed using a two-way ANOVA test between control and vegetable samples or among mature and microgreen samples. The differences between groups are denoted: * (p ≤ 0.05), ** (p ≤ 0.01) and **** (p ≤ 0.0001).

Figure 4

Phytic acid content (g/100 g) of the vegetable samples. Values are presented as means ± SEM, n = 6. Comparison of means of microgreens and mature vegetables were analysed using an independent samples t-test. The differences between the groups are denoted: * (p ≤ 0.05) and ** (p ≤ 0.01).