Bioaccessibility and Speciation of Iron from Aqueous Extracts of Moringa oleifera Leaves

Investigating the different chemical species of soluble iron in food digests provides more relevant information on the nutritional potential of an iron-rich food. The objective of this study was to assess the bioaccessibility and speciation of iron from various aqueous extracts of Moringa (Moringa oleifera) leaves. Aqueous extracts were prepared from fresh and dried Moringa leaves using infusion and decoction methods. Spectrophotometric assays were performed to quantify inhibitors and enhancers of iron absorption in the extracts, bioaccessible iron, and its different chemical species. The highest contents of inhibitors (239.43 mg/L for polyphenols and 2.92 mg/L for phytates) and enhancers of iron absorption (1.58 mmol/L for carotenoids and 488.00 mg/L for ascorbic acid) were found in the 5-minute decoction extract of fresh leaves, and the lowest in all infusion extracts (27.34 mg/L for polyphenols, 0.50 mg/L for phytates, 0.15 mmol/L for carotenoids, and 86.00 mg/L for ascorbic acid). The percentages of bioaccessible iron were higher for decoction extracts (42.57–52.70%) compared to infusion extracts (33.89–36.44%). Ferrous iron was the dominant inorganic species of bioaccessible iron and was more concentrated in the digests of decoction extracts (1.32–4.85 mg/L). The highest content of organic iron (5.33 mg/L) was found in the digest of the 8-minute decoction extract of dried leaves. Drinking decoction extracts of fresh and dried Moringa leaves could be recommended to alleviate iron deficiency in vulnerable groups of the population living in areas where this plant can grow.