Comparative Evaluation of Iron Concentration and In vitro Bioavailability of Himalayan Kale and Spinach

Abstract

Iron (Fe) is an essential micronutrient involved in numerous physiological and biochemical processes, and increasing the availability of Fe-rich plant foods is important for improving dietary mineral nutrition. Himalayan kale (Brassica oleracea var. acephala) is a locally adapted leafy vegetable with potential as a source of essential minerals; however, variation in Fe concentration and bioavailability among its genotypes remains insufficiently characterised. The present study evaluated Fe concentration and relative in vitro Fe bioavailability in four selected Himalayan kale variants, H4, H5, H7 and H8. Dried leaf powders were subjected to wet acid digestion using nitric acid and perchloric acid (4:1), and Fe concentration was determined by atomic absorption spectrophotometry (AAS). A Caco-2 cell-based in vitro assay was additionally employed to assess relative Fe bioavailability. Spinach was included as a comparative leafy vegetable, while ferrous sulfate (FeSO₄) served as the reference control. Considerable variation in Fe concentration was observed, ranging from 5.83 to 16.58 ppm. H5 recorded the highest Fe concentration (16.58 ppm), followed by H7 (15.30 ppm), H4 (12.72 ppm) and H8 (5.83 ppm). H5 therefore contained approximately 2.84-fold more Fe than H8. The combined evaluation of Fe concentration and in vitro bioavailability identified H5 and H7 as promising variants, providing useful baseline information for nutritional characterisation and future utilisation of Himalayan kale in nutritional improvement and biofortification programmes.