Seed Coat Color-Mediated Differences in Nutritional Composition and Antioxidant Activity of Mung Bean

The mung bean (Vigna radiata) is rich in nutrients and bioactive compounds and is valuable for its antioxidant content in functional food development. However, mung bean seed coats are discarded or used as a low-value feed owing to their coarse texture. Here, 12 homozygous mung bean lines with different seed coat colors were selected from six recombinant inbred lines. The seed coats and cotyledons were separated and quantitatively analyzed for protein, starch, dietary fiber, polyphenols, flavonoids, vitexin, isovitexin, and antioxidant activities using standard chemical assays and HPLC, followed by statistical analysis and principal component analysis. The cotyledons contained more protein (26.97–28.34%) and starch (50.40–56.25%), whereas the seed coat contained more dietary fiber (74.17–79.93 g/100 g) and bioactive compounds. Polyphenolic compounds were significantly higher in the seed coat than in the cotyledons (p < 0.05) and were positively correlated with seed coat darkness, indicating that the black mung bean had higher bioactive functions. This study provides evidence for mung bean variety improvement and functional food development.