Assessment of Bioactive Profile of Sorghum Brans under the Effect of Growing Conditions and Nitrogen Fertilization

Sorghum bicolor (L.) Moench is an increasingly important crop grown in many countries as a food source due to its excellent nutritional value, drought and pest resistance, and gluten-free properties. In this study, the bioactive profiles and antioxidant potentials of brans of six sorghum varieties were evaluated using spectrophotometric methods. The effects of weather and environmental conditions and different nitrogen nutrition were also evaluated. The bran of red varieties contained a higher amount of polyphenols and tannins and exhibited higher antioxidant capacities than the bran of white varieties, with the exception of one red genotype. The highest total polyphenol contents were measured in samples from two red varieties (Zádor, Alföldi1) with 1084.52 ± 57.92 mg 100 g −1 GAE and 1802.51 ± 121.13 mg 100 g −1 GAE values, respectively, while condensed tannin content varied between 0.50 mg g −1 and 47.79 mg g −1 in sorghum brans. Red varieties showed higher antioxidant activities/capacities with 70–281 µmol TE g −1 and 71–145 µmol TE g −1 for DPPH and TEAC. Correlation analysis showed a strong interaction between DPPH, TEAC, and the amounts of polyphenols and tannins, but not with FRAP values. In conclusion, red-colored varieties are a good source of polyphenols, but seed color alone is not enough to determine the nutritional value of a genotype, and the environmental conditions greatly affect the bioactive profile of sorghum.