Comparison of Content in Phenolic Compounds and Antioxidant Capacity in Grains of White, Red, and Black Sorghum Varieties Grown in the Mediterranean Area

Sorghum (Sorghum bicolor L.) is a gluten-free cereal with many varieties containing greater amounts of bioactive compounds than other grains. In this work, the phenolic composition and antioxidant capacity were compared in three sorghum varieties grown in the Mediterranean, consisting of different pericarp colors: white, red, and black. The qualitative and quantitative profiles of acidified aqueous methanol extracts of whole grain sorghum flours were elucidated through ultrahigh performance liquid chromatography (UHPLC) coupled to photodiode array (PDA) and ion trap time-of-flight (IT-TOF) mass spectrometry. The investigated sorghum varieties contained polyamines, such as spermidines, and polyphenolic compounds belonging to different classes: hydroxycinnamic acids, flavanols, flavones, and flavanones. Pyrano-flavanone-flavanols were detected only in the black sorghum. Precolumn and postcolumn 2,2′-diphenyl-1-picrylhydrazyl (DPPH)· radical scavenging assays to determine the main antioxidant compounds isolated from sorghum were developed. These results will further help develop sorghum varieties containing polyphenols relevant to the potential prevention of human diseases.