Phenolic Compounds from Chinese Sudangrass, Sorghum, Sorghum–Sudangrass Hybrid, and Their Antioxidant Properties

Abstract

Analysis of 33 varieties of three sorghum (Sorghum spp.) species cultivated in China showed that sudangrass (Sorghum sudanense Stapf) and sorghum–sudangrass hybrid [Sorghum bicolor (L.) Moench × S. sudanense] samples had higher concentrations of phenolic compounds (including total soluble phenol, proanthocyanidin, flavan-4-ols, anthocyanins, and five phenolic acids) than sorghum (S. bicolor) samples. In addition, the phenolic compounds were distributed extensively in the grain morphological fractions (including glumes, spikelets, caryopsis, endosperm, and embryo) of sudangrass and sorghum–sudangrass hybrid samples; however, they were mainly present in the glumes of sorghum except for total soluble phenol. The results indicated that sudangrass and sorghum–sudangrass hybrid samples in this study would be good sources of useful phenolic compounds such as anthocyanin (6.93 mg g−1 and 4.72 mg g−1) and proanthocyanidin (10.37 mg g−1 and 8.16 mg g−1) compared with sorghum samples (2.97 mg g−1 and 0.18 mg g−1 for anthocyanin and proanthocyanidin, respectively). Sudangrass and sorghum–sudangrass hybrid samples had higher antioxidant activities of 2,2¢-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) (230 and 108 μmol trolox equivalents [TE] g−1 for sudangrass; 258.5 and 130.3 μmol TE g−1 for sorghum–sudangrass hybrid) than sorghum samples (202.5 and 39.5 μmol TE g−1 for ABTS and DPPH, respectively). Thus, the sudangrass and sorghum–sudangrass hybrid samples in this study represented better commercial resources for nutritional and pharmaceutical purposes than sorghum samples because of higher antioxidant activities.