Purification of Different Phenolic Compounds from Sorghum Bran on AB-8 Macroporous Resin and Protective Effects against Oxidative-stress-induced Erythrocyte Hemolysis
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Abstract:
Different types of phenols extracted from sorghum bran were purified on the AB-8 macroporous resin and then analyzed by high performance liquid chromatography (HPLC). The inhibitory effects of the phenols on human-erythrocyte hemolysis caused by 2,20-azobis-(2-amidinopropane) dihydrochloride (AAPH) were studied. The results showed that after purification on the AB-8 macroporous resin, phenol concentrations were in the following order: free phenols > insoluble bound esterified phenols > insoluble bound glycosidic phenols > soluble glycosidic phenols > soluble esterified phenols. According to the results of HPLC, the concentrations of 18 phenolic compounds were in the following order: insoluble bound esterified phenols > free phenols > insoluble bound glycosidic phenols > soluble esterified phenols > soluble glycosidic phenols. After the treatment with 200 μg/mL insoluble bound esterified, free, insoluble bound glycosidic, or soluble esterified phenols, the rate of AAPH-induced hemolysis of erythrocytes decreased to ~10%, which was close to that of the negative control group; the AAPH hemolysis rate of erythrocytes in the soluble glycosidic phenolic (200 μg/mL) treatment group was still 28.84%. Pretreatments with five different types of phenols effectively reduced the concentration of malondialdehyde (MDA), increased the glutathione/glutathione disulfide (GSH/GSSG) ratio in the AAPH-treated erythrocytes, and restored the erythrocytes to the normal state. The erythrocytes with relatively low superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were also protected. In conclusion, the different types of phenols from sorghum bran after purification on the AB-8 macroporous resin may protect human erythrocytes from the damage caused by AAPH-generated free radicals, and their intracellular antioxidant activity is related to their total phenolic content and composition of a mixture of phenolic compounds.
