Preparation and Antioxidant Activityof Caffeic Acid Arabinoxylanesters from Corn Bran
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Abstract:
Arabinoxylan (CAX) was extracted from corn bran by the alkali-H2O2 method, and then caffeic acid (CA) was connected to CAX through ester bonding to yield caffeic acid arabinoxylanesters (CA-CAX). The structure of CA-CAX was characterized by FT-IR and H- and C-NMR, and its degree of substitution (DS) was determined by HPLC.CA-CAXs with different DSs (s represents degree of substitution) were obtained through using different amounts of CA, and their molecular weights were determined by high performance gel permeation chromatography(3.09×105, 3.36×105 and 3.68×105 g/mol for CAX, CA-CAX-0.27, CA-CAX-0.51 and CA-CAX-0.65, respectively). UV detection showed that CA-CAX-s had higher UVB absorption, and its aqueous solution exhibited significantly increased viscosity. Both the UV absorption and viscosity increased with an increase of CA content. In terms of DPPH free radical scavenging activity, the IC50 values of CA-CAX-0.27, CA-CAX-0.51 and CA-CAX-0.65 were 0.28, 0.13 and 0.12 mg/mL, respectively. Lipid peroxide detection of CA-CAX-0.65 at 4 mg/mL could reduce the content of malondialdehyde (MDA) from 120 ng/mL to the lowest value of 51.80 ng/mL. The analysis of antioxidant capacity index (ORAC) showed that the modified CA-CAX-s could delay the disappearance of fluorescence from 13 min to over 60 min, and also increased the ORAC value from 7 to 62.83.The antioxidant activity of CA-CAX was significantly higher than that of CAX, and a higher CA content led to a higher antioxidant activity of CA-CAX-s.
