The preparation and antioxidant activities of three phenyl-acylchitooligosaccharides

Chitooligosaccharides with two different molecular weights are acylated with three containing benzene carboxylic acids: salicylic acid (BHA), α-naphthylacetic acid (NAA) and indole-3-butyric acid (IBA) to obtain o-hydroxybenzoyl-chitooligosaccharide, α-naphthylacetyl-chitooligosaccharide, and 3-Indolebutyryl-chitooligosaccharide. The structure of the derivatives was characterized by FT-IR spectroscopy, ¹³C NMR spectroscopy and elemental analysis. According to several amide characteristic absorption peaks between 1750 cm^-1-1500 cm^-1 in the FT-IR spectrum, it can be determined that the target group has been successfully grafted. And there are obvious characteristic absorption peaks of aromatic ring at 900-650 cm^-1. The six chemical shifts of 98.02, 76.42, 74.83, 72.00, 60.39, 55.37 ppm in ¹³C NMR proved that the chitooligosaccharide did not destroy its own sugar ring structure during the reaction. The antioxidant activities of the derivatives, such as hydroxyl radical (·OH) scavenging ability, superoxide anion (O₂·^-) scavenging ability, reducing ability, and DPPH radical scavenging ability were investigated using various established systems. Comparing with chitooligosaccharide and containing benzene carboxylic acids, most derivatives have strong scavenging ability toward superoxide anions and DPPH radicals, and the clearance rate up to 47.44% and 80.27% separately. The reducing ability and hydroxyl free radical scavenging ability of the derivatives are only 0.032 Abs and 11.43%. The above results showed that the antioxidant activity of some derivatives was higher than that of chitooligosaccharide. The water solubility of the new derivatives was also greatly improved than that of containing benzene carboxylic acids. Therefore, the application of phenyl-acyl-chitooligosaccharide in antioxidants has laid a foundation, and has certain potential application value in the fields of medicine and agriculture and animal husbandry.