Gallyl chitooligosaccharides inhibit intracellular free radical-mediated oxidation

► Chitooligosaccharides derivative (COS) were conjugated with gallic acid to obtain a novel antioxidant (G-COS) as a nutraceutical ingredient. ► The free radical scavenging properties of novel G-COS derivative were analysed by ESR spectrometer. ► Intra cellular antioxidant activities were also investigated on SW1353 cell line. ► In conclusion, G-COS can be used as a free radical scavenger in the prevention and treatment of osteoarthritis.