Molecular modification of native coffee polysaccharide using subcritical water treatment: Structural characterization, antioxidant, and DNA protecting activities.

Polysaccharides are an abundant resource in coffee beans and have proved to show numerous bioactivities. Despite their abundance, their activities are not always satisfactory mostly due to their structure and large molecular size. Molecular modifications of native polysaccharides can overcome this problem. In this study, we used a novel and green method to modify native coffee polysaccharides using subcritical water (SCW) treatment. The SCW treatment was used at the temperature of 180°C-220°C and pressure of 30-60bar. The molecular and structural modification of the polysaccharides was confirmed using several techniques such as FT-IR, UV spectroscopy, XRD, and TGA. The antioxidant activity of the modified polysaccharides was evaluated using several chemical and Saccharomyces cerevisiae-based high throughput assays. The modified polysaccharides showed high antioxidant activities in all tested assays. Moreover, the polysaccharides showed high DNA protection activities. Therefore, SCW could be employed as a green solvent for molecular modification of polysaccharides.