Comparative antioxidant activity of nanoscale lignin prepared by a supercritical antisolvent (SAS) process with non-nanoscale lignin

Abstract

► Using supercritical antisolvent method to successfully prepare nanoscale lignin. ► Micronization process had not induced lignin degradation and structure change. ► Radical scavenging capacities of the nanoscale lignin were obviously improved. Nowadays, lignin antioxidant study is a hot spot. But some properties of lignin make it hard for a wide range of application. To improve lignin antioxidant activity, we employed supercritical antisolvent (SAS) method for preparation of nanoscale lignin (0.144 ± 0.03 μm) using acetone as a solvent and supercritical carbon dioxide as an antisolvent. The nanoscale lignin was characterised by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). The results showed that SAS process did not result in lignin degradation or chemical structure change. Due to solubility increase, many antioxidant parameters of the nanoscale lignin were obviously enhanced, including DPPH radical scavenging activity, superoxide radical scavenging activity and reducing power. As an antioxidant, the nanoscale lignin was a better material than the non-nanoscale lignin. Our study was to promote the lignin application in animal husbandry, pharmaceutical and food processing industries.