Partial structural characterization and antioxidant activity of a phenolic–xylan from Castanea sativa hardwood

Abstract : 4-O-Methylglucuronoxylans (MGX) were isolated from chestnut wood sawdust using two different procedures: chlorite delignification followed by the classical alkaline extraction step, and an unusual green chemistry process of delignification using phthalocyanine/H2O2 followed by a simple extraction with hot water. Antioxidant properties of both MGX were evaluated against the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) by electronic spin resonance (ESR). IC50 of water-extracted MGX was found to be less than 225 μg mL−1, in contrast with alkali-extracted MGX for which no radical scavenging was observed. Characterization of extracts by colorimetric assay, GC, LC–MS and NMR spectroscopy provided some clues to understanding structure–function relationships of MGX in connection with their antioxidant activity.