The extraction, structural characterization and bioactivity of LCC from eucalyptus chips and its Pre-hydrolysis solution

In order to explore the potential differences in the structural characterisation of the LCC, LCC-AcOH and lignin fractions in eucalyptus chips and eucalyptus pre-hydrolysates, and the different biological activities caused by the different structural characterisation, we extracted and purified LCC, LCC-AcOH and lignin fractions from the two raw materials respectively. The structural analysis of the LCC, LCC-AcOH and lignin fractions was carried out with HPAEC, GPC, FT-IR, TGA, 2D HSQC NMR, and other tests. It then studied the scavenging rate of DPPH and hydroxyl radicals by these fractions, and the inhibition effect on S.aureus, E.coli and Bacillus subtilis, generally exploring the relationship between their antioxidant properties, inhibition properties and structure. The results showed this: the main linkages in eucalyptus LCC were PhGlc and gamma-Est, and that hot water pretreatment caused the gamma-Est in LCC to break and fail to recombine. The LCC extracted from the pre-hydrolysate contained only S type lignin structural units and were linked by beta-O-4' linkages, whereas the lignin of the other five fractions was GS-type lignin and the main linkages were beta-O-4', beta-beta' and beta-5' linkages. In addition, both EPHL-LCC-AcOH and EC-LCC-AcOH had better hydrophilic and biocompatible properties since they contained more acid-soluble lignin and carbohydrates, and both had good antioxidant and antibacterial properties respectively, which made them more potential for the development of new antioxidants and antibacterial agents.