Dimer Structures and Laccase-Catalyzed Polymerization Mechanism of Laccol in Fresh Rhus Succedanea Lacquer Sap

Laccase-catalyzed polymerization of laccol was promoted by a kneading process, and the molecular weight distribution and drying properties were examined. The laccol dimers were separated and purified by HPLC, and the chemical structures were characterized by IR, GC-MS, and NMR spectroscopy involving two-dimensional NMR measurements. Two sorts of C-C coupling, nuclear-nuclear (C-C) and nuclear-side chain (C-C), were found in the laccol dimer, which differ from the nuclear-side chain (C-O-C) couplings of urushiol and the only nuclear-nuclear (C-C) couplings of thitsiol. Based on these results, the properties of laccol lacquer film and the laccase-catalyzed polymerization mechanism of laccol are discussed.