Enzymatic synthesis of oligoesculin: structure and biological activities characterizations

The oligomerization of esculin, catalyzed by the laccase from Trametes versicolor , was realized in an attempt to improve the properties of this glycosidic coumarin. MALDI-TOF analyses showed a degree of oligomerization up to 9, whereas NMR spectra revealed the formation of C–C and C–O bridges, which involve both the phenolic and the glucosidic part of the coumarin. The solubility of oligomers is 189-fold higher than esculin’s solubility. Moreover, antioxidant properties of oligomers were correlated with their mass; the more the mass, the more the xanthine oxidase inhibitory activity and the radical scavenging activity are important. These experimental results were completed by in silico structural investigations, which suggested the preferential formation of C8–C8 linkages between esculin units during the oligomerization reaction.