Biotransformation of Tyrosol into a Novel Valuable α-Galactoside with Increased Solubility and Improved Anti-inflammatory Activities

Herein, tyrosol [2-(4-hydroxyphenyl) ethanol], whichis rich inolive oil and red wine, was converted to a novel bioactive galactosideby enzymic glycosylation. The gene of & alpha;-galactosidase from Geobacillus stearothermophilus 23 was cloned andexpressed in Escherichia coli as catalyticallyactive inclusion bodies. The catalytically active inclusion bodiesefficiently catalyzed the galactosylation of tyrosol using eithermelibiose or raffinose family oligosaccharides as glycosyl donors,resulting in a glycoside with 42.2 or 14.2% yields. The glycosideproduct was purified and identified as p-hydroxyphenethyl & alpha;-d-galactopyranoside by mass spectrometry and NMRanalyses. The inclusion bodies can be recycled and reused for at least10 batch reactions of galactoside synthesis. Moreover, the galactosideshowed 11-fold increased water solubility and reduced cytotoxicityas compared to tyrosol. Also, it exhibited higher antioxidative andanti-inflammatory activities than tyrosol based on lipopolysaccharide-inducedactivated BV2 cells. These results provided important insights intothe application of tyrosol derivatives in functional foods.