Exploring gingerol glucosides with enhanced anti-inflammatory activity through a newly identified α-glucosidase (ArG) from Agrobacterium radiobacter DSM 30147.

Gingerols are phenolic biomedical compounds found in ginger (Zingiber officinale) whose low aqueous solubility limits their medical application. To improve their solubility and produce novel glucosides, an α-glucosidase (glycoside hydrolase) from Agrobacterium radiobacter DSM 30147 (ArG) was subcloned, expressed, purified, and then confirmed to have additional α-glycosyltransferase activity. After optimization, the ArG could glycosylate gingerols into three mono-glucosides based on the length of their acyl side chains. Compound 1 yielded 63.0 %, compound 2 yielded 26.9 %, and compound 3 yielded 4.37 %. The production yield of the gingerol glucosides optimally increased in 50 mM phosphate buffer (pH 6) with 50 % (w/v) maltose and 1000 mM Li at 40 °C for an 24-h incubation. The structures of purified compound 1 and compound 2 were determined as 6-gingerol-5-O-α-glucoside (1) and novel 8-gingerol-5-O-α-glucoside (2), respectively, using nucleic magnetic resonance and mass spectral analyses. The aqueous solubility of the gingerol glucosides was greatly improved. Further assays showed that, unusually, 6-gingerol-5-O-α-glucoside had 10-fold higher anti-inflammatory activity (IC value of 15.3 ± 0.5 μM) than 6-gingerol, while the novel 8-gingerol-5-O-α-glucoside retained 42.7 % activity (IC value of 106 ± 4 μM) compared with 8-gingerol. The new α-glucosidase (ArG) was confirmed to have acidic α-glycosyltransferase activity and could be applied in the production of α-glycosyl derivatives. The 6-gingerol-5-O-α-glucoside can be applied as a clinical drug for anti-inflammatory activity.