Anti-inflammatory and antinociceptive effects of sinapyl alcohol and its glucoside syringin

In the present study, syringin, isolated by activity-guided fractionation of the ethyl acetate (EtOAc) extracts of the stem bark of Magnolia sieboldii, and sinapyl alcohol, the hydrolysate of syringin, were evaluated for anti-inflammatory and antinociceptive activities. Sinapyl alcohol (20, 30 mg/kg/day, p. o.) inhibited increased vascular permeability by acetic acid in mice and reduced acute paw edema by carrageenan in rats more so than syringin. When analgesic activity was measured using the acetic acid-induced writhing test and the hot plate test, sinapyl alcohol was much more potent than syringin in a mouse model. In addition, sinapyl alcohol more potently inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO), prostaglandin E2 (PGE2), and tumor necrosis factor (TNF)-alpha production by macrophages than syringin. Consistent with these observations, the expression levels of inducible NO Synthase (iNOS) and cyclooxygenase (COX)-2 was reduced by sinapyl alcohol in a concentration-dependent manner. These results suggest that the anti-inflammatory and antinociceptive effects of syringin after oral administration may be attributed to its in vivo transformation to sinapyl alcohol.