Deglucuronidation of a flavonoid, luteolin monoglucuronide, during inflammation

In this study, we investigated whether luteolin monoglucuronide was convert ed to free aglycone during inflammation using human neutrophils stimulated with ionomycin/cytochalasin B and rats treated with lipopolysaccharide (LPS ). beta -Glucuronidase activity was assayed using 4-methylumbelliferyl-gluc uronide and methanol extracts of rat plasma containing luteolin monoglucuro nide. The released 4-methylumbelliferone, a fluorescent molecule, was quant ified by fluorometry. Deglucuronidation of luteolin monoglucuronide was exa mined by high-performance liquid chromatography (HPLC) analysis. HPLC analy ses showed that the supernatants obtained from neutrophils stimulated with ionomycin/cytochalasin B hydrolyzed luteolin monoglucuronide to free luteol in. beta -Glucuronidase activity in human serum from patients on hemodialys is increased significantly compared with that from healthy volunteers. The beta -glucuronidase activity in rat plasma increased after i.v. injection o f LPS. The ratio of luteolin to luteolin monoglucuronide in plasma of LPS-t reated rats also increased. These results suggest that during inflammation beta -glucuronidase is released from stimulated neutrophils or certain inju red cells and then deglucuronidation of flavonoids occurs.