In vitro assessment of the glucose-lowering effects of berberrubine-9-O-ß-D-glucuronide, an active metabolite of berberrubine.

Berberrubine (BRB) is the primary metabolite of berberine (BBR) that has shown a stronger glucose-lowering effect than BBR in vivo. On the other hand, BRB is quickly and extensively metabolized into berberrubine-9-O-ß-D-glucuronide (BRBG) in rats after oral administration. In this study we compared the pharmacokinetic properties of BRB and BRBG in rats, and explored the mechanisms underlying their glucose-lowering activities. C57BL/6 mice with HFD-induced hyperglycemia were administered BRB (50 mg·kg-1·d-1, ig) for 6 weeks, which caused greater reduction in the plasma glucose levels than those caused by BBR (120 mg·kg-1·d-1) or BRB (25 mg·kg-1·d-1). In addition, BRB dose-dependently decreased the activity of α-glucosidase in gut of the mice. After oral administration of BRB in rats, the exposures of BRBG in plasma at 3 different dosages (10, 40, 80 mg/kg) and in urine at different time intervals (0-4, 4-10, 10-24 h) were dramatically greater than those of BRB. In order to determine the effectiveness of BRBG in reducing glucose levels, we prepared BRBG from the urine pool of rats, and identified and confirmed it through LC-MS-IT-TOF and NMR spectra. In human normal liver cell line L-O2 in vitro, treatment with BRB or BRBG (5, 20, 50 µmol/L) increased glucose consumption, enhanced glycogenesis, stimulated the uptake of the glucose analog 2-NBDG, and modulated the mRNA levels of glucose-6-phosphatase and hexokinase. However, both BBR and BRB improved 2-NBDG uptake in insulin-resistant L-O2 cells, while BRBG has no effect. In conclusion, BRB exerts a stronger glucose-lowering effect than BBR in HFD-induced hyperglycemia mice. Although BRB significantly stimulated the insulin sensitivity and glycolysis in vitro, BRBG may have a greater contribution to the glucose-lowering effect because it has much greater system exposure than BRB after oral administration of BRB. The results suggest that BRBG is a potential agent for reducing glucose levels.

Sensitive analysis and pharmacokinetic study of the isomers paeoniflorin and albiflorin after oral administration of Total Glucosides Of White Paeony Capsule in rats.

A sensitive and reliable method using liquid chromatography tandem mass spectrometry (LC-MS/MS) was established for the simultaneous assay of paeoniflorin and albiflorin in bio-samples of rats after liquid-liquid extraction with ethylacetate. For the first time, the developed method was validated and successfully applied to the pharmacokinetics study of paeoniflorin and albiflorin after oral administration of Total Glucosides Of White Paeony Capsule (TGP). Relative to the intravenous injection, the absolute bio-availabilities of paeoniflorin and albiflorin were 2.8 and 1.7%, while their excretion in feces was 43.06 and 40.87%, respectively. Both paeoniflorin and albiflorin showed dose-dependent exposure in plasma, with a half-life of approximately 1.8h. No significant differences were observed between a single equal dose of paeoniflorin or albiflorin and that of TGP for the pharmacokinetic parameters, including AUC, T1/2 and Cmax. Paeoniflorin and albiflorin were exposed at high levels in immune relevant organ/tissues, such as the spleen, thymus and bone, which could facilitate immuno-regulatory activities.