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Objective: Inspired by the traditionally clinical application of herb pair Zhimu - Huangbo to treat diabetes, a combination of plant ingredients, timosaponin B2 (TB-2) and berberine (BBR), was evaluated for their anti-diabetic efficacy and cooperative mechanisms. Methods: The efficacy and pharmacokinetics of orally administered TB-2 (33.3 mg/kg/day), BBR (66.7 mg/kg/day), and TB-2+BBR (100 mg/kg/day) were evaluated in spontaneously non-obese diabetic Goto-Kakizaki (GK) rats, and metformin (200 mg/kg/day) was used as a positive control. The comparative exposure of the parent drugs, timosaponin A3 (TB-2 metabolite), and M1–M5 (BBR metabolites) was quantified in the portal vein plasma (before hepatic disposition), liver, and systemic plasma (after hepatic disposition) of normal rats on single and combination treatments. Cooperative mechanism of TB-2 and BBR on intestinal absorption and hepatic metabolism was investigated in Caco-2 cells and primary hepatocytes, respectively. Results: After a 6-week experiment, non-fasting and fasting blood glucose levels and oral glucose tolerance test results showed that TB-2+BBR treatments (100 mg/kg/day) displayed significantly anti-diabetic efficacy in GK rats, comparable to that on metformin treatments. However, no significant improvement was observed on TB-2 or BBR treatments alone. Compared to single treatments, combination treatments led to the increased circulating levels of BBR by 107% in GK rats. In normal rats, the hepatic exposure of BBR, timosaponin A3, and M1–M5 was several hundred folds higher than their circulating levels. Co-administration also improved the levels in the plasma and liver by 41–114% for BBR, 141–230% for TB-2, and 12–282% for M1–M5. In vitro , the interaction between TB-2 and BBR was mediated by intestinal absorption, rather than hepatic metabolism. Conclusion: Combining TB-2 and BBR enhanced the anti-diabetic efficacy by increasing the in vivo variety of effective substances, including the parent compounds and active metabolites, and improving the levels of those substances through intestinal absorption. This study is a new attempt to assess the effects of combined plant ingredients on diabetes by scientifically utilizing clinical experience of an herb pair. [ABSTRACT FROM AUTHOR]

Gypenoside LVI and gypenoside XLVI are the major bioactive dammarane saponins from Gynostemma pentaphyllum . Gypenoside LVI, gypenoside XLVI, and their metabolite 2α-OH-protopanaxadiol (2α-OH-PPD) possess potent non-small cell lung carcinoma A549 cell inhibitory activity. A sensitive liquid chromatography tandem mass spectrometry method was developed and validated to study the pharmacokinetics of gypenoside LVI and XLVI, 2α-OH-PPD, metabolite 1 (M1), and metabolite 2 (M2) after administration of gypenosides or 2α-OH-PPD. Plasma samples from rats were protein precipitated with methanol. Analytes were detected by triple quadrupole MS/MS with an electrospray ionization source in the positive multiple reaction monitoring mode. The transition m / z 441.4 → 109.2 was selected to quantify gypenoside LVI and XLVI, and 2α-OH-PPD, because of the extensive conversion of the gypenosides to aglycone in the ionization source. M1 and M2 are isomers that shared the transition m / z 493.4 → 143.1. To avoid interference, the baseline separation of each analyte was performed on a SunFire C18 column with a gradient of acetonitrile (0.1% formic acid, v/v) and water (0.1% formic acid, v/v). The chromatographic run time was 10 min. The linearity was validated over a plasma concentration range from 2.00 to 2000 ng/mL for M1 and M2, and from 10.0 to 2000 for gypenosides LVI and XLVI, and 2α-OH-protopanaxadiol. The lower limits of quantification were 10.0, 10.0, 10.0, 2.00, and 2.00 ng/mL for gypenoside LVI, gypenoside XLVI, 2α-OH-PPD, M1, and M2, respectively, with acceptable intra-/inter-day precision and accuracy. The extraction recovery rates were >86.9% for each compound. No apparent matrix effect or instability was observed during each step of the bioanalysis. After full validation, this method was proved to be simple, fast, and efficient in analyzing large batches of plasma samples for the analytes. [ABSTRACT FROM AUTHOR]