Feifei Du

Absorption and disposition of ginsenosides after oral administration of Panax notoginseng extract to rats

Panax notoginseng (Sanqi) is a cardiovascular herb containing ginsenosides that are believed to be responsible for the therapeutic effects of Sanqi. The aim of this study was to evaluate rat exposure to ginsenosides after oral administration of Sanqi extract and to identify the key factors affecting their absorption and disposition. Ginsenosides were administered to rats, either in the form of Sanqi extract or as pure chemicals. The ginsenosides Ra3, Rb1, Rd, Re, Rg1, and notoginsenoside R1 were the major saponins present in the herbal extract. Systemic exposure to ginsenosides Ra3, Rb1, and Rd after oral administration of the extract was significantly greater than that to the other compounds. Considerable colonic deglycosylation of the ginsenosides occurred, but the plasma levels of deglycosylated metabolites were low in rats. Poor membrane permeability and active biliary excretion are the two primary factors limiting systemic exposure to most ginsenosides and their deglycosylated metabolites. In contrast with other ginsenosides, biliary excretion of ginsenosides Ra3 and Rb1 was passive. Meanwhile, the active biliary excretion of ginsenoside Rd was significantly slower than that of other saponins. Slow biliary excretion, inefficient metabolism, and slow renal excretion resulted in long-circulating and thus relatively high exposure levels for these three ginsenosides. For these reasons, plasma ginsenosides Ra3, Rb1, and Rd were identified as pharmacokinetic markers for indicating rat systemic exposure to Sanqi extract. This is a systematic investigation of the absorption and disposition of ginsenosides from an herb, the information gained from which is important for linking Sanqi administration to its medicinal effects.

Plasma and Urinary Tanshinol from Salvia miltiorrhiza (Danshen) Can Be Used as Pharmacokinetic Markers for Cardiotonic Pills, a Cardiovascular Herbal Medicine

Cardiotonic pills are a type of cardiovascular herbal medicine. To identify suitable pharmacokinetic (PK) marker(s) for indicating systemic exposure to cardiotonic pills, we examined the in vivo PK properties of putatively active phenolic acids from the component herb Danshen (Radix Salviae miltiorrhizae). We also performed in vitro and in silico assessments of permeability and solubility. Several phenolic acids were investigated, including tanshinol (TSL); protocatechuic aldehyde (PCA); salvianolic acids A, B, and D; rosmarinic acid; and lithospermic acid. Plasma TSL exhibited the appropriate PK properties in dogs, including dose-dependent systemic exposure in area under concentration-time curve (AUC) and a 0.5-h elimination half-life. In rats, more than 60% of i.v. TSL was excreted intact into the urine. In humans, we found a significant correlation between the urinary recovery of TSL and its plasma AUC. The absorption rate and bioavailability of TSL were not significantly different whether cardiotonic pills were given p.o. or sublingually. The gender specificity in plasma AUC disappeared after body-weight normalization, but the renal excretion of TSL was significantly greater in women than in men. PCA was predicted to be highly permeable according to in vitro and in silico studies; however, extensive presystemic hepatic elimination and degradation in the erythrocytes led to extremely low plasma levels and poor dose proportionality. Integrated in vivo, in vitro, and in silico studies on the other phenolic acids showed poor gut permeability and nearly undetectable levels in plasma and urine. In conclusion, plasma and urinary TSL are promising PK markers for cardiotonic pills at the tested dose levels.

Systemic and cerebral exposure to and pharmacokinetics of flavonols and terpene lactones after dosing standardized Ginkgo biloba leaf extracts to rats via different routes of administration

Flavonols and terpene lactones are putatively responsible for the properties of Ginkgo biloba leaf extracts that relate to prevention and treatment of cardiovascular disease and cerebral insufficiency. Here, we characterized rat systemic and cerebral exposure to these ginkgo compounds after dosing, as well as the compounds’ pharmacokinetics.

Combinatorial Metabolism Notably Affects Human Systemic Exposure to Ginsenosides from Orally Administered Extract of Panax notoginseng Roots (Sanqi)

Ginsenosides are medicinal ingredients of the cardiovascular herb Panax notoginseng roots (Sanqi). Here, we implemented a human study (ChiCTR-ONC-09000603; www.chictr.org) to characterize pharmacokinetics and metabolism of ginsenosides from an orally ingested Sanqi-extract (a 1:10 water extract of Sanqi) and the human plasma and urine samples were analyzed by liquid chromatography-mass spectrometry. Plasma and urinary compounds derived from ginsenosides included: 1) intestinally absorbed ginsenosides Ra3, Rb1, Rd, F2, Rg1, and notoginsenoside R1; and 2) the deglycosylated products compound-K, 20(S)-protopanaxadiol, 20(S)-protopanaxatriol, and their oxidized metabolites. The systemic exposure levels of the first group compounds increased as the Sanqi-extract dose increased, but those of the second group compounds were dose-independent. The oxidized metabolites of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol represented the major circulating forms of ginsenosides in the bloodstream, despite their large interindividual differences in exposure level. The metabolites were formed via combinatorial metabolism that consisted of a rate-limiting step of ginsenoside deglycosylation by the colonic microflora and a subsequent step of sapogenin oxidation by the enterohepatic cytochrome P450 enzymes. Significant accumulation of plasma ginsenosides and metabolites occurred in the human subjects receiving 3-week subchronic treatment with the Sanqi-extract. Plasma 20(S)-protopanaxadiol and 20(S)-protopanaxatriol could be used as pharmacokinetic markers to reflect the subjects’ microbial activities, as well as the timely-changes and interindividual differences in plasma levels of their respective oxidized metabolites. The information gained from the current study is relevant to pharmacology and therapeutics of Sanqi.

Pulse gradient, large-volume injection, high-throughput ultra-performance liquid chromatographic/tandem mass spectrometry bioanalysis for measurement of plasma amrubicin and its metabolite amrubicinol

In this communication, we report the development of a new ultra-performance liquid chromatographic/tandem mass spectrometry (UPLC-MS-MS) assay for measurement of amrubicin (an anthracycline anti-cancer agent) and its active metabolite, amrubicinol, in plasma. The enhanced electrospray ionization signal intensity of the analytes achieved by modifying the mobile phase with formic acid was associated with improvement in the lower limit of quantification. These favorable effects were electrolyte concentration-dependent. In order to maximize assay throughput, we used methanol protein precipitation to prepare the plasma samples, and simplified sample preparation by injecting 40 microL of the supernatant containing methanol at 87.5% (v/v) directly onto the UPLC column without any intermediary solvent evaporation step. The large-volume injection of highly organic supernatant sample increased matrix and elutropic effects, but these drawbacks were respectively overcome by using a 5mM formic acid-modified mobile phase and a new pulse gradient method. To our knowledge, this is the first report successfully using large-volume injection of strong organic samples with UPLC-MS-MS bioanalysis. The pulse gradient elution also resulted in band compression and enhanced the robustness of the chromatography. The promising new approach illustrated herein is extremely straightforward to optimize, and may be used for UPLC-MS-MS bioanalytical assay of other compounds.

Intestinal Absorption and Presystemic Elimination of Various Chemical Constituents Present in GBE50 Extract, a Standardized Extract of Ginkgo biloba Leaves

The nature and level of systemic exposure to the active herbal constituents will profoundly affect their effects at action sites, which is fundamental in understanding their roles in the overall beneficial effects of a herbal medicine. The objective of this study is to gain a full picture of the systemic exposure to various putatively active ginkgo constituents after p.o. administration of GBE50 extract, a standardized extract of Ginkgo biloba leaves, to rats and understanding of the relevant mechanisms governing the intestinal absorption and presystemic elimination. To define the ginkgo compounds to be studied, literature informatics-guided chemical profiling revealed that GBE50 extract contained 72 ginkgo constituents, including terpene lactones, flavonols, flavones, an isoflavone, biflavones, flavanols, and carboxylic acids, at levels ranging from 0.01 to 55.3 mg/g. Among the ginkgo constituent groups were the terpene lactones and the flavonols that were significantly measurable in plasma after p.o. administration of GBE50 extract to rats. The intestinal absorption of terpene lactones appeared to be dictated by their intermediate membrane permeability, while the influences of MDR-1- and MRP-2- mediated intestinal efflux and the presystemic metabolism and biliary excretion might be relatively limited. Because of their deglycosylation absent in the small intestine and relatively slow presystemic elimination, many intact flavonol glycosides appeared in the rat plasma albeit with a limited extent of absorption. Colonic deglycosylation of the flavonol glycosides occurred and the glucuronides of flavonol aglycones were also measured in the plasma. Although some biflavones also had relatively high abundance in GBE50 extract, these ginkgo constituents were not measured in the rat plasma because of their poor solubility and poor permeability that hindered the intestinal absorption. The levels of the remaining ginkgo constituents in GBE50 extract were too low to be measured in the rat plasma. The current study enabled us to better understand the nature of systemic exposure to ginkgo compounds after p.o. administration of GBE50 extract and to more precisely implement multicomponent PK study of the extract.

Molecular mechanisms governing different pharmacokinetics of ginsenosides and potential for ginsenoside‐perpetrated herb–drug interactions on OATP1B3

Ginsenosides are bioactive saponins derived from Panax notoginseng roots (Sanqi) and ginseng. Here, the molecular mechanisms governing differential pharmacokinetics of 20(S)‐protopanaxatriol‐type ginsenoside Rg1, ginsenoside Re and notoginsenoside R1 and 20(S)‐protopanaxadiol‐type ginsenosides Rb1, Rc and Rd were elucidated.

Systemic Exposure to and Disposition of Catechols Derived from Salvia miltiorrhiza Roots (Danshen) after Intravenous Dosing DanHong Injection in Human Subjects, Rats, and Dogs

DanHong injection is a Danshen (Salvia miltiorrhiza roots)-based injectable solution for treatment of coronary artery disease and ischemic stroke. Danshen catechols are believed to be responsible for the injection’s therapeutic effects. This study aimed to characterize systemic exposure to and elimination of Danshen catechols in human subjects, rats, and dogs receiving intravenous DanHong injection. A total of 28 catechols were detected, with content levels of 0.002–7.066 mM in the injection, and the major compounds included tanshinol, protocatechuic aldehyde, salvianolic acid B, rosmarinic acid, salvianolic acids A and D, and lithospermic acid with their daily doses ≥10 μmol/subject. After dosing, tanshinol, salvianolic acid D, and lithospermic acid exhibited considerable exposure in human subjects and rats. However, only tanshinol had considerable exposure in dogs. The considerable exposure to tanshinol was due to its having the highest dose, whereas that to salvianolic acid D and lithospermic acid was due to their relatively long elimination half-lives in the human subjects and rats. Protocatechuic aldehyde and rosmarinic acid circulated in the bloodstream predominantly as metabolites; salvianolic acids A and B exhibited low plasma levels with their human plasma metabolites little or not detected. Tanshinol and salvianolic acid D were eliminated mainly via renal excretion. Elimination of other catechols involved hepatobiliary and/or renal excretion of their metabolites. Methylation was found to be the primary metabolism for most Danshen catechols and showed intercompound and interspecies differences in rate and degree in vitro. The information gained here is relevant to pharmacological and toxicological research on DanHong injection.

Renal Tubular Secretion of Tanshinol: Molecular Mechanisms, Impact on Its Systemic Exposure, and Propensity for Dose-Related Nephrotoxicity and for Renal Herb-Drug Interactions

Tanshinol has desirable antianginal and pharmacokinetic properties and is a key compound of Salvia miltiorrhiza roots (Danshen). It is extensively cleared by renal excretion. This study was designed to elucidate the mechanism underlying renal tubular secretion of tanshinol and to compare different ways to manipulate systemic exposure to the compound. Cellular uptake of tanshinol was mediated by human organic anion transporter 1 (OAT1) (Km, 121 μM), OAT2 (859 μM), OAT3 (1888 μM), and OAT4 (1880 μM) and rat Oat1 (117 µM), Oat2 (1207 μM), and Oat3 (1498 μM). Other renal transporters (human organic anion-transporting polypeptide 4C1 [OATP4C1], organic cation transporter 2 [OCT2], carnitine/organic cation transporter 1 [OCTN1], multidrug and toxin extrusion protein 1 [MATE1], MATE2-K, multidrug resistance-associated protein 2 [MRP2], MRP4, and breast cancer resistance protein [BCRP], and rat Oct1, Oct2, Octn1, Octn2, Mate1, Mrp2, Mrp4, and Bcrp) showed either ambiguous ability to transport tanshinol or no transport activity. Rats may be a useful model, to investigate the contribution of the renal transporters on the systemic and renal exposure to tanshinol. Probenecid-induced impairment of tubular secretion resulted in a 3- to 5-fold increase in the rat plasma area under the plasma concentration-time curve from 0 to infinity (AUC0–∞) of tanshinol. Tanshinol exhibited linear plasma pharmacokinetic properties over a large intravenous dose range (2–200 mg/kg) in rats. The dosage adjustment could result in increases in the plasma AUC0–∞ of tanshinol of about 100-fold. Tanshinol exhibited very little dose-related nephrotoxicity. In summary, renal tubular secretion of tanshinol consists of uptake from blood, primarily by OAT1/Oat1, and the subsequent luminal efflux into urine mainly by passive diffusion. Dosage adjustment appears to be an efficient and safe way to manipulate systemic exposure to tanshinol. Tanshinol shows low propensity to cause renal transporter-mediated herb-drug interactions.

Oral bioavailability and brain penetration of (−)-stepholidine, a tetrahydroprotoberberine agonist at dopamine D1 and antagonist at D2 receptors, in rats

Background and purpose:  (−)‐Stepholidine has high affinity for dopamine D1 and D2 receptors. The aims of the present study were to examine the oral bioavailability and brain penetration of (−)‐stepholidine and to gain understanding of mechanisms governing its transport across the enterohepatic barrier and the blood–brain barrier.