Characterization of oxygenated metabolites of ginsenoside Rb1 in plasma and urine of rat

Oxygenated metabolites have been suggested as the major circulating metabolites of ginsenosides. In the current study, 10 oxygenated metabolites of ginsenoside Rb1 in plasma and urine of rat following iv dose were characterized by comparison with chemically synthesized authentic compounds as quinquenoside L16 (M1 and M2), notoginsenoside A (M3), ginsenoside V (M4 and M7), epoxyginsenoside Rb1 (M5 and M9), notoginsenoside K (M6), and notoginsenoside C (M8 and M10), 9 of which were detected as in vivo metabolites for the first time. After oral administration of ginsenoside Rb1, M3, M4, and M7 were observed as major circulating metabolites and presented in the bloodstream of rat for 24 h. Characterization of the exact chemical structures of these circulating metabolites could contribute greatly to our understanding of chemical exposure of ginsenosides after consumption of ginseng products and provide valuable information for explaining multiple bioactivities of ginseng products.

Structural identification of neopanaxadiol metabolites in rats by ultraperformance liquid chromatography/quadrupole-time-of-flight mass spectrometry

RATIONALE

Neopanaxadiol (NPD) is one of the major ginsenosides in Panax ginseng C. A. Meyer (Araliaceae) that has been suggested to be a drug candidate against Alzheimer's disease. However, few data are available regarding its metabolism in rats.

METHODS

In this study, a method of ultraperformance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UPLC/QTOFMS) was developed to identify major metabolites of NPD in the stomach, intestine, urine and feces of rats, with the aim of determining the main metabolic pathways of NPD in rats after oral administration.

RESULTS

UPLC/QTOFMS revealed two metabolites in the stomach of rats, one metabolite in the intestine and two metabolites in feces. One metabolite, named M2, was isolated and purified from rats feces, which was identified as (20S,22S)-dammar-22,25-epoxy-3β,12β,20-triol based on extensive NMR spectroscopy and mass spectrometry data. The main metabolites of NPD in rats were the products of epoxidation, dehydrogenation and hydroxylation. NPD was predominantly metabolized by 20,22-double-bond epoxidation and rearrangement to yield an expoxidation product (M2).

CONCLUSIONS

Based on the profiles of the metabolites, possible metabolic pathways of NPD in rats were proposed for the first time. This study provides new and available information on the metabolism of NPD, which is indispensable for further research on metabolic pathways of dammarane ginsengenins in vivo.

[Urine metabonomic study on long-term use of total ginsenosides in rats]

Due to its effect of systems regulation and promotion on body, Ginseng is always referred to be long-term used as a dietary supplement. But it was still unclear about its target of the tonic effects and also the side-effects long-term use may bring. Urine metabolomic method is suitable for long-term studies of pharmaco-dynamics, pharmacology and toxicology of traditional Chinese medicine because of its characteristics of non-invasive and monitoring the whole-body metabolism. This study was designed to detect the dynamic variation of rat urine metabolome along with a long-term administration of total ginsenosides using GC-TOF based metabolomic technology. Our result showed that either short-term or chronic administration of ginsenosides did not impact the rat urine metabolome significantly (as the PCA subgroup was not successful). By comparison, the short-term (1-3 w) dose of ginsenosides had the biggest metabolic influence including TCA cycle, catecholamines and neurotransmitter amino acids. Medium-term (6-10 w) dose had a gradually lower effect and long-term (27 w) dose almost had no effect. Our study indicates that both short and long-term administration of ginsenosides showed almost no obvious side-effect on the experimental animals.

Identification of 20(S)-protopanaxatriol metabolites in rats by ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry and nuclear magnetic resonance spectroscopy

20(S)-Protopanaxatriol (PPT), one of the aglycones of ginsenosides, has been shown to exert cardioprotective effects against myocardial ischemic injury. However, studies on PPT metabolism have rarely been reported. This study is the first to investigate the in vivo metabolism of PPT following oral administration by ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-Q/TOF-MS) and nuclear magnetic resonance (NMR) spectroscopy. The structures of the metabolites were identified based on the characteristics of their MS data, MS(2) data, and chromatographic retention times. A total of 22 metabolites, including 17 phase I and 5 phase II metabolites, were found and tentatively identified by comparing their mass spectrometry profiles with those of PPT. Two new monooxygenation metabolites, (20S,24S)-epoxy-dammarane-3,6,12,25-tetraol and (20S,24R)-epoxy-dammarane-3,6,12,25-tetraol, were chemicallly synthesized and unambiguously characterized according to the NMR spectroscopic data. The metabolic pathways of PPT were proposed accordingly for the first time. Results revealed that oxidation of (1) double bonds at Δ((24,25)) to form 24,25-epoxides, followed by rearrangement to yield 20,24-oxide forms; and (2) vinyl-methyl at C-26/27 to form corresponding carboxylic acid were the predominant metabolic pathways. Phase II metabolic pathways were proven for the first time to consist of glucuronidation and cysteine conjugation. This study provides valuable and new information on the metabolism of PPT, which is indispensable for understanding the safety and efficacy of PPT, as well as its corresponding ginsenosides.

[Simultaneous determination of ginsenosides and epimedium flavonoids in rat urine by HPLC-UV-ELSD]

OBJECTIVE

To develop and validate a HPLC-UV-ELSD method for the simultaneous determination of ginsenosides and epimedium flavonoids in rat urine after intravenous administration of Jiweiling freeze-dried powder.

METHOD

Chromatographic separation was performed on a C18 HPLC column, with gradient elution of acetonitrile and water as mobile phase. An UV detector was used at detection wavelength of 220 nm. An evaporative light scattering detector (ELSD) was used at drift tube temperature of 80 degrees C and gas pressure of 172.4 kPa.

RESULT

The calibration curves were linear over the investigated concentration ranges with all correlation coefficients higher than 0.998. The a intra- and inter-day RSD were less than 9.1% and the relative errors were verage extraction recoveries for all compounds were between 88.67% and 101.2%. The within the range of -11.58% to 10.89%.

CONCLUSION

The proposed method showed appropriate accuracy and selectivity and was successfully applied to the rat urine samples analysis of saponins and flavonoids after intravenous administration of Jiweiling freeze-dried powder, which may provide some references to the apprehension of the action mechanism and clinical application.

Characterization of pharmacokinetic profiles and metabolic pathways of 20(S)-ginsenoside Rh1 in vivo and in vitro

20(S)-Ginsenoside Rh1 is one of the important protopanaxatriol ginsenosides and has been reported to be the main hydrolysis product reaching the systemic circulation after oral ingestion of ginseng. However, its pharmacokinetic characteristics and metabolic fate have never been reported. The present study was therefore designed to elucidate its pharmacokinetic profiles and metabolic pathways both in vivo and in vitro. The absolute bioavailability of 20(S)-ginsenoside Rh1 in rats was only 1.01 %. Identification of metabolites showed that, after intragastrical administration of ginsenoside Rh1, two mono-oxygenated metabolites were detected from the urine, bile, liver tissue, and intestinal tract content, while the de-glucosylated product, 20(S)-protopanaxatriol, was only found in the contents of the intestinal tract. An in vitro incubation study confirmed that the CYP450-catalyzed mono-oxygenation, the intestinal bacteria mediated de-glucosylation, and the gastric acid mediated hydration reaction were the main metabolic pathways of 20(S)-ginsenoside Rh1. The presystemic metabolism as evidenced from this study may partially explain its poor bioavailability.

[Study on excretion of ginsenoside Rg2 in rats]

OBJECTIVE

To determine the ginsenoside Rg2 and study its excretion in bile, feces and urine of rat.

METHOD

Reversed phase high-performance liquid chromatographic (RP-HPLC) method with an ultra-violet detector (UVD) was performed at a detection wavelength of 203 nm and with a Dikma Diamonsil C18 column (4.6 mm x 250 mm, 5 microm), which the mobile phase was consisted of methanol-aq. 4% H3PO4 (65:35), for determination of the ginsenoside Rg2 in bile, feces and urine after administration of the ginsenoside Rg2 to rat at a tail vein single dose of 20 mg x kg(-1).

RESULT

The HPLC-UVD method fulfilled all the standard requirements of linearity, recovery, precision, and accuracy. After tail vein administration of the ginsenoside Rg2 to rat, the 5.5 hour cumulative biliary excretion rate and the 24-hour cumulative feces excretion rate of intact ginsenoside Rg2 were 27.2% and 22.6% of the administered dose, respectively. But intact ginsenoside Rg2 could not be detected in urine during this experimental period.

CONCLUSION

The bile and feces were the main excretion routs of the unchanged form after tail vein administration of the ginsenoside Rg2 to rat.

[Study on excretion of pseudo-ginsenoside GQ]

OBJECTIVE

To determine the pseudo-ginsenoside GQ (PGQ) in rat bile, feces and urine, and to study on the excretion of pseudo-ginsenoside GQ.

METHOD

Reverse phase high-performance liquid chromatography (RP-HPLC) method with an evaporative light-scattering detector (ELSD) was performed on Diamonsil C18 column (4.6 mm x 250 mm, 5 microm), and the mobile phase was consisted of methanol-water (24: 7) with flow rate of 1.0 mL x min(-1). ELSD parameters were set as follows: nitrogen gas pressure 3.0 bar, drift tube temperature 50 degrees C.

RESULT

The method fulfilled all the standard requirements of precision, accuracy and linearity. The main way of excretion of PGQ in rat administrated through sublingual vein was at the bile. The bile excretion ratio of PGQ was 41.60%, and feces excretion ratio was 9.97%. Only trace amount of PGQ was excreted in urine.

CONCLUSION

Almost all unchanged PGQ was excreted in bile, feces and urine.

Simultaneous determination of 17 ginsenosides in rat urine by ultra performance liquid chromatography–mass spectrometry with solid-phase extraction

A rapid analytical method for quantifying 17 ginsenosides in rat urine by ultra performance liquid chromatography (UPLC) coupled to electrospray ionization mass spectrometry (ESI-MS) is described. All analytes were extracted by solid-phase extraction optimized to obtain good recovery and quantified using digoxin as an internal standard. ESI-MS was optimized for different cone voltages at positive ionization mode to allow simultaneous analysis of all analytes in a relatively short time. Qualitative methodological considerations, including the linear range, precision, limit of quantification, limit of detection, recovery and sensitivity are also provided.

In vivo pharmacokinetic and metabolism studies of ginsenoside Rd

A high-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS(n)) method has been developed to determine ginsenoside Rd in human plasma and to identify its metabolites in rat urine. The plasma and urine samples were pretreated by solid phase extraction (SPE) prior to analyses. In this work, gentiopicroside was used as the internal standard. The lower limit of quantification (LLOQ) for Rd in human plasma was 3 ng/ml. The average half-life time in plasma was detected as 19.29 h, when 10 mg of ginsenoside Rd was administrated intravenously to the volunteers. Seven metabolites including three oxygenated, two combined and two hydrolyzed components were identified in rat urine samples by using LC-MS and MS-MS, when ginsenoside Rd administered either orally or intravenously.

[Determination of ginsenoside Rd and its metabolites in rat urine by LC-MS]

AIM

To study the metabolic pathways of ginsenoside Rd in rats.

METHODS

Urine samples were collected before and after 24 h of single oral administration of 150 mg and intravenous administration of 60 mg of ginsenoside Rd to six rats, separately. The samples were purified by SPE column and then were analyzed by liquid chromatography-ESI-mass spectrometry for putative metabolites.

RESULTS

Parent drug and its seven metabolites were identified in rat urine based on comparing total ion chromatograms of the blank with the metalolic urine as well as mass spectra. Its main metabolic pathways and possible structures are elucidated.

CONCLUSION

Oxidation, combination and deglucosylation were found to be the major metabolic pathway of ginsenoside Rd in rats.

High-performance liquid chromatography coupled with tandem mass spectrometry applied for metabolic study of ginsenoside Rb1 on rat

Liquid chromatography coupled with mass spectrometry and tandem mass spectrometry has been applied to investigate the in vivo metabolism of ginsenoside Rb(1) in rat. Both positive electrospray ionization mass spectrometry and negative electrospray ionization mass spectrometry were used to identify the Rb(1) and its metabolites in rat plasma, urine, and feces samples. Oxygenation and deglycosylation were found to be the major metabolic pathways of Rb(1) in rat. A total of nine metabolites were detected in urine and feces samples collected after intravenous and oral administration. Deglycosylated metabolism of Rb(1) generated other ginsenosides as the major metabolites, such as Rd, Rg(3) or F(2), Rh(2), or C-K. This result indicates that the ginsenoside Rb(1) has many pharmacological activities and could be used as a prodrug.

Inhibitory effect of ginsenoside Rb1 and compound K on NO and prostaglandin E2 biosyntheses of RAW264.7 cells induced by lipopolysaccharide

In this study, the antiinflammatory activities of ginsenoside Rb1, which is a main constituent of the root of Panax ginseng (Araliaceae), and of its metabolite compound K, as produced by human intestinal bacteria, on lipopolysaccharide (LPS)-induced RAW264.7 cells were investigated. Compound K potently inhibited the production of NO and prostaglandin E2 in LPS-induced RAW 264.7 cells, with IC(50) values of 0.012 and 0.004 mM, respectively. Compound K also reduced the expression levels of the inducible NO synthase (iNOS) and COX-2 proteins and inhibited the activation of NF-kB, a nuclear transcription factor. Compound K inhibited the NO level produced by iNOS enzyme activity in a cell-free system, but did not inhibit COX-1 and 2 activities. When ginsenoside Rb1 was orally administered to rats, compound K, but not ginsenoside Rb1, were excreted in their urine. These findings suggest that ginsenoside Rb1 can be transformed to compound K by intestinal bacteria, and compound K may be effective against inflammation.

Degradation of ginsenosides in humans after oral administration

Even though the degradation of ginsenosides has been thoroughly studied in animals and in vitro using acids, enzymes, and intestinal bacteria, knowledge concerning the systemic availability of ginsenosides and their degradation products in humans is generally lacking. Therefore, the attention in this article is focused on the identification of ginsenosides and their hydrolysis products reaching the systemic circulation in man. This is of great importance in understanding clinical effects, preventing herb-drug interactions, and optimizing the biopharmaceutical properties of ginseng preparations. Using a sensitive mass spectrometric method, which is specific for the identification of ginsenosides in complex biological matrices, the degradation pathway of ginsenosides in the gastrointestinal tract of humans could be elucidated following the oral administration of ginseng. Within the frame of a pilot study, human plasma and urine samples of two subjects were screened for ginsenosides and their possible degradation products. In general, the urine data coincided well with the plasma data. In both volunteers the same hydrolysis products, which are not originally present in the Ginsana extract (Pharmaton S.A., Lugano, Switzerland) ingested, were identified in plasma and urine. It was shown that two hydrolysis products of the protopanaxatriol ginsenosides, namely G-Rh1 and G-F1 may reach the systemic circulation. In addition, compound-K, the main intestinal bacterial metabolite of the protopanaxadiol ginsenosides, was detected in plasma and urine. These products are probably responsible for the action of ginseng in humans. In opposition to previous reports, G-Rb1 was identified in plasma and urine of one subject.