UFLC–MS/MS determination and pharmacokinetic studies of six Saikosaponins in rat plasma after oral administration of Bupleurum Dropping Pills

Comparative permeability of three saikosaponins and corresponding saikogenins in Caco-2 model by a validated UHPLC-MS/MS method

Saikosaponins (SSs) are the main active components extracted from Bupleuri Radix (BR) which has been used as an important herbal drug in Asian countries for thousands of years. It has been reported that the intestinal bacteria plays an important role in the in vivo disposal of oral SSs. Although the deglycosylated derivatives (saikogenins, SGs) of SSs metabolized by the intestinal bacteria are speculated to be the main components absorbed into the blood after oral administration of SSs, no studies have been reported on the characteristics of SGs for their intestinal absorption, and those for SSs are also limited. Therefore, a rapid UHPLC-MS/MS method was developed to investigate and compare the apparent permeability of three common SSs (SSa, SSd, SSb₂) and their corresponding SGs (SGF, SGG, SGD) through a bidirectional transport experiment on Caco-2 cell monolayer model. The method was validated according to the latest FDA guidelines and applied to quantify the six analytes in transport medium samples extracted via liquid-liquid extraction (LLE). The apparent permeability coefficient (P _app ) determined in this study indicated that the permeability of SGs improved to the moderate class compared to the corresponding parent compounds, predicting a higher in vivo absorption. Moreover, the efflux ratio (ER) value demonstrated an active uptake of SSd and the three SGs, while a passive diffusion of SSa and SSb₂.

Efficient and clean preparation of rare prosaikogenin D by enzymatic hydrolysis of saikosaponin B2 and response surface methodology optimization

Prosaikogenin D, a rare secondary saponin in Radix Bupleuri, has much higher in vivo bioactivities than its original glycoside saikosaponin B₂. Its preparation methods, such as conventional acid hydrolysis and column chromatograph, are unfriendly to environment with serious pollution and undesired products. The aim of this study was to establish an efficient and clean approach for convenient preparation of this rare steroid saponin based on the enzymatic hydrolysis. Cellulase was selected from four commercial enzymes due to its higher hydrolysis performance. Then the hydrolysis conditions were optimized by response surface methodology after preliminary investigation on affecting factors by single-factor experiments. The reaction system was constructed by 100 μg/mL of saikosaponin B₂ and 8.00 mg/mL of cellulase, which was incubated in HAc-NaAc buffer (pH 4.7) at 60 °C for 33 h. Consequently, a high conversion ratio of the substrate has been achieved at 95.04 %. The newly developed strategy is an efficient and clean approach for the preparation of prosaikogenin D and it is a promising technology in industrial application.

Localization of malonyl and acetyl on substituted saikosaponins according to the full-scan mass spectra and the fragmentation of sodium-adduct ions in the positive mode

RATIONALE

Discriminating between aglycone-substituted and saccharide-substituted saikosaponins by liquid chromatography/tandem mass spectrometry (LC/MSⁿ ) is a long-standing issue that is still to be resolved. It is necessary to characterize the two types of substituted saikosaponins taking into consideration the potential significant difference in their bioactivity.

METHODS

Taking the substituents malonyl and acetyl as examples, we developed a MS strategy to discriminate between the aglycone-substituted and saccharide-substituted saikosaponins through comparing their Y₀  - nH₂ O (n = 1-2) ions from the protonated molecules in the full-scan mass spectra and their B ions in the MS² spectra of sodium-adduct molecules in the positive mode.

RESULTS

The deprotonated molecules of the aglycone-substituted saikosaponins presented similar fragmentation patterns to those of saccharide-substituted ones in the negative mode, which could not discriminate whether the substitutes were located on the aglycone or the saccharide. In contrast, the Y₀  - nH₂ O (n = 1-2) ions containing or no substituent were observed respectively in the mass fragmentation of the protonated molecules of aglycone-substituted or saccharide-substituted saikosaponins in the positive mode. In addition, the B ions containing or no substituent were observed respectively in the mass fragmentation of the sodium-adduct molecules of the saccharide-substituted or aglycone-substituted saikosaponins in the positive mode. Two aglycone-malonylated saikosaponins were reported for the first time.

CONCLUSIONS

Whether the substituents were located on the aglycone or the saccharide could be determined according to the Y₀  - nH₂ O (n = 1-2) ions from the protonated molecules in the full-scan mass spectra and the B ions in the MS² spectra of sodium-adduct molecules in the positive mode. Our results have updated the mass fragmentation patterns of substituted saikosaponins, which is helpful for the quality control of pharmaceutical preparations containing saikosaponins. More importantly, this MS strategy should be able to be extended to characterize other substituted saponins of bioactive significance in future studies.

Pharmacokinetic Study of Main Active Components of Rumex nepalensis Spreng Extract in Rats Plasma by UPLC-MS/MS

Background:

The Rumex nepalensis Spreng (RNS) is a traditional Chinese medicine containing rich anthraquinones. However, through proper investigation we have found that there were no reports on the pharmacokinetics of RNS extract in rats. </P><P> Objective: We study on the pharmacokinetic behaviors of emodin, chrysophanol and physcion after oral administration of RNS extract in rat to achieve a better understanding of further clinical application and conduct the preparation development of the herb.

Methods:

In the present study, a sensitive and rapid ultra-fast liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed and validated to determine the three anthraquinones such as chrysophanol, emodin and physcion in rat plasma along with danthron as the internal standard (IS). The analytes and IS were separated on an Acquity UPLC HSS T3 column (100 mm × 2.1 mm, 1.8 µm) by using the mobile phase of water with 3 mM ammonium acetate and acetonitrile as gradient elution at a flow rate of 0.4 mL min -1. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) by multiple reactions monitoring (MRM) of the transitions at m/z 253.1 → 225.0 for chrysophanol, 269.0 → 224.9 for emodin, 282.7→ 240.0 for physcion and m/z 239.0 → 211.0 for IS. The limit of detection and lower limit of quantification were both 2 ng mL -1 in rat plasma.

Results:

Good linearity of this method was obtained in the range of 2-1000 ng mL -1 , and the correlation coefficient was greater than 0.990. According to regulatory guidelines, the established method was fully validated, and the results were within acceptable limits.

Conclusion:

The validated method was successfully applied into a pharmacokinetic study of orally administered RNS extract in rats.

UPLC-MS/MS Method for the Determination of 14 Compounds in Rat Plasma and Its Application in a Pharmacokinetic Study of Orally Administered Xiaoyao Powder

Xiaoyao Powder (XYP), a common Chinese medicine, comprises eight traditional Chinese herbs and has been widely used clinically to treat liver damage and mental disorders. An ultra-performance liquid chromatography–tandem mass spectrometry method was developed to investigate the pharmacokinetics of 14 compounds (albiflorin, paeoniflorin, ferulic acid, senkyunolide I, quercetin, isoliquiritigenin, atractylenolide III, ligustilide, atractylenolide II, liquiritin, liquiritigenin, saikosaponin c, glycyrrhizic acid, and saikosaponin a) in XYP. Naringenin was used as the internal standard. The compounds were separated using an ACQUITY UPLC^TM BEH C18 column (1.7 μm, 50 × 2.1 mm) with a mobile phase consisting of acetonitrile and 0.1% formic acid in water at a flow rate of 0.3 mL/min. Detection was performed on a triple-quadrupole tandem mass spectrometer using multiple reaction monitoring and an electrospray ionization source in both positive and negative ionization modes. All calibration curves exhibited good linearity (r² > 0.9974) over the measured ranges. The intra- and inter-day precisions were within 12%, and the accuracy ranged from 89.93% to 106.64%. Extraction recovery and matrix effect results were satisfactory. The method was successfully applied in a pharmacokinetic study of the 14 compounds in rat plasma after the oral administration of XYP.

A Highly Sensitive Immunochromatographic Strip Test for Rapid and Quantitative Detection of Saikosaponin d

A quantitative lateral-flow immunoassay using gold nanoparticles (AuNPs) conjugated with a monoclonal antibody (MAb) against saikosaponin d (SSd) was developed for the analysis of SSd. The AuNPs were prepared in our laboratory. The AuNPs were polyhedral, with an average diameter of approximately 18 nm. We used the conjugation between AuNPs and MAbs against SSd to prepare immunochromatographic strips (ICSs). For the quantitative experiment, the strips with the test results were scanned using a membrane strip reader, and a detection curve (regression equation, y = -0.113ln(x) + 1.5451, R² = 0.983), representing the averages of the scanned data, was obtained. This curve was linear from 96 ng/mL to 150 μg/mL, and the IC₅₀ value was 10.39 μg/mL. In this study, we bring the concept ofPOCT (point-of-care testing) to the measurement of TCM compounds, and this is the first report of quantitative detection of SSd by an ICS.

Interaction between Saikosaponin D, Paeoniflorin, and Human Serum Albumin

Saikosaponin D (SSD) and paeoniflorin (PF) are the major active constituents of Bupleuri Radix and Paeonia lactiflora Pall, respectively, and have been widely used in China to treat liver and other diseases for many centuries. We explored the binding of SSD/PF to human serum albumin (HSA) by using fluorospectrophotometry, circular dichroism (CD) and molecular docking. Both SSD and PF produced a conformational change in HSA. Fluorescence quenching was accompanied by a blue shift in the fluorescence spectra. Co-binding of PF and SSD also induced quenching and a conformational change in HSA. The Stern-Volmer equation showed that quenching was dominated by static quenching. The binding constant for ternary interaction was below that for binary interaction. Site-competitive experiments demonstrated that SSD/PF bound to site I (subdomain IIA) and site II (subdomain IIIA) in HSA. Analysis of thermodynamic parameters indicated that hydrogen bonding and van der Waals forces were mostly responsible for the binary association. Also, there was energy transfer upon binary interaction. Molecular docking supported the experimental findings in conformation, binding sites and binding forces.

Pharmacokinetic parameters of three active ingredients hederacoside C, hederacoside D, and ɑ-hederin in Hedera helix in rats

In Hedera helix hederacoside C, hederacoside D, and ɑ-hederin are three major bioactive saponins and play pivotal roles in the overall biological activity. In this study, a specific and sensitive ultra-high performance liquid chromatography with tandem mass spectrometry method has been developed and validated for the quantification of three major bioactive saponins in rat plasma. Chromatographic separation was performed on a reversed-phase Thermo Hypersil GOLD C18 column (2.1 mm × 50 mm, 1.9 μm) using a gradient mobile phase system of acetonitrile-water containing 0.1% formic acid. The assay was successfully applied to study the pharmacokinetic behavior of the three analytes in rats after oral and intravenous administration of a mixture of saponins (hederacoside C, hederacoside D, and ɑ-hederin). Further research was performed to compare the pharmacokinetic behavior of the three analytes after the oral administration of a mixture of saponins and an extract of saponins from Hedera helix, and results showed that double peaks were evident on concentration-time profile for each of the three saponins. The difference in the pharmacokinetic characteristics of three saponins between a mixture of saponins and an extract of saponins from Hedera helix was found in rat, which would be beneficial for the preclinical research and clinical use of Hedera helix.