Bioanalytical assay development and validation for simultaneous quantification of five schisandra lignans in rat primary hepatocytes based on LC-MS/MS: application to a real-time uptake study for Schisandra Lignan Extract

Improved pharmacokinetics of tenofovir ester prodrugs strengthened the inhibition of HBV replication and the rebalance of hepatocellular metabolism in preclinical models

Tenofovir (TFV) ester prodrugs, a class of nucleotide analogs (NAs), are the first-line clinical anti-hepatitis B virus (HBV) drugs with potent antiviral efficacy, low resistance rate and high safety. In this work, three marketed TFV ester drugs, tenofovir disoproxil fumarate (TDF), tenofovir alafenamide fumarate (TAF) and tenofovir amibufenamide fumarate (TMF), were used as probes to investigate the relationships among prodrug structures, pharmacokinetic characteristics, metabolic activations, pharmacological responses and to reveal the key factors of TFV ester prodrug design. The results indicated that TMF and TAF exhibited significantly stronger inhibition of HBV DNA replication than did TDF in HBV-positive HepG2.2.15 cells. The anti-HBV activity of TMF was slightly stronger than TAF after 9 days of treatment (EC₅₀ 7.29 ± 0.71 nM vs. 12.17 ± 0.56 nM). Similar results were observed in the HBV decline period post drug administration to the HBV transgenic mouse model, although these three TFV prodrugs finally achieved the same anti-HBV effect after 42 days treatments. Furthermore, TFV ester prodrugs showed a correcting effect on disordered host hepatic biochemical metabolism, including TCA cycle, glycolysis, pentose phosphate pathway, purine/pyrimidine metabolism, amino acid metabolism, ketone body metabolism and phospholipid metabolism. The callback effects of the three TFV ester prodrugs were ranked as TMF > TAF > TDF. These advantages of TMF were believed to be attributed to its greater bioavailability in preclinical animals (SD rats, C57BL/6 mice and beagle dogs) and better target loading, especially in terms of the higher hepatic level of the pharmacologically active metabolite TFV-DP, which was tightly related to anti-HBV efficacy. Further analysis indicated that stability in intestinal fluid determined the actual amount of TFV prodrug at the absorption site, and hepatic/intestinal stability determined the maintenance amount of prodrug in circulation, both of which influenced the oral bioavailability of TFV prodrugs. In conclusion, our research revealed that improved pharmacokinetics of TFV ester prodrugs (especially intestinal stability) strengthened the inhibition of HBV replication and the rebalance of hepatocellular metabolism, which provides new insights and a basis for the design, modification and evaluation of new TFV prodrugs in the future.

A Comparative Pharmacokinetic Study of Schisandrol B After Oral Administration of Schisandrol B Monomer and Schisandra chinensis Extract

Background:

Schisandra chinensis Turcz. (Baill.) is a perennial deciduous woody vine plant, which is beneficial to all systems of the body.

Objective:

The goals of the present study were to compare the pharmacokinetics of schisandrol B in rats after the oral administration of schisandrol B monomer (10 mg/kg) and S. chinensis extract (equivalent to 10 mg/kg schisandrol B) and to explore interactions among the components in S. chinensis extract.

Methods:

Twelve Sprague-Dawley rats of SPF grade were randomly divided into the monomer and S.chinensis extract groups. Plasma samples were extracted with methyl tert-butyl ether, and chromatographic separation was performed on an Agilent ZORBAX Eclipse XDB-C18 (4.6 × 150 mm, 5 μm) column with the mobile phase consisting of methanol (containing 0.1% formic acid)-water (containing 0.1% formic acid and 5 mmol ammonium acetate). This analysis was achieved by multiple reaction monitoring modes in an electrospray interface.

Results:

The seven lignans had a good linear relationship within the determination range (r>0.9950); the intra- and inter-day precision was <12.08% and accuracy was 88.64%-111.61%. The pharmacokinetic parameters (T1/2, Tmax, MRT0-∞, CL, AUC0-t, and AUC0-∞) of schisandrol B showed significant differences between the two groups (P<0.05).

Conclusion:

The validated method has been successfully applied to the pharmacokinetics of schisandrin, schisandrol B, schisandrin A, schisandrin B, schisandrin C, schisanhenol, and schisantherin A. The pharmacokinetic differences indicate that other components in the extract may increase the absorption of schisandrol B, decrease the rate of elimination, and improve the bioavailability of schisandrol B.

Technologies to improve the sensitivity of existing chromatographic methods used for bioanalytical studies

Chromatographic method has long been recognized as the most widely used separation method in bioanalytical research. However, the relatively low sensitivity of existing chromatographic methods remains a significant challenge, as the requirements for experimental procedures become more demanding. This review discusses the main causes for the low sensitivity of chromatographic methods and aims to introduce different technologies for enhancing their sensitivity in the following aspects: (i) different pretreatment methods for improving clean-up efficiency and recovery; (ii) derivatization step for altering the chromatographic behavior of analytes and enhancing MS ionization efficiency; (iii) optimal LC-MS conditions and appropriate separation mechanism; and (iv) applications of other chromatographic methods, including miniaturized LC, 2D-LC, 2D-GC, and supercritical fluid chromatography. Altogether, this review is devoted to summarizing the recent technologies reported in the literature and providing new strategies for the detection of bioanalytes.

Determination of Schisandrin A and Schisandrin B in Traditional Chinese Medicine Preparation Huganpian Tablet by RP-HPLC

A reverse phase (RP)-HPLC method for separation and determination of Schisandrin A and Schisandrin B was presented, using a C18 Bondclone column, with methanol-water (v/v = 68 : 32) as mobile phase at a flow-rate of 1.00 mL·min^-1, and UV detection at 220 nm. The tested parameters included mobile phase composition and UV detection wavelength. Good linearities were observed within concentration ranges of Schisandrin A 0.008-4.8 mg·L^-1 (r = 0.9996), and Schisandrin B 0.005-3.1 mg·L^-1 (r = 0.9994), respectively. The limit of detection (LOD) (S/N = 3) were 0.005 mg·L^-1 Schisandrin A and 0.002 mg·L^-1 Schisandrin B, respectively. The method was applied to determine the 2 compounds in a traditional Chinese medicine preparation for treatment of hepatic diseases, Huganpian tablet. To eliminate matrix effect, Oasis hydrophilic lipophilic balance (HLB) solid-phase extraction (SPE) was used to purify the ultra-sonicately extracted solution of the drug sample. Combined with the HLB SPE purification procedure, the HPLC method gave satisfactory results for quantitation of Schisandrin A and Schisandrin B in 3 types of Huganpian tablet samples, with spiking recoveries ca. 98% (relative standard deviation (R.S.D.) ≤ 3.5%) (n = 5).