Perspectives of Positively Charged Nanocrystals of Tedizolid Phosphate as a Topical Ocular Application in Rabbits

The aim of this study was the successful utilization of the positively charged nanocrystals (NCs) of Tedizolid Phosphate (TZP) (0.1% w/v) for topical ocular applications. TZP belongs to the 1, 3-oxazolidine-2-one class of antibiotics and has therapeutic potential for the treatment of many drug-resistant bacterial infections, including eye infections caused by MRSA, penicillin-resistant Streptococcus pneumonia and vancomycin-resistant Enterococcus faecium. However, its therapeutic usage is restricted due to its poor aqueous solubility and limited ocular availability. It is a prodrug and gets converted to Tedizolid (TDZ) by phosphatases in vivo. The sterilized NC₁ was subjected to antimicrobial testing on Gram-positive bacteria. Ocular irritation and pharmacokinetics were performed in rabbits. Around a 1.29 to 1.53-fold increase in antibacterial activity was noted for NC₁ against the B. subtilis, S. pneumonia, S. aureus and MRSA (SA-6538) as compared to the TZP-pure. The NC₁-AqS was “practically non-irritating” to rabbit eyes. There was around a 1.67- and 1.43 fold increase in t_1/2 (h) and C_max (ngmL⁻¹) while there were 1.96-, 1.91-, 2.69- and 1.41-times increases in AUC_0–24h,AUC_0–∞,AUMC_0–∞ and MRT_0–∞, respectively, which were found by NC₁ as compared to TZP-AqS in the ocular pharmacokinetic study. The clearance of TDZ was faster (11.43 mLh⁻¹) from TZP-AqS as compared to NC₁ (5.88 mLh⁻¹). Relatively, an extended half-life (t_1/2; 4.45 h) of TDZ and the prolonged ocular retention (MRT_0–∞; 7.13 h) of NC₁ was found, while a shorter half-life (t_1/2; 2.66 h) of TDZ and MRT_0–∞(t_1/2; 5.05 h)was noted for TZP-AqS, respectively. Cationic TZP-NC₁ could offer increased transcorneal permeation, which could mimic the improved ocular bioavailability of the drug in vivo. Conclusively, NC₁ of TZP was identified as a promising substitute for the ocular delivery of TZP, with better performance as compared to its conventional AqS.     

Physiology-Based Pharmacokinetic Study on 18β-Glycyrrhetic Acid Mono-Glucuronide (GAMG) Prior to Glycyrrhizin in Rats

To understand that 18β-Glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG) showed better pharmacological activity and drug-like properties than 18β-Glycyrrhizin (GL); a rapid and sensitive HPLC-MS/MS method was established for the simultaneous determination of GAMG and its metabolite 18β-Glycyrrhetinic acid (GA) in rat plasma and tissues after oral administration of GAMG or GL. This analytical method was validated by linearity, LLOQ, specificity, recovery rate, matrix effect, etc. After oral administration, GAMG exhibited excellent C_max (2377.57 ng/mL), T_max (5 min) and AUC_0-T (6625.54 mg/L*h), which was much higher than the C_max (346.03 ng/mL), T_max (2.00 h) and AUC_0-T (459.32 mg/L*h) of GL. Moreover, GAMG had wider and higher tissue distribution in the kidney, spleen, live, lung, brain, etc. These results indicated that oral GAMG can be rapidly and efficiently absorbed and be widely distributed in tissues to exert stronger and multiple pharmacological activities. This provided a physiological basis for guiding the pharmacodynamic study and clinical applications of GAMG.     

A new HPLC–MS/MS method for the simultaneous quantification of SGLT2 inhibitors and metformin in plasma and its application to a pharmacokinetic study in healthy volunteers

Monitoring the plasma concentrations of metformin and sodium‐glucose cotransporter‐2 inhibitors (canagliflozin, dapagliflozin and empagliflozin) is essential for pharmacokinetic and bioequivalence studies and therapeutic monitoring. The present work therefore aimed to develop and validate a high‐performance liquid chromatography coupled to tandem mass spectrometry (HPLC–MS/MS) method for the simultaneous quantification of these drugs in human plasma. The analyses were performed using an Agilent 1200 HPLC system coupled to an Applied Biosystems API 3200 triple quadrupole MS/MS with electrospray ionization in positive ion mode. After one‐step protein precipitation of plasma with acetonitrile containing 0.1% formic acid, chromatographic separation was achieved on an Xbridge C₁₈ column, with a mobile phase consisting of a gradient of water and acetonitrile, both containing 1 mm ammonium formate and 0.1% formic acid. Quantification was performed in multiple reaction monitoring mode using m/z 130.1 → 71.1 for metformin, m/z 462.0 → 191.2 for canagliflozin, m/z 426.1 → 167.1 for dapagliflozin and m/z 468.0 → 354.9 for empagliflozin. The proposed method was validated and demonstrated to be adequate for the quantification of metformin, canagliflozin, dapagliflozin and empagliflozin for clinical monitoring, pharmacokinetics and bioequivalence studies.     

Toxicity profiling and prioritization of plant-derived antimalarial agents

ABSTRACT

Human malaria is the most widespread mosquito-borne life-threatening disease worldwide. In the absence of effective vaccines, prevention and treatment of malaria only depend on prophylaxis and drug-based therapy either in monotherapy or in combination. Unfortunately, the number of available antimalarial drugs presenting different mechanisms of action is rather limited. In addition, the appearance of drug-resistance in the parasite strains impacts the efficacy of the treatments. As a result, there is a crucial need to find new drugs to circumvent resistance problems. In the quest to identify new antimalarial agents a huge number of plant-derived compounds (PDCs) have been investigated. Surprisingly in the in silico PDC screening programs, toxicity filters are either never used or so simple that their interest is limited. In this context, the goal of this study was to show how to take advantage of validated toxicity QSAR models for refining the selection of PDCs. From an original data set of 507 PDCs collected from the literature, the use of toxicity filters for endocrine disruption, developmental toxicity, and hepatotoxicity in conjunction with classical pharmacokinetic filters allowed us to obtain a list of 31 compounds of potential interest. The pros and cons of such a strategy have been discussed.     

Simultaneous quantification of ligustilide,dl‐3‐n‐butylphthalide and senkyunolide A in rat plasma by GC–MS and its application to comparative pharmacokinetic studies of Rhizoma Chuanxiong extract alone and Baizhi Chuanxiong Decoction

The herb couple has special clinical significance in reducing the toxicity and increasing the efficacy of drugs. The combination of Radix Angelicae Dahuricae (Baizhi, BZ) and Rhizoma Chuanxiong (ChuanXiong, CX) is a traditional herb couple. The combination performs better than the CX extract alone in the treatment of migraine and has been used for thousands of years. However, the specific compatibility mechanisms are still unclear. Ligustilide, dl ‐3‐n‐butylphthalide and senkyunolide A are the major active ingredients in CX and BZ–CX decoction. However, a comprehensive study of the pharmacokinetics of CX has not been carried out. A gas chromatography–mass spectroscopy (GC–MS) method with high selectivity, sensitivity and accuracy was developed. An SH‐Rxi‐5Sil (30 m × 0.25 mm i.d., and 0.25 μm film thickness) column was employed in the GC separation. Selectivity, linearity, precision, accuracy, recovery, matrix effect and stability were used to validate the current GC–MS method. Using the validated method, this is the first time to study on the comparative pharmacokinetics of ligustilide, dl ‐3‐n‐butylphthalide and senkyunolide A from CX alone and BZ–CX decoction in rat plasma. The pharmacokinetic parameters (C_max, T_max, T_1/2, AUC_0–t, AUC_0–∞ and CLz/F) of all of the detected ingredients showed significant differences between the two groups (P < 0.05). The results are helpful for further investigation of the compatibility mechanism of BZ–CX decoction.     

A reliable LC–MS/MS method for the quantification of five bioactive saponins of crude and processed Bupleurum scorzonerifolium in rat plasma and its application to a pharmacokinetic study

A simple and reliable liquid chromatography–mass spectrometry (LC–MS) method was developed for simultaneous determination of saikosaponin A, saikosaponin B₁, saikosaponin C, saikosaponin D and saikosaponin F in rat plasma using glycyrrhetinic acid as an internal standard (IS). The separation was operated on a Waters BEH C₁₈ column. The mobile phases of gradient elution consisted of acetonitrile (A) and 0.1% aqueous acetic acid (B). The mass spectrometric detection was accomplished in multiple reaction monitoring mode. The five saponins displayed good linearity (r² > 0.9996). The lower limits of quantitation of saikosaponin A, saikosaponin B₁, saikosaponin C, saikosaponin D and saikosaponin F were determined to be 2.9, 2.3, 3.5, 2.9 and 3.1 ng/mL, respectively. Moreover, the intra‐ and inter‐day precisions of the five saponins showed an RSD within 2.96%, whereas the accuracy (RE) ranged from ?2.28 to 2.78%. Finally, the developed method was fully validated and applied to a comparative pharmacokinetic study of the five bioactive saponins in rats following oral administration of crude and vinegar‐processed Bupleurum scorzonerifolium.     

Metabolic characteristics and pharmacokinetic differences of Qiwei Tongbi oral liquid in rheumatoid arthritis rats

Qiwei Tongbi oral liquid (QWTB), a classical traditional Chinese medicine formula, is widely used to treat arthritis-related diseases in clinical practice. Currently, in vivo metabolic characteristics and pharmacokinetic studies are lacking. This study analyzed the prototype components of QWTB absorbed in the blood and their metabolic transformation process after intragastric administration and compared the differences in pharmacokinetic properties between healthy and rheumatoid arthritis model rats. In sum, 17 prototype components and 21 related metabolites were identified in the plasma and urine of the treated rats. Metabolites were derived from sinomenine and magnoflorine. Through systematic methodology verification, an accurate and stable detection method for sinomenine and magnoflorine in plasma samples was established and applied to pharmacokinetic research of QWTB. At the three dose levels, the AUC_0–∞ (area under the curve) of the two components showed a good positive correlation with the dose (R² > 0.9). Compared with healthy rats, the T_max, t_1/2z, and AUC of sinomenine were markedly increased, and C_max was decreased in rheumatoid arthritis model rats, indicating that the rate of absorption and elimination rate decreased, but the body exposure increased. However, there were no significant differences in the pharmacokinetic parameters of magnoflorine under healthy and pathological conditions. In summary, the main active ingredients of QWTB are sinomenine and magnoflorine, which exhibit linear kinetic characteristics within a set dose range, and the rheumatoid arthritis pathological state is more conducive to the absorption and efficacy of sinomenine. The results of this study demonstrate the rationality of the clinical application of the QWTB.     

Pharmacokinetics and bioavailability study of ginsenoside Rk1 in rat by liquid chromatography/electrospray ionization tandem mass spectrometry

Ginsenoside Rk1 (Rk1) exhibited various potent biological activities. However, its pharmacokinetic profile in vivo remains unclear. In the present study, a simple and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for determination of Rk1 in rat plasma and applied in a pharmacokinetic study. The sample was precipitated with acetonitrile and separated on a Zorbax Eclipse XDB C18 column (50 × 2.1 mm, 1.8 μm). The mobile phase was composed of 0.1% formic acid in water and acetonitrile at a flow rate of 0.4 mL/min. Rk1 and internal standard (ginsenoside Rg3) were quantitatively monitored with precursor‐to‐product ion transitions of m/z 765.4 → 441.5 and m/z 783.5 → 621.4, respectively. The assay was linear over the concentration range of 5–1000 ng/mL (r > 0.99) with the LLOQ of 5 ng/mL. Other parameters including intra‐ and inter‐day precision and accuracy, extraction recovery and matrix effect were within the acceptable limits. The analyte was stable under the tested storage conditions. The validated method has been successfully applied to a pharmacokinetic study of Rk1 in rat plasma after intravenous (5 mg/kg) and oral (25 mg/kg, 50 mg/kg) administration. After oral administration, Rk1 could be detected in blood at 30 min and reached the highest concentration at 4.29~4.57 h. Our results demonstrated that Rk1 showed low clearance, moderate half‐life (3.09–3.40 h) and low bioavailability (2.87–4.23%). The study will provide information for the further application of Rk1.     

Cellular pharmacokinetics and pharmacodynamics mechanisms of ginkgo diterpene lactone and its modulation of P‐glycoprotein expression in human SH‐SY5Y cells

Ginkgo diterpene lactone (GDL) is the raw material for ginkgo diterpene lactone meglumine injection, which is used for treating cerebral ischemia. The aims of this study were to explore the cellular pharmacokinetics of GDL in whole cells and subcellular fractions, and detect cellular pharmacodynamics on the human SH‐SY5Y cells induced by oxygen–glucose deprivation and reoxygenation (OGD/R). Firstly, a simple, sensitive and reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for assessing the amount of ginkgolide A (GA), B (GB) and K (GK) in cellular/subcellular samples. Then, phosphatidylserine and mitochondria membrane potential were assayed to evaluate the extent of apoptosis effect. The study showed that the cellular/subcellular accumulation of GA and GB were increased in a concentration‐dependent manner; the levels of GA and GB in cytosol were the highest among these subcellular organelles. Meanwhile, GDL also attenuated the OGD/R‐induced increases in the percentage of apoptotic and mitochondria membrane potential. In addition, verapamil increased the rate and amount of GA and GB entering cellular/subcellular compartments through inhibition of P‐glycoprotein activity, and promoted the protective effect of GDL. The present study reports the cellular pharmacokinetics profiles of GA and GB in normal and OGD/R‐induced SH‐SY5Y cells in vitro for the first time, which provided valuable information for clinical safety application.     

Rp-HPLC Determination of Quercetin in a Novel D-α-Tocopherol Polyethylene Glycol 1000 Succinate Based SNEDDS Formulation: Pharmacokinetics in Rat Plasma

Despite its proven efficacy in diverse metabolic disorders, quercetin (QU) for clinical use is still limited because of its low bioavailability. D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) is approved as a safe pharmaceutical adjuvant with marked antioxidant and anti-inflammatory activities. In the current study, several QU-loaded self-nanoemulsifying drug delivery systems (SNEDDS) were investigated to improve QU bioavailability. A reversed phase high performance liquid chromatography (RP-HPLC) method was developed, for the first time, as a simple and sensitive technique for pharmacokinetic studies of QU in the presence of TPGS SNEDDS formula in rat plasma. The analyses were performed on a Xterra C₁₈ column (4.6 × 100 mm, 5 µm) and UV detection at 280 nm. The analytes were separated by a gradient system of methanol and phosphate buffer of pH 3. The developed RP-HPLC method showed low limit of detection (LODs) of 7.65 and 22.09 ng/mL and LOQs of 23.19 and 66.96 ng/mL for QU and TPGS, respectively, which allowed their determination in real rat plasma samples. The method was linear over a wide range, (30–10,000) and (100–10,000) ng/mL for QU and TPGS, respectively. The selected SNEDDS formula, containing 50% w/w TPGS, 30% polyethylene glycol 200 (PEG 200), and 20% w/w pumpkin seed oil (PSO), showed a globule size of 320 nm and −28.6 mV zeta potential. Results of the pharmacokinetic studies showed 149.8% improvement in bioavailability of QU in SNEDDS relative to its suspension. The developed HPLC method proved to be simple and sensitive for QU and TPGS simultaneous determination in rat plasma after oral administration of the new SNEDDS formula.