The Pharmacokinetics in Mice and Cell Uptake of Thymus Immunosuppressive Pentapeptide Using LC-MS/MS Analysis.

Thymus immunosuppressive pentapeptide (TIPP) is a novel anti-inflammatory peptide with high efficacy and low toxicity. This study aims to establish a selective LC-MS/MS method for analyzing the analyte TIPP in biological samples, laying the foundation for further PK and PD studies of TIPP. Protein precipitation was conducted in acetonitrile supplemented with 2% formic acid and 25 mg/mL dithiothreitol as a stabilizer, which was followed by backwashing the organic phase using dichloromethane. The chromatographic separation of TIPP was achieved on a C18 column with a gradient elution method. During positive electrospray ionization, TIPP was analyzed via multiple-reaction monitoring. The linear relationships between the concentration of TIPP and peak area in murine plasma cell lysates, supernatants, and the final cell rinse PBS were established within the ranges of 20−5000 ng/mL, 1−200 ng/mL, 10−200 µg/mL, and 0.1−20 ng/mL, respectively (r2 > 0.99). Validated according to U.S. FDA guidelines, the proposed method was proved to be acceptable. Such a method had been successfully applied to investigate the pharmacokinetics of TIPP in mice via subcutaneous injection. The plasma half-life in mice was 5.987 ± 1.824 min, suggesting that TIPP is swiftly eliminated in vivo. The amount of TIPP uptake by RBL-2H3 cells was determined using this method, which was also visually verified by confocal. Furthermore, the effective intracellular concentration of TIPP was deduced by comparing the intracellular concentration of TIPP and degrees of inflammation, enlightening further investigation on the intracellular target and mechanism of TIPP.

A developed HPLC-MS/MS method to quantitate 5 steriod hormones in clinical human serum by using PBS as the surrogate matrix.

Steroid hormones play an essential role in regulating physiological and reproductive development throughout the lifetime of an individual. One of the difficulties in determining endogenous substances is the lack of a blank matrix. Especially when the level of analytes is lower than the level in the so-called blank matrix. In the present study, an optimized HPLC-MS/MS method was developed and validated to quantify androstenedione (ASD), testosterone (Ts), dehydroepiandrosterone (DHEA), 5α-dihydrotestosterone (DHT), and progesterone (P) in serum samples from healthy people using PBS (pH = 7.4) as the blank surrogate matrix. Simultaneously, the method investigated the characteristics of NaCl, bull serum albumin, pure water as surrogate matrices for the analysis of steroid hormones. The data showed that the matrix effects of ASD, Ts, DHEA, DHT, and P in the same groups were not significantly different between PBS and twice charcoal-stripped serum (CS2S) as a blank surrogate matrix. Furthermore, the LLOQ using PBS as the blank matrix was up to 0.005 ng/mL for ASD, Ts, and P and 0.05 ng/mL for DHEA and DHT. The reference ranges of concentration (CPBS) of 5 steroid hormones were provided. Compared to the concentration with CS2S (CCSS) as the blank surrogate matrix, the relative biases (RBs) of Ts, DHT, P, and DHEA were finally stabilized at approximately -0.7%, -15%, -1.2%, and 9.2%, respectively. The results suggest that, in the cases of special required, the developed HPLC-MS/MS method can be used to determine the absolute concentration of 5 hormones in biological samples with PBS as the blank surrogate matrix.

Development of a novel tandem mass spectrometry method for the quantification of eszopiclone without interference from 2-amino-5-chloropyridine and application in a pharmacokinetic study of rat.

Eszopiclone (E-ZOP), a strictly controlled psychoactive drug, must be accurately quantified in biological matrices. However, because of its rapid degradation and transformation into 2-amino-5-chloropyridine (ACP) during specimen preparation, the concentration of E-ZOP in biological matrices is likely underestimated. In this study, a sensitive and simple high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the accurate determination of the initial concentration of E-ZOP in rat plasma was developed and validated. ACP was monitored simultaneously throughout the method validation process to ensure that it was not produced via E-ZOP hydrolysis. E-ZOP and structurally similar metabolites were stabilized in rat plasma by controlling the pH at 4.2 using a modified phosphate buffer solution (PBS) with acetic acid. Using this method, E-ZOP, ACP and the internal standard (IS), venlafaxine, were extracted from rat plasma via a simple protein precipitation and separated on a C18 column using methanol, 5 mM ammonium acetate, and 0.1 % acetic acid as the isocratic mobile phase. The validated method covered a working range from 0.1-50 ng/mL for E-ZOP, and the lower limit of detection (LLOD) for ACP was 0.2 ng/mL. In conclusion, an accurate, sensitive, and simple HPLC-MS/MS method for E-ZOP quantification was developed and successfully applied to a preclinical pharmacokinetics (PK) study in rats. The toxic product APC was effectively monitored. The HPLC-MS/MS method is a stable and sensitive quantitative method for the determination of E-ZOP in biological matrices.

Determination of the in vitro metabolic stability and metabolites of the anticancer derivative riccardin D-N in human and mouse hepatic S9 fractions using HPLC-Q-LIT-MS.

Riccardin D-N (RD-N) is an aminomethylated derivative of the macrocyclic bisbibenzyl compound riccardin D (RD), which has shown stronger activity against cancer cells than RD. However, there has been no research on the metabolism of RD-N. The present study aimed to characterize the in vitro metabolism and metabolic stability of RD-N after incubation with mouse and human hepatic S9 fractions using high performance liquid chromatography-hybrid triple quadrupole/linear ion trap mass spectrometry (HPLC-Q-LIT-MS). Multiple ion monitoring (MIM) and multiple reaction monitoring (MRM)-information dependent acquisition-enhanced product ion (MIM/MRM-IDA-EPI) scans were used to identify the metabolites formed. MRM scans were also used to quantify the changes in the amount of RD-N and to semi-quantify the main metabolites. Twenty-eight metabolic products were detected and 25 structures were predicted. Hydroxylation, dehydrogenation, glucuronidation, and methylation were proposed to be the principle metabolic pathways in the in vitro incubation with human and mouse hepatic S9 fractions. There were differences in the number and abundance of RD-N metabolites between the human and mouse hepatic S9 fractions. RD-N was shown to have good metabolic stability. After 2 h of incubation, 44% of the original RD-N remained in the human hepatic S9 fraction compared with 22% in the mouse. The major metabolites of RD-N, M4, M8, M20 and M21, were monitored semi-quantitatively using the typical transitions. Finally, HPLC-Q-LIT-MS was used for the identification and quantitation of the metabolites of R D-N, which is a simple and efficient method to rapidly screen potential drug candidates.