A UHPLC-QTOF-MS/MS method with a superimposed multiple product ion strategy and esterase inhibitor improved sensitivity for the determination of xylocarpin H in rat plasma.

Xylocarpin H is a natural limonoid that has the potential to be a viable therapeutic candidate whether used alone or in combination with other medications. However, the pharmacokinetic properties of xylocarpin H are still not well understood and require further investigation. Sensitive analysis of xylocarpin H using liquid chromatography tandem triple-quadrupole mass spectrometry is challenging due to its structural feature. In the present research, a sensitive UHPLC-QTOF-MS/MS method was developed and validated to determine xylocarpin H in rat plasma. After simple methanol protein precipitation pretreatment with 50 mM esterase inhibitor bis(4-nitrophenyl)-phosphate (BNPP), xylocarpin H and Schisandrin (internal standard) were separated on a Synergi 4 u fusion-RP C18 column (50 mm × 3.0 mm, 4 µm) using isocratic elution with a mobile phase consisting of formic acid (0.1%) and acetonitrile, which were detected only within 3 min. The QTOF-MS/MS detection, which is a high-resolution mode, can accurately quantify analytes (ppm<5). The peak area of xylocarpin H was determined by adding the single peak areas of m/z 483.2013, m/z 465.1930 and m/z 345.1333 as the superimposed multiple product ions (SMPI) mode for data processing with optimized the high-resolution extraction widths of fragment ions at ± 0.05 Da. The S/N of the SMPI mode was found to be approximately two to seven times greater than the independent product ion mode. The linearity, precision, accuracy, and stability were completely validated for the method. Finally, the validated method was employed for the pharmacokinetic study of xylocarpin H in rats. The study indicated that the optimized high-resolution extraction widths of fragment ions and SMPI mode for data processing significantly improve the quantitative sensitivity of QTOF-MS/MS. In addition, esterase inhibitor BNPP was added in the process of sample treatment to inhibit the degradation of xylocarpin H in rat blood, which further improved the sensitivity of the quantitative method.

Repeated 3,3-Dimethyl-1-butanol exposure alters social dominance in adult mice.

The influence of gut microbiota on brain function and brain disorders has been attracted more and more attention. Trimethylamine N-oxide (TMAO), an indirect metabolite of gut microbiota, has been linked to aging, cognitive impairment, and other brain disorders. However, the relationship between TMAO and social behaviors are still poorly understood. Adult male mice were exposed to drinking water containing 3,3- Dimethyl-1-butanol (DMB), an indirect inhibitors of TMAO, for 21 continuous days followed by a series of behavioral tests to detect the effect of DMB exposure on social behaviors, mainly including social dominance test (SDT), bedding preference test (BP), sexual preference test (SP), social interaction test (SI), open field test (OFT), tail suspension test (TST), forced swim test (FST), novelty suppressed feeding test (NSF), and novel object recognition (NOR) task. In the SDT, compared with the control group, the mice treated with DMB (both 0.2% and 1.0%), both high-ranked and low-ranked mice, showed a reduction in the number of victories. There is no statistical difference on sexual preference, anxiety, depression-like behavior phenotype, and memory formation. In conclusion, the present findings provide direct evidence, for the first time, that repeated DMB exposure produces significant effects on social dominance of adult mice, without any effects on sexual preference, anxiety, depression-like behavior phenotype or memory formation, highlighting the regulatory effects of gut-brain interaction on social behaviors.

Long-lasting effects of postweaning sodium butyrate exposure on social behaviors in adult mice.

BACKGROUND: The function of gut microbiota as its role in normal physiology and involvement in brain function has gained a great deal of attention. The potential long-lasting effects of postweaning sodium butyrate (SB) exposure on social behaviors are still unknown; however it acts as one of the metabolites of gut microbiota. METHODS: Male mice (24-day old) were exposed to SB through drinking water for 21 continuous days. A series of behavioral tests, mainly including bedding preference test (BP), sexual preference test (SP), social interaction test (SI), tube dominance test (SDT), forced swimming test (FST), open field test (OFT), novel object recognition task (NOR) were conducted at different time after 21-d SB exposure. Serum Trimethylamine oxide (TMAO) levels were investigated to gain insight into a potential mechanism. RESULTS: Behavioral results indicated that postweaning SB exposure significantly decreased the social dominance status of low-ranked mice and decreased the sexual preference without affecting social interaction. SB exposure also exerted transient anxiolytic-like effects, while having induced a long-lasting depression-like effect without effects on memory formation. Postweaning SB exposure increased serum TMAO levels in mice, especially in lower-ranked mice, but decreased in higher-ranked mice. LIMITATIONS: Lack of understanding of the underlying mechanism. CONCLUSIONS: These findings provide direct evidence, for the first time, that postweaning SB exposure produces long-term effects on social behaviors in adult mice, mainly referring to sexual orientation, social dominance, and depression-like behaviors, which may be related to the serum TMAO levels, highlighting the long-lasting potential effects of gut-brain interaction on social behaviors.