[Effects of tetramethylpyrazine on pharmacokinetics in plasma and brain dialysate and neuropathic pain in rat model of spared sciatic nerve injury].

This study aims to explore the effects of tetramethylpyrazine(TMP) on pharmacokinetics in plasma and brain dialysate and neuropathic pain in the rat model of partial sciatic nerve injury(SNI), and to investigate the correlation between the analgesic effect of TMP and its concentrations in the plasma and brain dialysate. Male SD rats were randomized into Sham, SNI, and SNI+TMP groups. Mechanical stimulation with von frey filaments and cold spray method were employed to evaluate the mechanical sensitivity and cold sensitivity of rats. Another two groups, Sham+TMP and SNI+TMP, were used to intubate the common jugular vein and implant microdialysis probes into the anterior cingulate gyrus(ACC), respectively.After intraperitoneal injection of TMP at a dose of 80 mg·kg~(-1), automatic blood collection and intracerebral microdialysis(perfusion rate of 1 µL·min~(-1)) systems were used to collect the blood and brain dialysate for 24 h. HSS T3 C_(18) reversed-phase chromatographic column(2.1 mm×50 mm, 2.5 µm) was used for liquid chromatographic separation. Gradient elution was carried out with the mobile phase of methanol-water(containing 0.005% formic acid) at a flow rate of 0.25 mL·min~(-1). Electrospray ion source was used for mass spectrometry, and the scanning mode was multi-reaction monitoring under the positive ion mode. The ion pairs for quantitative analysis were TMP m/z 137/122 and aspirin m/z 179/137, respectively. DAS 2.11 was used to calculate the pharmacokinetic parameters. The optimal time of TMP to exert the analgesia effect and inhibit cold pain sensitivity was 60 min after treatment. The TMP in the plasma and brain dialysate of SNI rats showed the T_(max) of 15 min and 30 min, the C_(max) of(2 866.43±135.39) and(1 462.14±197.38) µg·L~(-1), the AUC_(0-t) of(241 463.30±28 070.31) and(213 115.62±32 570.07) µg·min·L~(-1), the MRT_(0-t) of(353.13±47.73) and(172.16±12.72) min, and the CL_Z of 0.73 and 0.36 L·min·kg~(-1), respectively. The analgesic effect of TMP had a significant correlation with the blood drug concentration in the ACC, which indicated that this method was suitable for the detection of TMP in rat plasma and brain dialysate. The method is accurate, reliable, and sensitive and can realize the important value of the application of correlation analysis theory of "automatic blood collection-microdialysis/PK-PD" in the research on neuropathic pain.

Ethno-medicinal study of Artemisia ordosica Krasch. (traditional Chinese/Mongolian medicine) extracts for the treatment of allergic rhinitis and nasosinusitis.

ETHNOPHARMACOLOGICAL RELEVANCE: Artemisia ordosica Krasch. (AOK) has been used for rheumatic arthritis, cold headache, sore throat, etc. in traditional Chinese/Mongolian medicine and is used for nasosinusitis by local Mongolian "barefoot" doctors. Up to now, their mechanisms are still unclear. AIM: To evaluate the in vivo anti-inflammatory and allergic rhinitis (AR) alleviating effect as well as in vitro antimicrobial activities of AOK extracts to verify its ethno-medicinal claims. MATERIALS AND METHODS: Crude extracts (methanol/95%-ethanol/ethyl acetate) of AOK root/stem/leaf and fractions (petroleum ether/ethyl acetate/n-butanol/aqueous) of AOK root extract were prepared. Xylene-induced ear swelling model in mouse and ovalbumin (OVA)-induced AR model in guinea pig were established. Ear swelling degrees of mice were measured. The numbers of rubbing movement and sneezes of guinea pigs were counted to evaluate the symptoms of AR. The serum levels of histamine, INF-γ, IL-2/4/10, and VCAM-1 were measured by ELISA assay. The histological changes of nasal mucosa were investigated by light microscope after H&E staining. Antimicrobial activities of AOK extracts were also tested. LC-MS/MS analysis was performed to characterize the constituents of active extract and molecular docking was conducted to predict the biological mechanism. RESULTS: In ear-swelling model, extract (100.00 mg/kg) from the ethyl acetate layer of 95% ethanol (100.00 mg/kg) showed better swelling inhibition in mice than positive control (dexamethasone, 191.91 mg/kg). In AR model, extract from the ethyl acetate layer of 95% ethanol significantly alleviated the AR symptoms in guinea pigs, decreased the serum levels of histamine, INF-γ, IL-2/4/10, and VCAM-1, and reduced the infiltration of eosinophil in nasal mucosa. For Staphylococcus aureus, the ethyl acetate extract of AOK stem showed the highest inhibition (MIC=1.25 mg/mL), for Escherichia coli, n-butanol layer of 95% ethanol extract of AOK root showed the highest inhibition (MIC=15.00 mg/mL), for Candida glabrata, 95%-ethyl acetate extract of AOK leaf showed the best inhibition (MIC=0.064 mg/mL), while ethyl acetate and n-butanol layers showed similar inhibition on MRSA (MIC=7.50 mg/mL). LC-MS/MS characterization showed that dicaffeoylquinic acids account for more than 30% of ethyl acetate layer of AOK extract. Dicaffeoylquinic acids bind with histamine-1 receptor with high affinities and interesting modes. CONCLUSIONS: Extracts from AOK had interesting anti-inflammatory activity in mice, alleviating effect against OVA-induced AR in guinea pigs, and antimicrobial activities in vitro, which support the ethno-medicinal use of it. The main constituents in ethyl acetate layer of AOK root extract are dicaffeoylquinic acids and could bind with histamine-1 receptor well. These findings highlighted the importance of natural product chemistry study of AOK.

ESIMS and NMR studies on the selective deprotection of acetylated glucosides by dibutyltin oxide.

The reaction process for the selective deprotection of acetylated glucosides by dibutyltin oxide in methanol is investigated by using methyl 2,3,4,6-tetra-O-acetyl-α-d-glucopyranoside as a model substrate with ESIMS and NMR techniques. According to the results, it is inferred that at first, dimeric 1,3-dimethoxytetrabutyldistannoxane is formed by the reaction of dibutyltin oxide with methanol, and then the tetraorganodistannoxane reacts with the acetylated glucoside to produce glucoside-organotin complex intermediates. Finally, the complex intermediates are hydrolyzed leading to the free-OH glucoside and organotin acetate derivatives. The reaction is affected by neighboring group participation and steric hindrance, which allow for high selectivities among different acetyl groups in acetylated glucosides.