MAX-DOAS Measurements of Tropospheric NO2 and HCHO Vertical Profiles at the Longfengshan Regional Background Station in Northeastern China.

The vertical profiles of nitrogen dioxide (NO2) and formaldehyde (HCHO) in the troposphere at the Longfengshan (LFS) regional atmospheric background station (127°36' E, 44°44' N, 330.5 m above sea level) from 24 October 2020 to 13 October 2021 were retrieved from solar scattering spectra by multi-axis differential optical absorption spectroscopy (MAX-DOAS). We analyzed the temporal variations of NO2 and HCHO as well as the sensitivity of ozone (O3) production to the concentration ratio of HCHO to NO2. The largest NO2 volume mixing ratios (VMRs) occur in the near-surface layer for each month, with high values concentrated in the morning and evening. HCHO has an elevated layer around the altitude of 1.4 km consistently. The means ± standard deviations of vertical column densities (VCDs) and near-surface VMRs were 4.69 ± 3.72 ×1015 molecule·cm-2 and 1.22 ± 1.09 ppb for NO2, and they were 1.19 ± 8.35 × 1016 molecule·cm-2 and 2.41 ± 3.26 ppb for HCHO. The VCDs and near-surface VMRs for NO2 were high in the cold months and low in the warm months, while HCHO presented the opposite. The larger near-surface NO2 VMRs appeared in the condition associated with lower temperature and higher humidity, but this relationship was not found between HCHO and temperature. We also found the O3 production at the Longfengshan station was mainly in the NOx-limited regime. This is the first study presenting the vertical distributions of NO2 and HCHO in the regional background atmosphere of northeastern China, which are significant to enhancing the understanding of background atmospheric chemistry and regional ozone pollution processes.

Identification of intestinal metabolic activation of loganin generated dialdehyde reactive intermediates improves intestinal bile salt hydrolase activities.

Loganin is an iridoid with potent pharmacological effects. Loganin contains a hemiacetal structure and can convert to dialdehyde intermediates after deglycosylation. We hypothesized that the metabolites of loganin with hemiacetal can generate reactive dialdehyde intermediates. This study aims to characterize the metabolic profiling of loganin and especially for the unstable dialdehyde intermediates by using ultra-performance liquid chromatograph-quadrupole orbitrap mass spectrometry. In this study, a total of 26 stable metabolites were identified in loganin-treated rats. Loganin underwent different metabolism in the intestine and liver, which was confirmed mainly by the metabolites in the hepatic portal vein. In the intestine, the major metabolic pathways were ester hydrolysis and deglycosylation, followed by methylation and dehydrogenation. The hepatic metabolism pathways were hydrogenation, hydroxylation, glucuronidation, and sulfonation. The circulating metabolites with high abundance were mainly derived from intestinal metabolism. Importantly, 11 unstable dialdehyde intermediates of loganin were identified and described for the first time. The dialdehyde intermediates were identified by their dihydropyridine conjugates with amino acids. The dialdehyde intermediates were mainly produced in the intestine. The dialdehyde intermediates enable covalent modification of intestinal proteins. Loganin can up-regulate the activity of intestinal bile salt hydrolase (BSH), catalyzing bile acid metabolism. The level of protein adducts was positively associated with BSH activity, indicating dialdehyde intermediates played a key role in the up-regulation of BSH activities. In conclusion, this study not only demonstrates the characteristic metabolic fate of loganin but also facilitates the understanding of the pharmacologic effects of dialdehyde intermediates.

Simultaneous determination of six components of Danzhi Xiaoyao Pill in beagle plasma by HPLC-MS/MS and a study of pharmacokinetic of paeoniflorin and geniposide after single-dose administration.

This study was to develop a reliable and simple high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to detect paeoniflorin, geniposide, saikosaponin b2, liquiritin, paeonol and atractylenolide Ⅲ in beagle plasma and to study pharmacokinetic of paeoniflorin and geniposide after single-dose administration of Danzhi Xiaoyao Pill (DZXY). Chromatographic separation was performed using an Agilent C18 column, and multiple reaction monitoring (MRM) mode was used. A gradient elution procedure was used with solvent A (acetonitrile) and solvent B (0.1 % formic acid-water) as mobile phases. The elution procedure was as follows: 85 % B-30 % B (0-7 min) and 30 % B-30 % B (7.1-8 min). The flow rate was 0.3 mL/min. The column temperature was 40 ℃, and the injection volume was 10 µL. The main analytical parameters of paeoniflorin, geniposide, saikosaponin b2, liquiritin, paeonol and atractylenolide Ⅲ were m/z 525→449, m/z 433→224, m/z 780→617, m/z 417→254, m/z 167→43 and m/z 249→231, respectively. Ethyl acetate was used to extract the analytes in the plasma. Standard calibration curves of six analytes showed satisfactory linearity (r2≥0.99 2) within the determined ranges. The lower limits of quantification were 0.5 ng/mL for paeoniflorin and liquiritin, 2.5 ng/mL for geniposide and saikosaponin b2 and 1.0 ng/mL for atractylenolide Ⅲ and paeonol, respectively. The intra-day and inter-day precision (RSD %) were all below 6.94 %, and the intra-day and inter-day accuracy (RE %) were within ± 6.10 %. The recovery and ME of six analytes were 85.99 %-98.10 % and 95.78%-108.06%, respectively. Additionally, the method we established in this experiment can be successfully used to study the pharmacokinetics of paeoniflorin and geniposide in beagle plasma.

Re-evaluating the distribution and variation characteristics of haze in China using different distinguishing methods during recent years.

Haze is identified via different methods using hourly visibility, relative humidity (RH) and PM2.5 mass concentration observations collected from 2013 to 2018 at 502 stations in China. An inter-comparison of a new haze identification method (MGB) and other currently used methods (M80 and M90) is performed in this research. Compared with other methods, the MGB method has an advantage in the expression of fine particle pollution characteristics, especially in high humidity areas. The mean value of the correlation coefficient of the daily mean PM2.5 and daily haze hour obtained by MGB in China is 0.69 which is higher than the correlation coefficients of the daily mean PM2.5 and haze hour identified by the other two methods. Compared with M80, the haze identified by MGB and M90 is less influenced by daily or monthly variations of RH. Approximately 75% of haze occurs when the RH is exceeds 60% or the PM2.5 mass concentration is below 105 µg/m3 over China, no matter which haze identification method is used. Haze has obvious regional distribution characteristics and is relatively higher in Beijing-Tianjin-Hebei and its surrounding areas, and the middle and lower reaches of the Yangtze River. The 6-year mean annual total haze identified by the MGB method is 1167 h for mainland China. Compared with MGB, M80 underestimates the haze hour by -34%, and M90 produces a smaller positive overestimation by 18%. The annual total haze hour of China and its three major economic regions shows significant decreasing trends regardless of the identification method used. Daily variation of haze is obtained in this research via automatic visibility measurement. The daily cycles of haze hour identified by MGB and M90 are similar, whereas that identified by M80 behaves differently affected by daily variation of RH. Haze hour is high in winter and low in summer.