Harnessing peak transmission around symptom onset for non-pharmaceutical intervention and containment of the COVID-19 pandemic.

Within a short period of time, COVID-19 grew into a world-wide pandemic. Transmission by pre-symptomatic and asymptomatic viral carriers rendered intervention and containment of the disease extremely challenging. Based on reported infection case studies, we construct an epidemiological model that focuses on transmission around the symptom onset. The model is calibrated against incubation period and pairwise transmission statistics during the initial outbreaks of the pandemic outside Wuhan with minimal non-pharmaceutical interventions. Mathematical treatment of the model yields explicit expressions for the size of latent and pre-symptomatic subpopulations during the exponential growth phase, with the local epidemic growth rate as input. We then explore reduction of the basic reproduction number R0 through specific transmission control measures such as contact tracing, testing, social distancing, wearing masks and sheltering in place. When these measures are implemented in combination, their effects on R0 multiply. We also compare our model behaviour to the first wave of the COVID-19 spreading in various affected regions and highlight generic and less generic features of the pandemic development.

[Identification and analysis of absorbed components in rat plasma after oral administration of active fraction of Corydalis yanhusuo by LC-MS/MS].

To analyze and identify the constituents in rat plasma after oral administration of the active fraction of Corydalis yanhusuo, a LC-MS/MS method was established. The constituents absorbed into blood, their original crude drugs and their metabolites were identified either by comparing the retention time and mass spectrometry data with that of reference compounds or by mass spectrometry analysis and retrieving the reference literatures. Nine species are the original form in Corydalis yanhusuo, moreover, some metabolites in blood identified as glucuronide were found. The constituents absorbed into blood and the possible metabolites which demonstrate to originate from the active fraction of Corydalis yanhusuo are responsible for the observed efficacy. Its serum pharmacochemistry should be subjected to complete investigation so as to illuminate the pharmacology and active mechanism of the active fraction of Corydalis yanhusuo.

[Analysis of chemical constituents of anti-myocardial ischemia fraction of Corydalis yanhusuo].

OBJECTIVE: To establish the HPLC fingerprint of anti-myocardial ischemia fraction of Corydalis yanhusuo, and to investigate its chemical constituents by LC-MS-MS. METHOD: The separation was performed at 30 degrees C on a Dikma Diamonsil C18 column (4.6 mm x 250 mm, 5 microm) by isocratic elution with acetonitrile-water (23:77) (containing 0.8% acetic acid and 0.2% triethylamine) as the mobile phase at a flow rate of 1.0 mL x min(-1), with UV detection at 335 nm. RESULT: A satisfactory fingerprint was obtained by HPLC method, 12 common peaks were selected as the fingerprint peaks, and 8 among them were identified according to the chromatographic behavior and mass spectroscopic data by comparison with those of authentic standard. CONCLUSION: This method is simple, sensitive and reliable, can be used to investigate the chemical constituents of anti-myocardial ischemia fraction of C. yanhusuo and control the quality.

[Studies on chemical constituents in the anti-myocardial ischemia effective fraction of Corydalis yanhusuo].

OBJECTIVE: To study the chemical constituents in the anti-myocardial ischemia effective fraction of Corydalis yanhusuo. METHODS: Compounds were isolated and purified by a macroporous resin, Sephadex LH-20, ODS column chromatography, and prepared TLC. Their structures were identified by spectral analysis and chemical evidence. RESULTS: Nine compounds, tetrahydrocolumbamine (1), noroxyhydrastinine (2), corunine (3), dehydrocorydaline (4), dehydrocorybulbine (5), columbamine (6), coptisine (7), berberine (8), palmatine (9) were isolated and identified from the effective fraction of Corydalis yanhusuo. CONCLUSION: Compounds 2, 3 and 5 were isolated from this plant for the first time.

HPLC-MS analysis of ethanol extract of Corydalis yanhusuo and simultaneous determination of eight protoberberine quaternary alkaloids by HPLC-DAD.

An accurate and simple analysis method by high-performance liquid chromatography (HPLC)-electrospray tandem mass spectrometry (ESI-MS-MS) for the ethanol extract of Corydalis yanhusuo was established in this study. In this method, a C(18) column was used, and the mobile phase was water (0.2% acetic acid, 0.1% triethylamine, v/v)-acetonitrile (24:76, v/v). Under the optimal analysis conditions established in this study, eight protoberberine quaternary alkaloids in the ethanol extract of Corydalis yanhusuo were well separated and identified, respectively. Eight regression equations showed a good linear relationship between the peak area of each marker and concentration (r = 0.9990-0.9995). The various other aspects of analysis (i.e., peak purity, precision, recovery, and repeatability) were also validated. For the eight components, the recoveries were found to be 98.9%, 99.2%, 105.0%, 97.7%, 101.4%, 98.6%, 98.5%, and 98.7%, respectively. The limits of detection were 14.6, 42.5, 22.4, 17.9, 25.4, 10.0, 18.7, 3.9 ng/mL, respectively, and the limits of quantitation were 48.6, 141.7, 74.6, 59.6, 84.8, 33.2, 62.3, and 12.9 ng/mL, respectively. The developed method is useful for the simultaneous determination of these alkaloids in a large number of ethanol extracts of Corydalis yanhusuo.

Two new protoberberine quaternary alkaloids from Corydalis yanhusuo.

Two new protoberberine quaternary alkaloids, 13-methyl-palmatrubine (1) and 13-methyl-dehydrocorydalmine (2), were isolated from the tubers of Corydalis yanhusuo W.T. Wang. 1 was isolated as a natural product for the first time, and 2 a new compound. Their structures were elucidated on the basis of spectroscopic evidence, especially 1D- and 2D-NMR experiments.