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Background: The high virulence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for coronavirus disease 2019 (COVID-19), has triggered global health and economic concerns. The absence of specific antiviral treatments and the side effects of repurposed drugs present persistent challenges. This study explored a promising antiviral herbal extract against SARS-CoV-2 from selected Thai medicinal plants based on in vitro efficacy and evaluated its antiviral lead compounds by molecular docking. Methods: Twenty-two different ethanolic-aqueous crude extracts (CEs) were rapidly screened for their potential activity against porcine epidemic diarrhea virus (PEDV) as a surrogate using a plaque reduction assay. Extracts achieving ≥ 70% anti-PEDV efficacy proceeded to the anti-SARS-CoV-2 activity test using a 50% tissue culture infectious dose method in Vero E6 cells. Molnupiravir and extract-free media served as positive and negative controls, respectively. Potent CEs underwent water/ethyl acetate fractionation to enhance antiviral efficacy, and the fractions were tested for anti-SARS-CoV-2 performance. The fraction with the highest antiviral potency was identified using liquid chromatography–high-resolution mass spectrometry (LC–HRMS). Molecular docking analyses of these compounds against the main protease (Mpro) of SARS-CoV-2 (6LU7) were performed to identify antiviral lead molecules. The top three hits were further evaluated for their conformational stability in the docked complex using molecular dynamics (MD) simulation. Results: The water fraction of mulberry (Morus alba Linn.) leaf CE (WF-MLCE) exhibited the most potent anti-SARS-CoV-2 efficacy with low cytotoxicity profile (CC50 of ~ 0.7 mg/mL), achieving 99.92% in pre-entry mode and 99.88% in postinfection treatment mode at 0.25 mg/mL. Flavonoids and conjugates were the predominant compounds identified in WF-MLCE. Molecular docking scores of several flavonoids against SARS-CoV-2 Mpro demonstrated their superior antiviral potency compared to molnupiravir. Remarkably, myricetin-3-O-β-D-galactopyranoside, maragrol B, and quercetin 3-O-robinobioside exhibited binding energies of ~ − 9 kcal/mol. The stability of each ligand–protein complex of these compounds with the Mpro system showed stability during MD simulation. These three molecules were pronounced as antiviral leads of WF-MLCE. Given the low cytotoxicity and high antiviral potency of WF-MLCE, it holds promise as a candidate for future therapeutic development for COVID-19 treatment, especially considering its economic and pharmacological advantages. [ABSTRACT FROM AUTHOR]

A method is described that permits automated online enrichment of injected compounds in multidimensional gas chromatography by using a microfluidic heart-cut (H-C) device to direct target compounds into a cryogenically cooled internal trap (cryotrap, CT). By performing multiple injections of a sample, selected compounds or regions of a primary column separation can be collected in the CT. Remobilizing the trapped species allows elution and further resolution on the second column. Using a well-balanced H-C device, compounds can be fully excluded from the collection step or quantitatively transferred to the CT. Peak areas of the remobilized compound correlate well with the number of sample injections. Trapping on various column phases shows the method is suited to quantitative trapping of alkanes of mass greater than about dodecane and fatty acid methyl esters greater than the C8 homologue. Caffeine and menthol standards of concentration 100 μg mL-1 gave peak area correlation coefficients for 1-10 and 1-50 replicate split injections of 1 μL volume of 0.999 and 0.996, respectively. Peak height correlations were less favorable as a result of peak broadening on the second column, presumably due to overloading at greater collected mass. The method was applied to 0.2% solutions of peppermint oil (menthol; a major component; 44%) and 1.0% lavender oil (α-terpineol and neryl acetate; minor components of 1.05 and 0.42% abundance). The minor components gave good area and height correlations, and good recovery around 90% was observed for menthol compounds recovered from 15 accumulations. Response amplification was further demonstrated for menthol from mint oil headspace sampling using solid phase microextraction. This approach should be a valuable adjunct for improved detection specificity, for detectors of low sensitivity, and when prior sample concentration provides insufficient response of selected target analytes. [ABSTRACT FROM AUTHOR]