Optimization of Ultrasonic-Assisted Extraction of α-Glucosidase Inhibitors from Dryopteris crassirhizoma Using Artificial Neural Network and Response Surface Methodology.

Dryopteris crassirhizoma Nakai is a plant with significant medicinal properties, such as anticancer, antioxidant, and anti-inflammatory activities, making it an attractive research target. Our study describes the isolation of major metabolites from D. crassirhizoma, and their inhibitory activities on α-glucosidase were evaluated for the first time. The results revealed that nortrisflavaspidic acid ABB (2) is the most potent α-glucosidase inhibitor, with an IC50 of 34.0 ± 0.14 µM. In addition, artificial neural network (ANN) and response surface methodology (RSM) were used in this study to optimize the extraction conditions and evaluate the independent and interactive effects of ultrasonic-assisted extraction parameters. The optimal extraction conditions are extraction time of 103.03 min, sonication power of 342.69 W, and solvent-to-material ratio of 94.00 mL/g. The agreement between the predicted models of ANN and RSM and the experimental values was notably high, with a percentage of 97.51% and 97.15%, respectively, indicating that both models have the potential to be utilized for optimizing the industrial extraction process of active metabolites from D. crassirhizoma. Our results could provide relevant information for producing high-quality extracts from D. crassirhizoma for functional foods, nutraceuticals, and pharmaceutical industries.

A Seroprevalence Study on Residents in a Senior Care Facility with Breakthrough SARS-CoV-2 Omicron Infection.

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) began spreading rapidly in the community in November 2021, becoming the dominant variant in the Republic of Korea in 2022. Although its pathogenesis in healthy individuals was low, the severity and hospitalization rate was higher in the elderly and immunocompromised patients. We aimed to investigate the immunogenicity in acute and convalescent phases of breakthrough infection by Omicron in elderly individuals. Serological data were assessed by electrochemiluminescence immunoassay, enzyme-linked immunosorbent assay, and plaque-reduction neutralization tests. SARS-CoV-2-specific antibody and immunoglobulin G levels in the acute phase were higher in third dose-vaccinated elderly than in first and second dose-vaccinated patients. The neutralization antibody titer was detected only in third dose-vaccinated patients, and the titer was higher for the Delta than the Omicron variant. In the convalescent phase of Omicron infection, the neutralization antibody titer of vaccinated patients was higher for the Delta than the Omicron variant except in unvaccinated individuals. We demonstrated that the cause of the vulnerability to Omicron variant infection in third dose-vaccinated elderly was due to the low neutralization antibody level against Omicron. A fourth dose of vaccination is required in the elderly to reduce hospitalization and mortality caused by the Omicron variant.

Genomic epidemiology of SARS- CoV-2 Omicron variants in the Republic of Korea.

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic since 2019. Variants of concern (VOCs) declared by the World Health Organization require continuous monitoring because of their possible changes in transmissibility, virulence, and antigenicity. The Omicron variant, a VOC, has become the dominant variant worldwide since November 2021. In the Republic of Korea (South Korea), the number of confirmed cases increased rapidly after the detection of Omicron VOC on November 24, 2021. In this study, we estimated the underlying epidemiological processes of Omicron VOC in South Korea using time-scaled phylodynamic analysis. Three distinct phylogenetic subgroups (Kor-O1, Kor-O2, and Kor-O3) were detected in South Korea. The Kor-O1 subgroup circulated in the Daegu region, whereas Kor-O2 and Kor-O3 circulated in Incheon and Jeollanam-do, respectively. The viral population size and case number of the Kor-O1 subgroup increased more rapidly than those of the other subgroups, indicating the rapid spread of the virus. The results indicated the multiple introductions of Omicron sub-lineages into South Korea and their subsequent co-circulation. The evolution and transmission of SARS-CoV-2 should be continuously monitored, and control strategies need to be improved to control the multiple variants.

An outbreak of SARS-CoV-2 reinfection in a long-term care facility in South Korea.

We report a cluster of 12 cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection in a long-term care facility in South Korea. There were two outbreaks of SARS-CoV-2 infection in the facility at the beginning and end of October 2021, respectively. All residents in the facility were screened for SARS-CoV-2 infection using RT-PCR as part of the investigation of the second outbreak. Twelve residents, who had infection confirmed during the first outbreak, were found to be re-positive for RT-PCR test at the second outbreak. 8 Of 12 RT-PCR re-positive cases were confirmed as reinfections based on investigation through the whole genome sequencing, viral culture, and serological analysis, despite of the short interval between the first and second outbreaks (29-33 days) and a history of full vaccination for 7 of the 12 re-positive cases. This study suggests that decreased immunity and underlying health condition in older adults makes them susceptible to reinfection, highlighting the importance of prevention and control measures regardless of vaccination status in long-term care settings.

Genomic evidence of SARS-CoV-2 reinfection in the Republic of Korea.

As the coronavirus disease 2019 (COVID-19) pandemic continues, reinfection is likely to become increasingly common. However, confirming COVID-19 reinfection is difficult because it requires whole-genome sequencing of both infections to identify the degrees of genetic differences. Since the first reported case of reinfection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the Republic of Korea in April 2020, four additional cases were classified as suspected reinfection cases. We performed whole-genome sequencing of viral RNA extracted from swabs obtained at the initial infection and reinfection stages of these four suspected cases. The interval between initial infection and reinfection of all four suspected cases was more than 3 months. All four patients were young (10-29 years), and they displayed mild symptoms or were asymptomatic during the initial infection and reinfection episodes. The analysis of genome sequences combined with the epidemiological results revealed that only two of the four cases were confirmed as reinfection, and both were reinfected with the Epsilon variant. Due to the prolonged COVID-19 pandemic, the possibility of reinfections with SARS-CoV-2 variants is increasing, as reported in our study. Therefore, continuous monitoring of cases is necessary.

SARS-CoV-2 B.1.619 and B.1.620 Lineages, South Korea, 2021.

We report the rapid emergence of severe acute respiratory syndrome coronavirus 2 lineages B.1.619 and B.1.620 in South Korea. The surge in frequency in a relatively short time emphasizes the need for ongoing monitoring for new lineages to track potential increases in transmissibility and disease severity and reductions in vaccine efficacy.

SARS-CoV-2 main protease inhibition by compounds isolated from Luffa cylindrica using molecular docking.

In this study, chemical investigation of methanol extract of the air-dried fruits of Luffa cylindrica led to the identification of a new δ-valerolactone (1), along with sixteen known compounds (2-17). Their chemical structures including the absolute configuration were elucidated by extensive spectroscopic analysis and electronic circular dichroism analysis, as well as by comparison with those reported in the literature. For the first time in literature, we have examined the binding potential of the isolated compounds to highly conserved protein, Mpro of SARS-CoV-2 using the molecular docking technique. We found that the isolated saponins (14-17) bind to the substrate-binding pocket of SARS-CoV-2 Mpro with docking energy scores of -7.13, -7.29, -7.47, and -7.54 kcal.mol-1, respectively, along with binding abilities equivalent to an already claimed N3 protease inhibitor (-7.51 kcal.mol-1).