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This study was conducted to investigate student barriers to the prospect of online learning in Vietnam, in the context of Covid-19 pandemic. This mixed-method study attracted the participation of 1165 students from twelve universities and nine high schools across thirteen provinces in the Mekong Delta. The findings revealed the additional three obstacles from the qualitative data analysis including (1) geographical features, (2) the economic status of Vietnamese people, and (3) Vietnamese culture and traditions in addition to the six groups of barriers being re-confirmed from Berge's framework (2005). The results of Binary Logistic Regression testified the negative impacts of obstacles in Learner Motivation, Cost and Access to the Internet, and Social Interaction on the prospects of online learning, though it is predicted to go farther in education in Vietnam in the future.

New metabolites, xiamycins C-E (1-3), were isolated from a Streptomyces. sp (#HK18) culture inhabiting the topsoil in a Korean solar saltern. The planar structures of the xiamycins C-E were elucidated as carbazole-bearing indolosesquiterpenoids using a combined analysis of NMR, MS, UV, and IR spectroscopic data. The absolute configurations of these new compounds were determined by analyses of NOESY and ECD data. When the xiamycins were tested for inhibitory activity on porcine epidemic diarrhea virus (PEDV), xiamycin D (2) showed the strongest inhibitory effect on PEDV replication (EC50 = 0.93 μM) with low cytotoxicity (CC50 = 56.03 μM), thus displaying a high selective index (60.31). Quantitative real-time PCR data revealed the inhibitory effect of 2 on genes encoding essential structural proteins (GP6 nucleocapsid, GP2 spike, and GP5 membrane) for PEDV replication in a dose-dependent manner. The antiviral activity of xiamycin D (2) was also supported by both Western blotting of the GP2 spike and GP6 nucleocapsid protein synthesis of PEDV. Therefore, xiamycin D shows the potential of indolosesquiterpenoids as new and promising chemical skeletons against PEDV-related viruses.

Ecklonia cava is edible seaweed that is found in Asian countries, such as Japan and Korea; and, its major components include fucoidan and phlorotannins. Phlorotannins that are isolated from E. cava are well-known to have an antioxidant effect and strong antiviral activity against porcine epidemic diarrhea virus (PEDV), which has a high mortality rate in piglets. In this study, the bioactive components were determined based on two different approaches: (i) bio-guided isolation using the antiviral activity against the H1N1 viral strain, which is a representative influenza virus that originates from swine and (ii) high-resolution mass spectrometry-based dereplication, including relative mass defects (RMDs) and HPLC-qTOFMS fragmentation analysis. The EC70 fraction showed the strongest antiviral activity and contained thirteen phlorotannins, which were predicted by dereplication. Ten compounds were directly isolated from E. cava extract and then identified. Moreover, the dereplication method allowed for the discovery of two new phlorotannins. The structures of these two isolated compounds were elucidated using NMR techniques and HPLC-qTOFMS fragmentation analysis. In addition, molecular modelling was applied to determine the absolute configurations of the two new compounds. The antiviral activities of seven major phlorotannins in active fraction were evaluated against two influenza A viral strains (H1N1 and H9N2). Six of the compounds showed moderate to strong effects on both of the viruses and phlorofucofuroeckol A (12), which showed an EC50 value of 13.48 ± 1.93 μM, is a potential active antiviral component of E. cava.

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