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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, has been a global concern. While there have been some vaccines and drugs, the rapid emergence of variants due to mutations has threatened public health. As the de novo drug development process is expensive and time-consuming, repurposing existing antiviral drugs against SARS-CoV-2 is an alternative and promising approach to mitigate the current situation. Several studies have indicated that some natural products exhibit inhibitory activities against SARS-CoV-2. This study is aimed at analyzing the potential of natural alkaloids, using various computational tools, as drug candidates against SARS-CoV-2. The molecular docking analysis predicted that naturally occurring alkaloids can bind with RNA-dependent RNA-polymerase (RdRP). The QSAR analysis was conducted by using the way2drug/PASS online web resource, and the pharmacokinetics and toxicity properties of these alkaloids were predicted using pkCSM, SwissADME, and ProTox-II webserver. Among the different alkaloids studied, neferine and berbamine were repurposed as potential drug candidates based on their binding affinity and interactions with RdRP. Further, molecular dynamics simulation of 90 ns revealed the conformational stability of the neferine-RdRP complex.

Traditional herbal medicines have been consumed in Nepal and other parts of the eastern hemisphere since ancient times. Many of these plants reportedly have been effective against ailments as well. This study aims to analyze the phytochemical constituents from the extracts of ten such plants and evaluate their antimicrobial, cytotoxicity, and antioxidant properties. In addition, the study aims to study the correlation of cytotoxicity and antioxidant activities with the total phenolic, flavonoid, and tannin contents. The plants investigated were Oroxylum indicum, Kalanchoe pinnata, Phragmites vallatoria, Ehretia acuminata, Cirsium wallichii, Ampelocissus tomentosa, Dichrocephala integrifolia, Boenninghausenia albiflora, Cynoglossum zeylanicum, and Clerodendrum serratum. Phytochemical analyses were performed to evaluate secondary metabolites, such as glycosides, flavonoids, terpenoids, saponins, alkaloids, and fats. The total phenolic contents of the extracts ranged from 14.94 to 229.89 mg GAE/g, the total flavonoid contents varied from 66.67 to 900 mg QE/g, and the total tannin contents were 42 to 168 mg GAE/g. The results of the antioxidant studies showed that the highest antioxidant activity was exhibited by the extract of A. tomentosa (IC50 = 7.89 µg/mL) followed by E. acuminata (IC50 = 24.82 µg/mL) and C. serratum (IC50 = 32.91 µg/mL). The extracts from P. vallatoria and A. tomentosa exhibited substantial antimicrobial activity. The extracts of A. tomentosa and B. albiflora showed lethality against brine shrimp with LC50 values of 33.11 µg/mL.