Background The derivatives of quercetin is known for their immune-modulating antiviral, anti-blood clotting, antioxidant, and also for its anti-inflammatory efficacy. The current study was therefore conducted to examine the noted novel derivatives of quercetin present in plant sources as an immune modulator and as an antiviral molecule in the COVID-19 disease and also to study their affinity of binding with potential three targets reported for coronavirus, i.e., papain-like protease, spike protein receptor-binding domain, and 3C-like protease. Based on the high-positive drug-likeness score, the reported derivatives of quercetin obtained from an open-source database were further filtered. Compounds with positive and high drug-likeness scores were further predicted for their potential targets using DIGEP-Pred software, and STRING was used to evaluate the interaction between modulated proteins. The associated pathways were recorded based on the Kyoto Encyclopedia of Genes and Genomes pathway database. Docking was performed finally using PyRx having AutoDock Vina to identify the efficacy of binding between quercetin derivatives with papain-like protease, spike protein receptor-binding domain, and 3C-like protease. The ligand that scored minimum binding energy was chosen to visualize the interaction between protein and ligand. Normal mode analysis in internal coordinates was done with normal mode analysis to evaluate the physical movement and stability of the best protein-ligand complexes using the iMODS server. Results Forty bioactive compounds with the highest positive drug-likeness scores were identified. These 40 bioactives were responsible for regulating different pathways associated with antiviral activity and modulation of immunity. Finally, three lead molecules were identified based on the molecular docking and dynamics simulation studies with the highest anti-COVID-19 and immunomodulatory potentials. Standard antiviral drug remdesivir on docking showed a binding affinity of − 5.8 kcal/mol with PLpro, − 6.4 kcal/mol with 3CLpro, and − 8.6 kcal/mol with spike protein receptor-binding domain of SARS-CoV-2, the discovered hit molecules quercetin 3-O-arabinoside 7-O-rhamnoside showed binding affinity of − 8.2 kcal/mol with PLpro, whereas quercetin 3-[rhamnosyl-(1- > 2)-alpha-L-arabinopyranoside] and quercetin-3-neohesperidoside-7-rhamnoside was predicted to have a binding affinity of − 8.5 kcal/mol and − 8.8 kcal/mol with spike protein receptor-binding domain and 3CLpro respectively Conclusion Docking study revealed quercetin 3-O-arabinoside 7-O-rhamnoside to possess the highest binding affinity with papain-like protease, quercetin 3-[rhamnosyl-(1- > 2)-alpha-L-arabinopyranoside] with spike protein receptor-binding domain, and quercetin-3-neohesperidoside-7-rhamnoside with 3C-like protease and all the protein-ligand complexes were found to be stable after performing the normal mode analysis of the complexes in internal coordinates. Graphical Abstract

The pandemic, which is brought about by the SARS CoV-2 infection, has inundated the entire world and obliterated the economies of numerous nations. Hence, looking for treatment and prophylaxis of COVID-19, Quercetin, which is a flavonoid gotten from plants and different sources like grapes, onion, tomatoes, apple, and so forth and has various properties like calming property, cardioprotective, and neuroprotective properties, is inspected for its antiviral properties, so it tends to be considered as one of the adjuvant medicines alongside the pharmacological medicines like Remdesivir and plasma treatment. A survey of the antiviral property of Quercetin from distributed articles proposes that Quercetin has a solid antiviral movement towards SARS C0V-2 and other upper respiratory tract infections. It can be securely and financially used to battle COVID-19. For high-hazard populaces, this medication can be a brilliant decision of treatment. Here the authors give proof to the utilization of Quercetin in relationship with pharmacological treatments like Remdesivir or improving plasma treatment.

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Ultra-performance liquid chromatography (UPLC) has an advantage over conventional High-performance liquid chromatography (HPLC) as UPLC offers substantial resolution, speed, and sensitivity during analysis. This advanced chromatographic technique uses sub-2μm particles for the stationary phase. As a result, it saves time and reduces solvent consumption, which allows it to take less run time and makes it highly efficient.

Dillenia indica is a well-known medicinal plant which thrives in varied agro-climates. It is native to Northeast India, but is widely distributed throughout the Himalayan range. Various studies on the plant reveals the presence of diverse biologically active chemical compounds associated with curing different ailments such as diabetes, inflammations, diarrhea, cancer, ulcer, microbial diseases, hematic disease, hepatic problems, dental problems, cardiovascular problems, hyperlipidmia and others. Most of the biological activities are contributed by the wide varieties of compounds present in fruit and leaves of D.indica. Various scientific investigations have proved that Proanthocyanidins and 3,5,7-Trihydroxy-2-(4'-hydroxybenzyl)-chroman-4-one present in the fruit of D.indica are responsible for minimizing the severity of diabetes and diabetic nephropathy. Betulinic acid isolated from D.indica has anticancer property. In addition to the therapeutic properties, the mucilage of D.indica is used as an important ingredient of various pharmaceutical formulations. Various factors affecting the chemical composition of D.indica such as temperature, annual season rainfall, pH, harvest date, climate, land and cultivation methods are discussed in this review. In view of the medicinal and pharmaceutical importance of the plant, it is quite worthy to review the active constituents and clinical effectiveness of D.indica.