The world pandemic COVID-19 caused by SARS-CoV-2 is currently claiming thousands of lives. Flavonoids abundantly present in the fruits and vegetables, especially quercetin, are shown to have antiviral activities. This paper reviews the capability of the plant flavonoid quercetin to fight the novel coronavirus and the possibility for drug development based on this. The mode of action explaining the known pathways through which this molecule succeeds in the antiviral activity, action of quercetin on SARS-CoV-2 main protease 3CLpro, antiviral activities of its derivatives on human viruses, effect of combination of zinc co-factor along with quercetin in the COVID-19 treatment, and the regulation of miRNA genes involved in the viral pathogenesis are discussed. Proof for this concept is provided following the virtual screening using ten key enzymes of SARS-CoV-2 and assessing their interactions. Active residues in the 3D structures have been predicted using CASTp and were docked against quercetin. Key proteins 3CLpro, spike glycoprotein/ human ACE2-BOAT1 complex, RNA-dependent RNA polymerase, main peptidase, spike glycoprotein, RNA replicase, RNA binding protein, papain-like protease, SARS papain-like protease/ deubiquitinase, and complex of main peptidase with an additional Ala at the N-terminus of each protomer, have shown the binding energies ranging between − 6.71 and − 3.37 kcal/ Mol, showing that quercetin is a potential drug candidate inhibiting multiple SARS-CoV-2 enzymes. The antiviral properties of flavonoid and the molecular mechanisms involved are reviewed. Further, proof for this concept is given by docking of key proteins from SARS-CoV-2 with quercetin.

中文翻译：

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对基于植物类黄酮槲皮素的新型 SARS-CoV-2 药物的展望

由 SARS-CoV-2 引起的全球大流行 COVID-19 目前正在夺去数千人的生命。大量存在于水果和蔬菜中的类黄酮，尤其是槲皮素，被证明具有抗病毒活性。本文就植物黄酮类槲皮素抗击新型冠状病毒的能力以及在此基础上开发药物的可能性进行综述。作用方式解释了该分子成功实现抗病毒活性的已知途径，槲皮素对 SARS-CoV-2 主要蛋白酶 3CLpro 的作用，其衍生物对人类病毒的抗病毒活性，锌辅因子与讨论了槲皮素在 COVID-19 治疗中的作用，以及参与病毒发病机制的 miRNA 基因的调节。在使用 SARS-CoV-2 的十种关键酶进行虚拟筛选并评估它们的相互作用后，提供了这一概念的证据。使用 CASTp 预测了 3D 结构中的活性残基，并与槲皮素对接。关键蛋白3CLpro、刺突糖蛋白/人ACE2-BOAT1复合物、RNA依赖性RNA聚合酶、主肽酶、刺突糖蛋白、RNA复制酶、RNA结合蛋白、木瓜蛋白酶、SARS木瓜蛋白酶/去泛素酶、主肽酶复合物在每个原体的 N 末端有一个额外的 Ala，显示出结合能在 - 6.71 和 - 3.37 kcal/Mol 之间，表明槲皮素是抑制多种 SARS-CoV-2 酶的潜在候选药物。对黄酮类化合物的抗病毒特性及其所涉及的分子机制进行了综述。更远，