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Natural resources have largely been exploited for the past two decades regarding synthesis of novel drugs. The discovery of new plant-based therapeutic agents has witnessed an upsurge nowadays and many potent antimicrobial, antioxidant, antidiabetic, antitumor, and cytotoxic agents have been found. Nanoparticles derived from plants serve multiple purposes in biomedicine because of their tremendous ability to serve as reducing and stabilizing agents. The naturally existing flora is continuously being explored to evaluate their structural diversity and their possible applications in the field of nanotechnology. The nanodrugs or nanodrug delivery systems obtained by natural means are more stable, soluble, effective, biocompatible, and safe than chemically derived nanosystems. Bioinspired nanomaterials including metal/metal oxide nanoparticles and hybrid nanoparticles, obtained by green synthesis, are eco-friendly, nontoxic, and far more reliable to be employed in biomedicine. Moreover, the destructive effects of traditional synthesis approaches of nanomaterials have been minimized via green synthesis approach. Herein, we harness the green approach of nanoparticles’ fabrication utilizing plant extracts. Furthermore, applications of phytonanomaterials in biomedicine in the context of diverse biological activities have been described.

Background Starting December 2019, mankind faced an unprecedented enemy, the COVID-19 virus. The world convened in international efforts, experiences and technologies in order to fight the emerging pandemic. Isolation, hygiene measure, diagnosis, and treatment are the most efficient ways of prevention and intervention nowadays. The health organizations and global care systems screened the available resources and offered recommendations of approved and proposed medications. However, the search for a specific selective therapy or vaccine against COVID-19 remains a challenge. Methods A literature search was performed for the screening of natural and derived bio-active compounds which showed potent antiviral activity against coronaviruses using published articles, patents, clinical trials website (https://clinicaltrials.gov/) and web databases (PubMed, SCI Finder, Science Direct, and Google Scholar). Results Through the screening for natural products with antiviral activities against seven types of the human coronavirus, extracts of Lycoris radiata, Gentiana scabra, Dioscorea batatas, Cassia tora, Taxillus chinensis Cibotium barometz and Echinacea purpurea showed a promising effect against SARS-COV. Out of the listed compound Lycorine, emetine dihydrochloride hydrate, pristimerin, harmine, conessine, berbamine, 4`-hydroxychalcone, papaverine, mycophenolic acid, mycophenolate mofetil, monensin sodium, cycloheximide, oligomycin and valinomycin show potent activity against human coronaviruses. Additionally, it is worth noting that some compounds have already moved into clinical trials for their activity against COVID-19 including fingolimod, methylprednisolone, chloroquine, tetrandrine and tocilizumab. Conclusion Natural compounds and their derivatives could be used for developing potent therapeutics with significant activity against SARS-COV-2, providing a promising frontline in the fighting against COVID-19., Graphical Abstract Image, graphical abstract