Virus Antioxidant Effects Ref Rhinovirus Glutathione Scavenge free radicals and suppress NF-κBinduced Intercellular adhesion molecule-1 (ICAM-1) receptor for rhinovirus [84] Pyrrodolinedithiocarbonate (PDTC) Inhibited viral replication in vitro [93] Influenza Virus Thiol antioxidants Pyrrodolinedithiocarbonate (PDTC) Scavenge OH- free radicals and Inhibited synthesis negative strand RNA and viral replication in vitroand in vivo [72,94] N-Acetyl-L-cysteine (NAC) Inhibited induction of apoptosis and pro-inflammatory cytokines such as IL-6, IL-8 and RANTES [95,96] Glutathione Inhibited induction of apoptosis and viral replication in vitroand in vivo [97,98] Hydroxyl antioxidants/Polyphenols Nordihydroguaiaretic acid (NDGA) scavenge O2-, OH-radicals and H2O2 and Inhibited viral replication through inhibiting intracellular transport of viral glycoproteins   [99-104] Thujaplicin Inhibited induction of apoptosis and viral replication in vitro [100] Resveratrol Blocked nuclear cytoplasmic translocation viral ribonucleoproteins and reduced expression of late viral proteins and resulted in reduced viral replication in vitroand in vivo [101] Ambroxol Suppressed proliferation of virus in vivo [103] Ascorbic acid inhibited the proliferation of virus in vitro [104]  Flavonoids Catechins Scavenge O2- and Inhibited viral replication by inhibiting activities of hemagglutininn, neuraminidase and suppressing viral RNA synthesis in in vitro and in vivo   [105-107] Quercetin 3-rhamnoside Inhibited viral replication by inhibiting viral mRNA synthesis [106] Isoquercetin Inhibited viral replication and pro-inflammatory cytokines [107] Antioxidant enzymes SOD, Catalase scavenge O2-/OH- free radicals; restores redox status in vitro and in vivo; enhances recovery [70,108-111] Nrf2 inducers Sulforaphane antiviral activity [39] RSV Thiols NAC scavenge H2O2, OH-free radicals, and hypochlorous acid; suppress NF-κB activation and viral replication [51,112] Polyphenols Resveratrol reduced IFN-γ levels associated with RSV-mediated airway inflammation and AHR; inhibit TRIF signaling pathway   [113,114] SOD significantly reduced pulmonary viral titers [73] SOD Mimetics scavenge ROS and inhibit chemokine secretion in vitro [8,78] Nrf2 inducers Sulforaphane BHA and tBHQ antiviral activity in mouse; scavenge ROS by inducing expression of antioxidant enzymes and inhibit chemokine secretion in vivo and in vitro; mice treated with BHA recovered faster [61,69] Casola A, (unpublished observation)

Table 3: Antioxidant therapy against respiratory viruses.