Abstract
Background: Rapid spread of coronavirus infection and increased mortality rate in people with weaker immunity and co-morbidities has made the world petrified. Immunity plays a dominant role in fighting against COVID19. Siddha medicine, an indigenous system not only indicates curative but also preventive medicines that have immune-enhancing potential.

Materials and Methods: In Siddha literature, 20 medicinal plants have been indicated for fever, cough, throat infection, lung infection, respiratory diseases which can be correlated with the symptoms of COVID19. The following plants possessing rejuvenating potency were selected and reviewed for its immune-enhancing potentials. Terminalia chebula, Phyllanthus niruri, Zingiber officinale, Piper nigrum, Piper longum, Curcuma longa, Elletaria cardamomum, Cuminum cyminum, Tinospora cordifolia, Withania somnifera, Vitex negundo, Alpinia galanga, Phyllanthus emblica, Syzigium aromaticum, Alstonia scholaris, Andrographis paniculata, Euphorbiahirta, Allium sativum, Aloe barbadensis, Trigonella foenum graecum.

Results: Reviewed medicinal plants exhibited a good remedy for respiratory infections, inhibited the inflammatory cytokines, induced proliferation of lymphocytes, and enhanced both the innate and adaptive immunity thus improve host resistance.

Conclusion: 20 medicinal plants revealed immune-enhancing potentials. Among 20 medicinal plants Alpinia galanga, Allium Sativum, Andrographis paniculata, Curcuma longa, Phyllanthus emblica, shows profound effects on inflammatory cytokines, lymphopenia, decreases NLR (Neutrophil Lymphocyte Ratio) a marker of systemic inflammation in COVID19. Hence, these medicinal plants can alleviate the symptoms, improves the immune response, and might lower the mortality rate of COVID19. In the future, to establish a Polyherbal drug formulation for COVID19, these medicinal plants should undergo various research studies to explore its possible effects.

Results: Reviewed medicinal plants exhibited a good remedy for respiratory infections, inhibited the inflammatory cytokines, induced proliferation of lymphocytes, and enhanced both the innate and adaptive immunity thus improve host resistance.

Conclusion: 20 medicinal plants revealed immune-enhancing potentials. Among 20 medicinal plants Alpinia galanga, Allium sativum, Andrographis paniculata, Curcuma longa, Phyllanthus emblica, shows profound effects on inflammatory cytokines, lymphopenia, decreases NLR (Neutrophil Lymphocyte Ratio) a marker of systemic inflammation in COVID19. Hence, these medicinal plants can alleviate the symptoms, improves the immune response, and might lower the mortality rate of COVID19. In the future, to establish a Polyherbal drug formulation for COVID19, these medicinal plants should undergo various research studies to explore its possible effects.

Key words: COVID19, Immunoenhancers, Pandemic, Siddha medicinal plants