Kakkonto, shosaikoto, Platycodon grandiflorum root, and gypsum (a Japanese original combination drug known as saikatsugekito): Pharmacological review of its activity against viral infections and respiratory inflammatory conditions and a discussion of its applications to COVID‐19

AIM: Traditional Japanese (Kampo) medicine has been used to treat viral infectious diseases. In particular, saikatsugekito (a combination drug of kakkonto, shosaikoto, Platicodon glandiflorum root, and gypsum) has been reported to be useful during the past influenza pandemic. The severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has spread worldwide, causing the novel coronavirus disease (COVID‐19) to emerge as a pandemic. In this article, we conducted a literature review on the pharmacological activities of the components present in saikatsugekito against viral infection and respiratory inflammation. METHODS: We searched PubMed and the Cochrane Library for English articles, as well as Ichushi and J‐stage for Japanese articles. Articles published until January 1, 2000 were retrieved using the keywords ‘kakkonto’, ‘shosaikoto’, ‘Platycodon’, and ‘gypsum’. We then extracted articles on basic research investigating viral infections, inflammation, cytokine, the immune response, and lung tissue damage. RESULTS: We extracted 28 eligible articles. Kampo medicines have antiviral activities by interfering with the attachment, internalization, replication, progeny virion release, and cell‐to‐cell spreading of single‐strand RNA viruses. They also enhance the immunomodulating activities of the host, including cytokine production, regulation of multiple immune cells, and protection from lung tissue injury. Furthermore, Kampo medicine has been found to regulate body temperature and airway mucin release. CONCLUSION: The results demonstrated that Kampo medicine has therapeutic activities against single‐strand RNA virus infections and respiratory inflammation, and may also have activities against SARS‐CoV‐2. Further research is required to investigate the activity of Kampo medicines, such as saikatsugekito, against SARS‐CoV‐2.