Anti-Viral Properties of Herbs
Many herbs are known to have anti-viral properties, and in this article we will explore several keys herbs that may be useful in treating coronavirus. This article is written in a way that explores the biochemistry of plant compounds, and draws from a number of research studies.
One herb used in the late stage treatment of COVID-19 is Huang qin (Scutellariae) and it is known to contain a substance called baicalin. This substance also has a patent for the treatment of SARS, which is another virus in the family of corona viruses. The following is from the PubChem National Institute of Health Government site, concerning a patent for baicalin.
"The present invention relates to a pharmaceutical composition useful for the treatment of diseases associated with viruses of the order Nidovirales of the family Coronaviradae, such as Severe Acute Respiratory Syndrome (SARS) viruses in humans and other animals. In particular, this invention relates to a naturally occurring compound, namely, baicalin, extracted and purified from the Chinese medicinal plant Scutellaria baicalensis Georgi (Chinese name: Huang Qin), that exhibits potent antiviral activity against members of the order Nidovirales of the family Coronaviradae that infects humans and other animals..." To read more about this patent follow this link. (Baicalin as a treatment for SARS infection)
In Traditional Chinese Medicine (TCM) the herb containing baicalin (Huang qin, Scutellariae) is used in an herbal formula called Xiao Chai Hu Tang, and would be used for middle stage infection, just after the initial symptoms and as the disease penetrates to a deeper level within the lungs. It can also be used for pneumonia, but would usually be combined with other medications such as Houtuyynia cordata (You Xing Cao).
Recent research on Chinese herbal medicine for coronavirus has analyzed how various biochemicals work on a molecular level.  The herb Scutellariae has been shown to, "inhibit nsP13 by affecting the ATPase activity." 
Other researchers have examined the anti-viral effects of Scutellaria and its chemical compounds, and the research has been nicely summarized on www.drugs.com, which states:
"A flavonoid compound from Scutellariae baicalensis inhibited T-cell leukemia virus type Ι (HTLV-Ι). Constituent baicalin inhibited reverse transcriptase activity in HTLV-Ι-infected cells, as well as the activity of purified reverse transcriptase from Moloney murine leukemia virus and Rous-associated virus type 2.  Other flavones, such as isoscutellarein from S. baicalensis leaves, also showed anti-influenza virus activity in vitro.  Isoscutellarein-8-methylether from S. baicalensis roots had effects against influenza A and B viruses, with results suggesting inhibition of the replication of A/Guizhou and B/Ibaraki viruses by inhibiting the fusion of viral envelopes with the endosome/lysosome membrane that occur in the early stage of the virus infection cycle. "
As coronavirus uses RNA polymerase to replicate itself, research on the herb Houttuynia cordata may offer some solutions as its been shown to, "inhibit the viral SARS-3CL proactivity, block viral RNA‑dependent RNA polymerase activity (RdRp) Immunomodulation." [1, 6, 7]
From a Chinese medicine perspective using Huang qin (Scutellariae) in combination with Yu Xing Cao (Houttuynia), would be a logical choice as both plants reduce heat and damp, or what we may think of as inflammation in Western medical terms. As pneumonia is an inflammation of the alveoli, reducing damp-heat (inflammation) in the lungs is a standard treatment protocol from a Chinese medicine perspective.
As Chinese medicine uses many herbs in combination to treat various conditions, clinicians find that by combining herbs they are able to draw on numerous benefits of a variety of plant medicines. For instance, for prevention the formulas Yu Ping Fen San and Sang Ju Yin Tang are used together by high risk hospital and research staff. According to Yang, "Lau and colleagues reported that, during SARS outbreak, 1063 volunteers including 926 hospital workers and 37 laboratory technicians working in high-risk virus laboratories used a TCM herbal extract, namely Sang Ju Yin plus Yu Ping Feng San. Compared with the 0.4% of infection in the control group, none of TCM users infected." (1).
According to TCM infectious diseases with fever can be understood in four stages, and one of these models posits the first stage to be prevention. The herbal formula Yu Ping Feng San is widely known to be used to boost and modulate the immune system, and in the case of coronavirus, is used with formulas like Sang Ju Yin or Yin Qiao San to prevent infection. To learn more about using these medicines for prevention fo coronavirus go to: Chinese Herbs for the Prevention of Corona Virus.
1. Yang Yang, Md Sahidul Islam, Jin Wang, Yuan Li, and Xin Chen. Traditional Chinese Medicine in the Treatment of Patients Infected with 2019-New Coronavirus (SARS-CoV-2): A Review and Perspective, Int J Biol Sci. 2020; 16(10): 1708–1717. Published online 2020 Mar 15.
2. Yu MS, Lee J, Lee JM, Kim Y, Chin YW, Jee JG. et al. Identification of myricetin and scutellarein as novel chemical inhibitors of the SARS coronavirus helicase, nsP13. Bioorg Med Chem Lett. 2012;22:4049–54.
3. Baylor NW, Fu T, Yan YD, Ruscetti FW. Inhibition of human T cell leukemia virus by the plant flavonoid baicalin (7-glucuronic acid, 5,6-dihydroxyflavone). J Infect Dis. 1992;165(3):433-437.1371535
4. Nagai T, Miyaichi Y, Tomimori T, Suzuki Y, Yamada H. In vivo anti-influenza virus activity of plant flavonoids possessing inhibitory activity for influenza virus sialidase. Antiviral Res. 1992;19(3):207-217.1444327
5. Nagai T, Suzuki Y, Tomimori T, Yamada H. Antiviral activity of plant flavonoid, 5,7,4′-trihydroxy-8-methoxyflavone, from the roots of Scutellaria baicalensis against influenza A (H3N2) and B viruses. Biol Pharm Bull. 1995;18(2):295-299.7742801
6. Fung KP, Leung PC, Tsui KW, Wan CC, Wong KB, Waye MY. et al. Immunomodulatory activities of the herbal formula Kwan Du Bu Fei Dang in healthy subjects: a randomised, double-blind, placebo-controlled study. Hong Kong Med J. 2011;17(Suppl 2):41–3.
7. Lau KM, Lee KM, Koon CM, Cheung CS, Lau CP, Ho HM. et al. Immunomodulatory and anti-SARS activities of Houttuynia cordata. J Ethnopharmacol. 2008;118:79–85.