Strictinin, a Major Ingredient in Yunnan Kucha Tea Possessing Inhibitory Activity on the Infection of Mouse Hepatitis Virus to Mouse L Cells

Abstract

Theacrine and strictinin of Yunnan Kucha tea prepared from a mutant variety of wild Pu’er tea plants were two major ingredients responsible for the anti-influenza activity. As the COVID-19 outbreak is still lurking, developing safe and cost-effective therapeutics is an urgent need. This study aimed to evaluate the effects of these tea compounds on the infection of mouse hepatitis virus (MHV), a β-coronavirus serving as a surrogate for SARS-CoV. Treatment with strictinin (100 μM), but not theacrine, completely eliminated MHV infection, as indicated by a pronounced reduction in plaque formation, nucleocapsid protein expression, and progeny production of MHV. Subsequently, a time-of-drug addition protocol, including pre-, co-, or post-treatment, was exploited to further evaluate the possible mechanism of antiviral activity mediated by strictinin, and remdesivir, a potential drug for the treatment of SARS-CoV-2, was used as a positive control against MHV infection. The results showed that all three treatments of remdesivir (20 μM) completely blocked MHV infection. In contrast, no significant effect on MHV infection was observed when cells were pre-treated with strictinin (100 μM) prior to infection, while significant inhibition of MHV infection was observed when strictinin was introduced upon viral adsorption (co-treatment) and after viral entry (post-treatment). Of note, as compared with the co-treatment group, the inhibitory effect of strictinin was more striking in the post-treatment group. These results indicate that strictinin suppresses MHV infection by multiple mechanisms; it possibly interferes with viral entry and also critical step(s) of viral infection. Evidently, strictinin significantly inhibited MHV infection and might be a suitable ingredient for protection against coronavirus infection.

Strictinin: A Key Ingredient of Tea

“…Searching for natural ingredients with a broad spectrum of antiviral activities might be an adequate solution for COVID-19 treatment. On the basis of their anti-influenza activities reported in the studies of Pu'er tea, theacrine, strictinin, and ellagic acid (thermally degraded product of strictinin) were subjected to the examination of their anti-coronavirus activities by using mouse hepatitis virus, a -coronavirus classified in the same subgenus as SARS-CoV and SARS-CoV-2 [20]. The inhibitory potency was monitored in three assays, plaque formation ability, viral protein production, and viral progeny.…”

Antiviral Activity of Anthranilamide Peptidomimetics against Herpes Simplex Virus 1 and a Coronavirus

“…MHV has been used as a model to investigate the effects of temperature and humidity on virus survival [ 9 ] and the efficacy of common disinfectants [ 10 , 11 ]. MHV has also been employed in evaluating the effectiveness of certain antiviral candidates [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. Currently, treatments for SARS-CoV-2 infection include molnupiravir, nirmatrelvir, ritonavir and remdesivir, but these are only recommended for people at high risk of severe infection [ 20 ].…”

“…The outbreak of the COVID-19 pandemic in 2019/2020 focused the world's attention on viral infections and the ease with which they can rapidly spread around the world. According to World Health Organization data, there have been at least 769,774,646 cumulative cases and 6,955,141 cumulative deaths from the SARS-CoV-2 virus that is the cause of COVID-19 (https://covid19.who.int, accessed on 19 August 2023) as of 16 August 2023. COVID-19 remains endemic in many countries in the world [1].…”