A Japanese study published on 3 October 2023 titled “Effects of tea, catechins and catechin derivatives on Omicron subvariants of SARS-CoV-2” by M. Shin‑Ya et al has found that tea can inactivate Omicron variants.
The researchers had previously found that tea ingredients did so for non-omicron variants.
[T]he tea catechin compound (−)- epigallocatechin gallate (EGCG) powerfully and rapidly inactivated the virus, which was also reported by other groups. Similar effects were also seen in black tea ingredients, galloylated theaflavins (theaflavin-3-O-gallate (TF3G), theaflavin-3’-O-gallate (TF3’G), and theaflavin-3,3’-Odigallate (TFDG)), and theasinensin A (TSA) that are derivatives of tea catechins. We also reported that the EGCG, TFDG and TSA interfered with the interaction between viral spike protein and ACE2 by binding to the spike protein receptor binding domain (RBD).
In short, not only are green tea, matcha green tea and black tea effective against omicron variants but also bottled green tea beverages given that their concentrations are lower. As expected, they are less effective.
Even candy containing green tea or black tea has an immediate effect, although this effect ceases within minutes.
The whole paper at merely 12 pages (and half of it are figures) is worth a read, but merely one figure is reproduced below.
On a related note, a study published on 23 January 2023 titled “Botanical inhibitors of SARS-CoV-2 viral entry: a phylogenetic perspective” by C.J. Risener et al found no few plant extracts that inhibit COVID-19 virus activity.
A total of 1867 extracts total from the QNPL derived from 660 species (1 Chromista, 27 Fungi, 632 Plantae kingdoms) across 149 families were screened for viral entry inhibition and mammalian cytotoxicity, as well as an additional 18 single compounds that are predominant in botanicals.
HCQ was used as a sort of control for comparison.
Of these, 310 extracts derived from 188 species across 76 families (3 fungi, 73 plants) exhibited ≥ 50% inhibition activity in the wild-type spike pseudotyped model (Fig. 1; Supplementary Materials 2–4). Of these bioactive extracts, 125 extracts derived from 93 plant species across 53 families exhibited ≥ 85% inhibition activity and ≤ 15% cytotoxicity in the wild-type model (Supplementary Material 2).
In particular, extract 1428 (Solidago altissima L., goldenrod flower), extract 1749 (Salix nigra Marshall, bark) and extract 1804 (Pteridium aquilinum (L.) Kuhn, fern Rhizomes) “demonstrated robust activity at lower concentrations, as well as minimal cytotoxicity at higher concentrations”.
Admittedly, determining the mechanism was beyond the scope of the study but at least the researchers have screened many and found no few as potential therapeutic applications.
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