SARS-CoV-2 omicron variants are susceptible in vitro to Artemisia annua hot water extracts

ETHNOPHARMACOLOGICAL RELEVANCE: Artemisia annua L. has >2000 yr of history in treating fever a symptom common to many infectious diseases including viruses. The plant is widely used as a tea infusion in many areas of the globe to thwart many infectious diseases. AIM OF THE STUDY: The SARS-CoV-2 (COVID-19) virus continues to infect millions while rapidly evolving new variants that are more transmissible and evade vaccine-elicited antibodies, e.g., omicron and its subvariants. Having shown potency against all previously tested variants, A. annua L. extracts were further tested against highly infectious omicron and its recent subvariants. MATERIALS AND METHODS: Using Vero E6 cells, we measured the in vitro efficacy (IC(50)) of stored (frozen) dried-leaf hot-water A. annua L. extracts of four cultivars (A3, BUR, MED, and SAM) against SARS-CoV-2 variants: original WA1 (WT), BA.1 (omicron), BA.2, BA.2.12.1, and BA.4. End point virus titers of infectivity in cv. BUR-treated human lung A459 cells overexpressing hu-ACE2 were determined for both WA1 and BA.4 viruses. RESULTS: When normalized to the artemisinin (ART) or leaf dry weight (DW) equivalent of the extract, the IC(50) values ranged from 0.5 to 16.5 μM ART and from 20 to 106 μg DW. IC(50) values were within limits of assay variation of our earlier studies. End-point titers confirmed a dose-response inhibition in ACE2 overexpressing human lung cells to the BUR cultivar. Cell viability losses were not measurable at leaf dry weights ≤50 μg for any cultivar extract. CONCLUSIONS: A. annua hot-water extracts (tea infusions) continue to show efficacy against SARS-CoV-2 and its rapidly evolving variants and deserve greater attention as a possible cost-effective therapeutic.