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Emerging variants of the virus are characterized by higher transmission rates and immune escape mutations, enabling them to evade vaccine-induced immunity. Existing treatment options, including monoclonal antibodies, are often variant-specific and not widely accessible, especially in low- and middle-income countries. Natural compounds derived from medicinal herbs and green tea have demonstrated antiviral activity against various viruses and may offer promising, variant-independent therapeutic potential.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In this study, we examined the antiviral activity of four plant-derived compounds: glycyrrhizin, curcumin, harmaline, and (-)-epigallocatechin. The compounds were tested in vitro against SARS-CoV-2 D614G, Omicron BA.5, and Omicron XBB.1. The antiviral efficacy was assessed at subtoxic concentrations to evaluate potential therapeutic applicability.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>All tested compounds showed effective neutralization of SARS-CoV-2 D614G, Omicron BA.5, and Omicron XBB.1 at subtoxic concentrations. In particular, glycyrrhizin, curcumin, and harmaline exhibited potent antiviral activity across all tested variants.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Our findings support the potential of glycyrrhizin, curcumin, and harmaline as variant-independent treatment candidates for COVID-19. However, further clinical studies are necessary to validate their efficacy and safety in vivo.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s12906-026-05253-1","type":"journal-article","created":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T18:17:21Z","timestamp":1769105841000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Dose-dependent antiviral effects of glycyrrhizin, curcumin, and harmaline against clinical SARS-CoV-2 isolates, including D614G, Omicron BA.5, and Omicron XBB.1"],"prefix":"10.1186","volume":"26","author":[{"given":"Rabea","family":"Gr\u00fcneberg","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Isabel","family":"Zydek","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carina","family":"Elsner","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Evelyn","family":"Scheiermann","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ulf","family":"Dittmer","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Folker","family":"Meyer","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ivana","family":"Kraiselburd","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hana","family":"Rohn","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Oliver","family":"Witzke","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laura","family":"Th\u00fcmmler","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Adalbert","family":"Krawczyk","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,1,22]]},"reference":[{"key":"5253_CR1","doi-asserted-by":"publisher","unstructured":"Panneer S, Kantamaneni K, Akkayasamy VS, Susairaj AX, Panda PK, Acharya SS, et al. 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