Dose-dependent antiviral effects of glycyrrhizin, curcumin, and harmaline against clinical SARS-CoV-2 isolates, including D614G, Omicron BA.5, and Omicron XBB.1.

BACKGROUND: SARS-CoV-2 remains a major global health challenge, as infection can lead to potential life-threatening conditions such as COVID-19. 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.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.