Investigation on the Inhibitory Effect of Bergenia purpurascens Water Extract on COVID-19 XBB1.5 Variant and Its Blocking ACE2 Mechanism

ObjectiveBergenia purpurascens, a medicinal herb indigenous to southwestern China, has garnered interest for its potential therapeutic properties. This study investigates the herb's water extract's capacity to interfere with the interaction between the COVID-19 S1 Receptor Binding Domain (RBD) and the ACE2 receptor, a critical step in the virus's infection process.MethodsQuality standards for the Bergenia purpurascens extract were established to ensure consistency. The extract's efficacy was assessed using a Vero-E6 cell infection model to inhibit live virus infection of the COVID-19 XBB1.5 variant. Surface Plasmon Resonance (SPR) was employed to explore the mechanism of action. The extract's composition was further analyzed using Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS), with active compounds identified through a combination of in silico screening and actual activity testing.ResultsThe water extract of Bergenia purpurascens demonstrated significant inhibitory activity against the COVID-19 XBB1.5 variant, with stability and high potency, reflected by an IC50 value of 0.037 mg/mL. The selectivity index for the antiviral effect is approximately 9. The extract's composition was predominantly Phenylpropanoids and Carbohydrates, accounting for over 60% of the total. Interestingly, a majority of the high-content compounds were inactive, while the low-content compounds, exemplified by Ellagic acid, showed synergistic activity. The extract's inhibitory mechanism was characterized as a non-specific inhibition of ACE2 with a steady-state binding affinity (KD) of 7.9 × 10−7 M.ConclusionsThe study concludes that the water extract of Bergenia purpurascens is a promising, cost-effective non-specific ACE2 inhibitor with potential applications in COVID-19 therapy. The identification of active compounds and the elucidation of its inhibitory mechanism provide a foundation for further research and development of this traditional medicinal herb in combating viral infections.