Antiviral activity of Rumex crispus extract and its bioactive constituent emodin against human coronavirus OC43

Coronaviruses are responsible for diseases ranging from mild respiratory symptoms to severe infections such as COVID-19. Despite the availability of vaccines and therapeutic agents, the emergence of new variants and drug-resistant strains highlights the need for additional antiviral strategies. In this study, Rumex crispus was investigated as a potential source of antiviral compounds. The ethanol (EtOH) extract of R. crispus roots was prepared and subsequently fractionated into n-hexane (n-hex), ethyl acetate (EA), and aqueous fractions. Among these, the n-hexane and EA fractions exhibited significant antiviral activity against human coronavirus OC43, as demonstrated by Western blot, qRT-PCR, and plaque assays. Chemical analysis of the extract by HPLC led to the identification of epicatechin, naphthalene derivatives, and anthraquinones. Notably, emodin, an anthraquinone, showed pronounced antiviral activity, and was found to be enriched in the active n-hexane and EA fractions. These findings suggest that emodin may contribute to the antiviral activity of R. crispus extract, although the potential involvement of other bioactive constituents cannot be excluded.