Chinese herbal extracts with antiviral activity: evaluation, mechanisms, and potential for preventing PRV, PEDV and PRRSV infections

The rapid expansion of large-scale pig farming has brought about a surge in viral diseases with high morbidity rates and diverse manifestations. This widespread occurrence of multiple viral diseases in pig farms has inflicted severe economic losses on the global swine industry. Consequently, there is an urgent need for eco-friendly and efficient antiviral drugs that can effectively combat viruses and prevent diseases such as PEDV, PRRSV, PRV, and other viral infections. To this end, we conducted a study on the antiviral activity and cytotoxicity of eleven different Chinese herbal extracts (CHE) against PRV. In vitro testing of several extracts, namely, Echinacea, Ilex purpurea Hassk, Ganoderma lucidum Kars, Taraxacum mongolicum, and Ilex rotunda Thunb, exhibited remarkable inhibition of PRV infection without causing any cytotoxic effects. Specifically, their antiviral selectivity indexes were significantly higher, with values ranging from 6- to 144-fold. The antiviral efficacy of five CHEs was evaluated against other RNA viruses, including PRRSV and PEDV. The extracts showed substantial inhibition of PEDV and PRRSV proliferation. Echinacea and Ilex purpurea Hassk extracts exhibited the highest virus inhibitory effects. To understand the antiviral mechanisms underlying their potent activity, a time-of-addition experiment was conducted. The results indicated that these extracts effectively targeted the early infection and postinfection stages of PRV, PEDV, and PRRSV. The study found that the Chinese herbal extracts, Echinacea and Ilex purpurea Hassk, had both direct and indirect effects on virus particles and cellular targets, demonstrating broad-spectrum antiviral activity against multiple clinical strains of PRV and PEDV. These findings provide a strong foundation for the development of herbal medicines to prevent and treat infections caused by PRV, PEDV and PRRSV in the swine industry. The identified extracts show great promise for the formulation of effective and environmentally friendly antiviral interventions. Graphical Abstract