Notoginsenoside R1 Inhibits Porcine Deltacoronavirus Infection In Vitro by Restoring SERCA2-Mediated Calcium Homeostasis

Porcine coronavirus is one of the prevalent enteric coronaviruses in pigs, causing watery diarrhea and even death in suckling piglets and resulting in giant losses to the pig industry. However, effective antiviral strategies against PDCoV remain limited. Notoginsenoside R1 (NG-R1), a saponin extracted from Panax notoginseng, exhibits diverse bioactivities, but its antiviral potential has not been fully characterized. Herein, we systematically investigated the anti-PDCoV effect of NG-R1 and its underlying mechanism. NG-R1 showed no cytotoxic effect on LLC-PK1 cells and exerted antiviral ability against PDCoV infection through targeting the whole life cycle of the virus. In addition, network pharmacology analysis identified calcium signaling as a potentially relevant pathway involved in the antiviral activity of NG-R1. Further data demonstrated that PDCoV infection disrupted intracellular calcium homeostasis, whereas NG-R1 treatment partially restored calcium balance and attenuated endoplasmic reticulum (ER) stress. Moreover, NG-R1 modulated the expression of SERCA2, a key regulator of ER calcium transport. Thapsigargin, an inhibitor of SERCA2, showed similar antiviral capacity to NG-R1. Collectively, our findings suggest that NG-R1 exerts antiviral activity against PDCoV, potentially through regulation of calcium homeostasis mediated by SERCA2. This study provides a theoretical basis for the development of novel antiviral agents targeting calcium signaling pathways.