Bis-Benzylisoquinoline Alkaloids Inhibit Porcine Epidemic Diarrhea Virus by Disrupting Virus Entry

The porcine epidemic diarrhea virus (PEDV), belonging to the α-coronavirus, is the causative agent of porcine epidemic diarrhea (PED). Presently, protection from the existing PEDV vaccine is not effective. Therefore, anti-PEDV compounds should be studied. Berbamine (BBM), Fangchinoline (FAN), and (+)-Fangchinoline (+FAN), are types of bis-benzylisoquinoline alkaloids that are extracted from natural medicinal plants. These bis-benzylisoquinoline alkaloids have various biological activities, including antiviral, anticancer, and anti-inflammatory properties. In this study, we found that BBM, FAN, and +FAN suppressed PEDV activity with a 50% inhibitory concentration of 9.00 µM, 3.54 µM, and 4.68 µM, respectively. Furthermore, these alkaloids can decrease the PEDV-N protein levels and virus titers in vitro. The time-of-addition assay results showed that these alkaloids mainly inhibit PEDV entry. We also found that the inhibitory effects of BBM, FAN, and +FAN on PEDV rely on decreasing the activity of Cathepsin L (CTSL) and Cathepsin B (CTSB) by suppressing lysosome acidification. Taken together, these results indicated that BBM, FAN, and +FAN were effective anti-PEDV natural products that prevented PEDV entry and may be considered novel antiviral drugs.