In-vitro antiviral activity of Neem (Azadirachta indica L.) Bark extract against BCoV, BHV-1, BPIV-3, and BEVs

Neem extracts and bioactive compounds which have been widely utilized in medicine for some time, exhibit regulatory effects in relation to various biological mechanisms, and include antioxidant, anti-inflammatory, antihyperglycemic, as well as antifungal, antibacterial, and antiviral properties. Thus, this clearly underscores the pivotal role of Neem Bark in modulation of various biological pathways. The present study evaluated the antiviral activity of Azadirachta indica (Neem Bark) extract on Bovine Corona Virus (BCoV), Bovine Herpes Virus-1 (BHV-1), Bovine Parainfluenza Virus-3 (BPIV-3) and Bovine Entero Virus (BEV) in vitro. The aim of the present study was to determine whether its antiviral activities were effective in the cell entry or replication phase of each virus. As a result of the WST-1 test, performed to determine the non-cytotoxic dose of NBE, it was determined that concentrations lower than 0.87 mg/mL were not cytotoxic in an MDBK cell line. Although Neem Bark extract (NBE) did not have any significant effect on the attachment of Bovine Parainfluenza Virus-3 and Bovine Entero Virus to the host cell, a 100-fold decrease in TCID50 (50% tissue culture infectious dose) values of Bovine Corona Virus treated with Neem extract was detected, and virus replication was completely blocked in Bovine Herpes Virus-1. In conclusion, we suggest that it would be valuable to evaluate its antiviral activity on Bovine Corona Virus and Bovine Herpes Virus-1 in vivo. Additionally, the detailed determination of the effectiveness of NBE against other viruses would contribute to future antiviral drug trials.