Sophora interrupta Bedd. root-derived flavonoids as prominent antiviral agents against Newcastle disease virus.

The discovery and development of novel antiviral drugs from natural sources is continuously increasing due to limitations of currently available drugs such as toxic side effects, drug residue risk factors, high costs, and poor therapeutic strategies. Also, there are very few known antiviral drugs that are effective against only specific viruses. Hence, the present study is intended to isolate and characterize potent antiviral compounds from the methanolic root extract of Sophora interrupta Bedd. against avian paramyxovirus, Newcastle disease virus (NDV) and to distinguish the molecular basis of antiviral compounds. The two isolated flavonoids, maackiain (SR-1) and echinoisoflavanone (SR-2) exhibited the best antiviral activities against NDV infection in chicken embryo fibroblast cell lines compared to the standard antiviral drug, Ribavirin. Further, the in vitro studies and quantitative PCR analysis suggests that these flavonoids inhibit the viral entry, replication, and transcription, which may be beneficial as a promising strategy for the treatment of viral infections. Besides, the molecular docking studies of SR-1 and SR-2 exhibited high binding affinities of -7.6 and -8.0 kcal mol-1, respectively, and marked interactions with the NDV surface glycoprotein, hemagglutinin neuraminidase (HN). Also, the in silico toxicity properties as well pharmacokinetic studies of isolates revealed them as pharmacologically potent antiviral compounds.