Lactobacillus plantarum R-fermented Phellodendron amurense extract protects against PRV infection in vitro and in vivo by modulating oxidative stress and inflammatory responses

Pseudorabies virus (PRV) infection poses a significant health challenge to swine production, inducing oxidative stress, inflammatory responses, and reduced growth performance. Probiotic fermentation of medicinal plants is a promising strategy for generating novel probiotic-derived products for improving animal health. In this study, Phellodendron amurense (PA), a plant with both medicinal and dietary applications, was fermented with Lactobacillus plantarum R (LpR). We investigated the potential of fermented extract (FPAE) as a probiotic-derived feed additive for swine and its underlying mechanisms. Nontargeted UPLC‒MS/MS metabolomics revealed that fermentation significantly reshaped the metabolic profile of PAs, with marked enrichment of phenolic acids, flavonoids, and alkaloids. Specifically, the berberine content increased 2.5fold, and the levels of antioxidant components such as ferulic acid and kaempferol were significantly increased. In vitro, FPAE inhibited PRV replication in PK15 cells in a concentrationdependent manner (84.15% inhibition at 5 mg/mL). It also alleviated virusinduced oxidative stress, as evidenced by restored glutathione peroxidase (GSHPx) and superoxide dismutase (SOD) activities and reduced malondialdehyde (MDA) levels. The supernatant of LpR showed no antiviral activity, confirming that the enhanced efficacy resulted from biotransformation of the plant matrix. In vivo, daily oral administration of FPAE (125 mg/mL, 200 μL/mouse, equivalent to 892 mg/kg) significantly improved the survival rate (80% vs. 53.33% in the model group); increased the average daily weight gain and feed conversion ratio; reduced the viral loads in the brain, lung, spleen and kidney; and alleviated pathological damage to the brain and clinical symptoms. Furthermore, FPAE suppressed systemic inflammatory responses (decreased serum IL6, P <0.05) and enhanced antioxidant defense (increased GSHPx activity, P <0.05). Through a multidimensional “constituent–cell–animal” approach, this study demonstrated that probiotic fermentation restructures the chemical composition of Phellodendron amurense and synergistically regulates host oxidative stress and inflammatory responses to confer protection against viral infection. These findings provide a theoretical basis for developing LpRfermented Phellodendron amurense as a functional feed additive to control PRV infection in swine.