Xanthine Oxidase–Targeted and Antioxidant Effects of the PASA Polyherbal Formulation in Hyperuricemia: An Integrated in Silico and Experimental Study

Hyperuricemia is a metabolic condition characterized by abnormally elevated uric acid levels in the body, in which xanthine oxidase (XO) plays a key role. PASA is a traditional Vietnamese polyherbal formulation comprising Cortex Phellodendri, Rhizoma Atractylodis, Herba Sarcandrae , and Herba Achyranthis asperae . The aim of this study was to evaluate the anti-hyperuricemic activity of PASA using in silico, in vitro , and in vivo approaches. Reported phytochemicals were screened by molecular docking against XO (PDB ID: 3NVY). UPLC-QTOF/MS (ESI+) was used to profile the aqueous extract and tentatively characterize its major constituents. Antioxidant activity, XO inhibitory activity, acute oral toxicity, and anti-hyperuricemic activity were evaluated in vitro and in potassium oxonate-induced hyperuricemic mice. Molecular docking identified several alkaloids and flavonoids with high predicted affinity for XO. UPLC-QTOF/MS tentatively characterized 11 major constituents in the PASA extract. PASA exhibited antioxidant activity (IC 50 = 58.00 µg/mL) and XO inhibitory activity (IC 50 = 44.43 µg/mL) and showed no acute toxicity at 27.8 g/kg. Plasma uric acid concentrations were significantly reduced in hyperuricemic mice following repeated PASA administration. Linear mixed-effects model analysis demonstrated significant effects of treatment, time, and treatment × time interaction (all p < 0.001). Both PASA doses (0.695 and 1.39 g/kg) significantly reduced plasma uric acid versus the hyperuricemic model from Day 7 onward, while the higher dose showed no significant difference from allopurinol from Day 7 onward. PASA exhibited XO inhibitory and antioxidant activities in vitro and significantly reduced plasma uric acid concentrations in hyperuricemic mice without evidence of acute toxicity. These findings support further investigation of PASA as a potential intervention for hyperuricemia.