Hemorrhagic transformation(HT)is a common serious complication of stroke after thrombolysis treatment,which limits the clinical use of tissue plasminogen activator(t-PA).Since early diagnosis and treatment for HT is important to improve the prognosis of stroke patients,it is urgent to discover the potential biomarkers and therapeutic drugs.Recent evidence shows that pinocembrin,a natural flavonoid compound,exerts anti-cerebral ischemia effect and expands the time window of t-PA.In this study,we investigated the effect of pinocembrin on t-PA-induced HT and the potential biomarkers for HT after t-PA thrombolysis,thereby improving the prognosis of stroke.Electrocoagulation-induced thrombotic focal ischemic rats received intravenous infusion of t-PA(10 mg/kg)6h after ischemia.Administration of pinocembrin(10 mg/kg,iv)prior t-PA infusion significantly decreased the infarct volume,ameliorated t-PA-induced HT,and protected blood-brain barrier.Metabolomics analysis revealed that 5 differential metabolites in the cerebral cortex and 16 differential metabolites in serum involved in amino acid metabolism and energy metabolism were significantly changed after t-PA thrombolysis,whereas pinocembrin administration exerted significant intervention effects on these metabolites.Linear regression analysis showed that lactic acid was highly correlated to the occurrence of HT.Further experiments confirmed that t-PA treatment significantly increased the content of lactic acid and the activity of lactate dehydrogenase in the cerebral cortex and serum,and the expression of monocarboxylate transporter 1(MCT 1)in the cerebral cortex;pinocembrin reversed these changes,which was consistent with the result of metabolomics.These results demonstrate that pinocembrin attenuates HT after t-PA thrombolysis,which may be associated with the regulation of endogenous metabolites.Lactic acid may be a potential biomarker for HT prediction and treatment.