Objectives: The objective of this research was isolation and evaluation of xanthine oxidase inhibitory effects of isolated substances from mulberry bark (Morus alba L.). Methods: All four fractions: n-hexane, chloroform, ethyl acetate and water were evaluated for their effects on xanthine oxidase activity. The active compounds were isolated from the most potential fraction using column chromatography. The structures of these compounds were elucidated using ¹H and ¹³C-NMR and their xanthine oxidase inhibitory activities were evaluated spectrophotometrically. The pharmacokinetics parameters of the most promising substances were predicted using SwissADME tool. Results: Three compounds (Me01, Me02, Me04): ursolic acid Me01, oxyresveratrol Me02 andkuwanon G Me04 were isolated from ethyl acetate fraction. The xanthine oxidase activity assay showed that two compounds Me02 (oxyresveratrol) and Me04 (kuwanon G) both demonstrated inhibitory effects on xanthine oxidase with the IC₅₀ values of 42.08 µg/ml and 52.41 µg/ml, respectively. The predicted adsorption, distribution, metabolism and excretion (ADME) properties illustrated that oxyresveratrol (Me02) had high solubility in water, high gastro-intestinal (GI) absorption, no violation of Lipinski's rule of five and was not affected by P-glycoprotein, which is the cause of poor bioavailability of many drugs. Conclusion: Our findings suggest that oxyresveratrol is potent natural xanthine oxidase inhibitor in drug discovery and development for prevention and treatment of gout.