The xanthine oxidase enzyme is an enzyme that catalyzes purine metabolic reactions, the oxidation of hypoxanthine to uric acid through xanthine compounds. High uric acid causes hyperuricemia. One treatment is to inhibit the xanthine oxidase enzyme. It can be conducted with a natural remedy, for example kaffir lime leaf extract. Research showed that kaffir lime leaves contain flavonoids that can inhibit the activity of the xanthine oxidase. This research aimed to examine kaffir lime leaf extract as an inhibitor of xanthine oxidase enzyme activity. Isolation of kaffir lime leaves was conducted by various maceration times of 24, 48, and 72 hours. The method of determining the inhibition value (IC50) of kaffir lime leaf extract to the xanthine oxidase enzyme was UV-Vis spectrophotometer at λ 291,5 nm. Maceration results of kaffir lime leaf extract with phytochemical tests for 48 hours showed that there were phenolic, flavonoids, steroids, alkaloids, tannins, and triterpenoids compounds. FT-IR test showed that there were C=O, C=C aromatic, O-H, and CH-aliphatic groups, which indicated the structure of the flavonoids. Maceration of kaffir lime leaf extract for 48 hours was a weak inhibitor with an IC50 value of 285,82 ppm.