Inflammation is a local reactions at the vascular tissue to injury that mediated by leukotriens. Leukotriens produced by lipoxygenase pathway, those can increase the permeability of capillaries and improves the adhesion of leukocytes to capillaries during injury or infection. Many kind of drugs for anti-inflamation are cyclooxygenase inhibitor. This research aimed to identify anti-inflammatory effect of Costus speciosus Smith. leaves through inhibition of lipoxygenase activity which tested by Spectrophotometer UV-Visible (λ=234 nm). Lipoxygenase enzyme inhibition test showed that n-hexane extract had IC50 2.4432 µg/mL, the ethyl acetate extract had IC50  0.0706 µg/mL, and ethanol extract IC50 0.4504 µg/mL. Ethyl acetate extract of Costus speciosus Smith. leaves has stronger inhibition of lipoxygenase compared to baikalein (IC50 = 0.240). Phytochemical screening showed that in ethyl acetate extract of Costus speciosus Smith. leaves contains flavonoids, saponins, hydroquinones, terpenoids, and steroids. It can be concluded that ethyl acetate extract of Costus speciosus Smith. leaves an extract of the most active in the inhibition of lipoxygenase activity.

Key Words            : lypoxygenase; antiinflamation; Costus speciosus Smith. leaves;

phytochemicals screening