Background: Inhibition of arginase activity can ameliorate endothelial dysfunction in vascular system which can cause some cardiovascular diseases. This study was aimed to test the arginase activity inhibition of n-hexane, ethyl acetate, and methanol extract of C. pulcherrima (L.) Sw. stem bark and determine total flavonoid content of the most active extract. Methods: C. pulcherrima (L.) Sw. stem bark was extracted using multistage reflux. In vitro arginase activity inhibition was done using 1 U/mL enzyme concentration and 570 mM substrate concentration. The product was measured by microplate reader of wavelength 430 nm. Results: Methanolic extract showed to be the most active extract in the test. IC50 value of methanolic extract was 21.969 μg/mL which was higher than standard N(omega)-hydroxy-nor-L-arginine acetate (nor-NOHA acetate) that had IC50 value of 3.994 μg/mL. The result of total flavonoid content determination of methanol extract by colorimetric AlCl3 was 3.943 mgQE/gram extract. Phytochemical screening shows that methanol extract of C. pulcherrima (L.) Sw. stem bark contains flavonoids, tannins, saponins, and triterpenoids. Conclusion: Methanol extract of C. pulcherrima (L.) Sw. had significant inhibitory activity of arginase and can be used as a potential source for the development of arginase inhibitor.
Key words: Arginase, Caesalpinia pulcherrima (L.) Sw. stem bark, Total flavonoid content, Phytochemical screening.