The Itchy leaf [Laportea decumana (Roxb.) Wedd] is a plant that is widely used as traditional medicine by Papuans as a pain reliever. The purpose of this study was to determine the total level of alkaloids in itchy leaf extract and to test the cytotoxic activity using the BSLT method. The research series began with the extraction stage with the maceration method using 96% ethanol, which tested the alkaloid level. The test was carried out using the gravimetric method and the cytotoxic test using the alkaloid level test results using the BSLT method on shrimp larvae (Artemia salina L). The results showed that itchy leaf extract contained a total alkaloid level of 6.46%. Cytotoxic testing using the BSLT method showed an LC50 of 54.33 ppm and was found to be toxic.