There are no uses for the strychnine tree (Strychnos nux-vomica L.) in modern medicine although it was widely used in medicine before World War II. The properties of Nux Vomica are those of the alkaloid strychnine. Herein we investigated phytochemically the aqueous methanolic extract of the S. Nux vomica and isolated five phenolic compounds; Kaempferol-7 Glucoside 1, 7 hydroxy Coumarin 2, Quercetin-3-Rhamnoside 3, Kaempferol 3-rutinoside 4, and Rutin 5.  At the same time, the cytotoxic activity of the extract was evaluated against different cancer cell lines.  The extract showed potential cytotoxic activity against human epidermoid larynx carcinoma cells, with IC₅₀ value 17.8 μg/mL.  It also exhibited promising cytotoxic activity against breast carcinoma cell line (MCF-7) with IC₅₀ 36.3 μg/mL.  Colon carcinoma cells were the least one affected by the extract as its IC₅₀ was 41.2 μg/mL.