The growing resistance to anticancer agents has turned medical science and pharmacology towards findingnew compounds with these characteristics; in this area the natural products have great relevance, sincemany of these have anticancer activity. Flavonoids as secondary metabolites have reported anti-tumoractivity and can become important source for cancer treatment; why search isolate flavonoids Browneaariza Brenth to evaluate their anticancer activity. The Phytochemical analysis of leaves of Brownea arizaBrenth. (Caesalpiniaceae) let isolate a flavonol identified as (1), and a glycoside flavonol described asQuercitrin (2). The structures are determined by spectroscopic techniques: UV-Vis with shift reagents; 1D and 2D NMR (1H, 13C, COSY, DEPT, HMBC; HMQC), and mass spectrometry. It evaluates thecytotoxic activity in VERO cell (ATCC: CCL-81) and anticancer activity in Myeloma Murino SP2/0-Ag14(ATCC: CRL-1581), doing count the number of viable cells by graduation with tripan blue, obtaining aconcentration cytotoxic average (1) of 300 μg/mL and not determined to (2) in concentrations of work;anticancer activity for (1) has a median effective concentration of 150 μg /mL and not given to (2) inconcentrations of work.