Seven phenolic compounds, scopoletin (1), caffeic acid methyl ester (2), apigenin 7-O-${alpha}$-L-rhamnosyl-(1${ ightarrow}$6)-O-${alpha}$-D-glucoside (3), isorhamnetin 7-O-${alpha}$-D-glucoside (4), isorhamnetin 3-O-${alpha}$-D-glucoside (5), luteolin (6), and quercetin 3-methyl ether (7) were isolated from the methanol extract of the flowers of S. excelsus. Their structures were established by chemical and spectroscopic methods. The isolated compounds were tested for their cytotoxicity against four human cancer cell lines in vitro using a SRB method. The compounds 4 and 7 showed moderate cytotoxicity with ED$_{50}$ values ranging from 1.59 to 13.14${mu}$g/ml.