A kaempferol glycoside that selectively inhibits RSK2 with an IC50 value of 89 nM (Ki = 1 μM) without interfering with upstream activators of RSK, including ERK, MEK, EGFR, and PKC; inhibits the proliferation of MCF-7 breast cancer cells at 100 μM and attenuates angiotensin II-induced cell proliferation at 30 μM.