Five new diprenylated flavonols from the leaves of Broussonetia kazinoki

Five new diprenylated flavonols, broussonol A (1), broussonol B (2), broussonol C (3), broussonol D (4), and broussonol E (5), along with two known compounds, were isolated from an ethanolic extract of the leaves of Broussonetia kazinoki. Their structures were elucidated by chemical and spectral methods. Cytotoxic activities were evaluated against several different cell lines.