Structural characterization of prenylated compounds from Broussonetia kazinoki and their antiosteoclastogenic activity

An undescribed 1,3-diphenylpropane derivative, kazinol V and six undescribed prenylated flavonoids, broussonols F–H and broussonols K–M were isolated from the roots of Broussonetia kazinoki Siebold, together with 12 known compounds. This is the first report of the isolation and structure determination of broussonol I from a natural source. The chemical structure of the undescribed compounds was determined using conventional NMR and HRMS data. Absolute configurations were assigned using time-dependent density functional theory calculations and Electronic Circular Dichroism (ECD) spectroscopy. The isolated compounds were screened for their effects on RANKL-induced osteoclast formation using RAW264.7 cells. Among them, broussonols F, G, and K showed strong, dose-dependent antiosteoclastogenic activities. Broussonol K exhibited the most potent inhibitory activity and possessed bone resorption suppressive activity.