1. (±)-Praeruptorin A could exhibit its anti-osteoclastogenic activity by inhibiting p38/Akt-c-Fos-NFATc1 signaling and PLCγ-independent Ca(2+) oscillation 2. Praeruptorin A has the potential to inhibit migration/fusion of preosteoclasts in vitro and bone erosion in vivo by targeting calmodulin and inhibiting the Ca(2+)/calmodulin-CaMKIV-CREB-NFATc1 and/or Ca(2+)/calmodulin-calcineurin-NFATc1 signaling axis. 3. Praeruptorin A and praeruptorin C can significantly upregulate multidrug resistance-associated protein 2 expression via the constitutive androstane receptor-mediated pathway in vitro, and this should be taken as an herb-drug interaction.