Humupulusones A and B, Two Skeletally Novel Acylphloroglucinol Derivatives from <i>Humulus lupulus</i>

Two novel acylphloroglucinol derivatives, humupulusones A and B ( 1 and 2 ), were isolated from Humulus lupulus . Compound 1, a pair of enantiomers ( 1a / 1b ), is the first acylphloroglucinol derivative with a bicyclo[2.2.2] carbon skeleton possessing a novel 5/6/6/5/5 ring system. Humupulusone B ( 2 ), a pair of hemiacetal tautomers, features a highly rearranged 5/6/5-fused tricyclic scaffold. Moreover, 1a and 2 exhibited significant inhibitory effects on LPS-induced NO production in BV-2 cells with IC 50 values of 13.55 and 16.09 μM, respectively.