Dihydrochalcones from Piper longicaudatum

Bioactivity-guided fractionation of an ethanolic extract of the leaves and twigs of Piper longicaudatum Trelease & Yunker (Piperaceae) resulted in the isolation of one new (1) and three known (2-4) dihydrochalcones. The known compounds are: 2',6'-dihydroxy-4'-methoxydihydrochalcone (2), 2',6',4-trihydroxy-4'-methoxydihydrochalcone (asebogenin) (3), and 2'-hydroxy-4'methoxy-2'[1-hydroxy-1-methylethyl]-2 " ,3 " -dihydro-furano[4 " ,5 " :5',6 "]-3 "-[2-hydroxy-5-methoxycarbonylphenyl] dihydrochalcone (piperaduncin B) (4). The new compound is 2'-hydroxy-4'-methoxy-2 "-[2-hydroxy-5-methoxycarbonylphenyl]-furano[4 " ,5 ": 5',6']-dihydrochalcone (longicaudatin) (1), Compounds 1-4 were tested for antibacterial activity against S. aureus and methicillin-resistant S. aureus (MRSA); only compound 3 showed inhibitory activity (IC50 of 10 and 4.5 mug/ml, respectively).