Gibbilimbols A-D, cytotoxic and antibacterial alkenylphenols from Piper gibbilimbum

Fractionation of the petroleum ether extract from the leaves of Piper gibbilimbum collected in Papua New Guinea afforded four new alkenylphenols, gibbilimbols A-D (1-4). The structures of the isolates were elucidated by spectroscopic methods, mainly 1D- and 2D-NMR spectroscopy. Gibbilimbols A-D were found to he toxic to brine shrimp with an LC50 of approximately 5 mu g/mL. Gibbilimbols A-D were further found to be cytotoxic toward KB nasopharyngal carcinoma cells (ED50 7.8-2.1 mu g/mL). All isolates also showed antibacterial activity toward Staphylococcus epidermidis and Bacillus cereus.