Bioactive secondary metabolites from Boesenbergia pandurata of Myanmar and their preferential cytotoxicity against human pancreatic cancer PANC-1 cell line in nutrient-deprived medium

The chloroform extract of rhizomes of Boesenbergia pandurata demonstrated marked preferential cytotoxicity against human pancreatic PANC-1 cancer cells in nutrient-deprived medium. Bioactivity-directed investigation of this extract yielded four new secondary metabolites, geranyl-2,4-dihydroxy-6-phenethylbenzoate (1), 2',4'-dihydroxy-3'-(1 ''-geranyl)-6'-methoxychalcone (2), (1'R,2'S,6'R)-2-hydroxyisopanduratin A (3), and (2R)-8-geranylpinostrobin (4), and twenty known compounds (5-24). Among the known compounds, (2S)-6-geranylpinostrobin (5), (+/-)-6-methoxypanduratin A (6), and (2S)-7,8-dihydro-5-hydroxy-2-methyl-2-(4 ''-methyl-3 ''-pentenyl)-8-phenyl-2H,6H-benzo[1,2-b:5,4-b']dipyran-6-one (7) were isolated for the first time from a natural source. The structures of these compounds were elucidated using extensive spectroscopic techniques including CD measurements. All the isolated compounds showed varying degrees of in vitro preferential cytotoxicity against PANC-1 cells. Nicolaioidesin B (11) and panduratin A (17) were most potent, each showing a PC100 at 2.5 mu M.