Activity-guided isolation of antiplasmodial dihydrochalcones and flavanones from Piper hostmannianum var. berbicense

The bioassay-guided purification of an n-hexane extract from the leaves of Piper hostmannianum var. berbicense led to the isolation of four monoterpene or prenyl-substituted dihydrochalcones (1a, 1b, 2, 3) as well as the known compounds 2 ',6 '-dihydroxy-4 '-methoxydihydrochalcone (4), linderatone (5), strobopinin (6), adunctin E (7) and (-)-methyllinderatin (8). Their structures were established on the basis of NMR and X-ray analysis. (-)-Methyllinderatin, linderatone and 2 ',6 '-dihydroxy-4 '-methoxydihydrochalcone exhibited the most potent antiplasmodial activity with IC50 values of 5.64, 10.33 and 12.69 mu M, respectively against both chloroquine-sensitive and resistant strains of Plasmodium falciparum (F32, FcBl). The activity of (-)-methyllinderatin was confirmed in vivo against Plasmodium vinckei petteri in mice (80% of reduction of parasitemia) at a dose of 20 mg/kg/day. (c) 2007 Elsevier Ltd. All rights reserved.