ANTIMALARIAL ACTIVITY OF EXTRACTS AND FRACTIONS FROM BIDENS-PILOSA AND OTHER BIDENS SPECIES (ASTERACEAE) CORRELATED WITH THE PRESENCE OF ACETYLENE AND FLAVONOID COMPOUNDS

After interviewing natives and migrants from the Amazon region of Braz il about plants traditionally used for treatment of malaria fever and/ or liver disorders, we selected and identified 41 different species, i ncluding the native Bidens (Asteraceae). We have undertaken an antimal arial study of Bidens pilosa and other species of Bidens from abroad. The crude ethanol extracts (whole plant, leaves and roots) and the chl oroform and butanol fractions from B. pilosa at concentrations of 50 m u g/ml caused up to 90% inhibition of Plasmodium falciparum growth in vitro. In vivo the fractions caused partial reduction of Plasmodium be rghei parasitemia in mice. The ethanol extracts from nine different Bi dens species collected outside Brazil were tested, and seven inhibited parasite growth in vitro by 65-91%. As B. pilosa appears to be a prom ising antimalarial agent, we further characterized the substances resp onsible for such activity. HPLC analysis using a photo diode-array det ector showed phenyl acetylene and flavonoids in the ethanol extract fr om the leaves and roots. The chloroform fractions from the roots, whic h caused 86% inhibition of parasite growth in vitro, contained a major component identified as 1-phenyl-1,3-diyn-5-en-7-ol-acetate. The asso ciation of antimalarial activity and the presence of acetylene compoun ds is discussed. In summary, all species of Bidens which had aliphatic acetylenes (6-14 each) were also very active: whereas extracts of B. parviflora a and of B. bitternata with none or the three acetylenes, r espectively as reported in literature, were inactive or had a borderli ne activity in vitro. (C) 1997 Elsevier Science Ireland Ltd.