Various plant species termed chloroquine (CQ) adjuvants, have been used to supplement CQ effectiveness in Madagascar. As guided by bioassay to reverse the CQ-resistant strain FCM29 of Plasmodium falciparum, two known bisbenzylisoquinoline alkaloids, three novel isoquinoline dimers and five indole alkaloids, of which three are new, were isolated from four plant species. Some structural requirements for drug resistance reversal were identified. © 1994 IUPAC