In vitro antiplasmodial activity and chloroquine-potentiating action of three new isoquinoline alkaloid dimers isolated from Hernandia voyronii Jumelle.

Three new isoquinoline alkaloid dimers with pavine and benzyl-tetrahydroisoquinoline moieties have been isolated, by bioassay-guided fractionation, from an alkaloid extract of Hernandia (= Hazomalania) voyronii Jumelle. All had inherent antiplasmodial activity in vitro and two enhanced chloroquine effectiveness in vitro in a dose-dependent manner. Some structure requirements for the chloroquine-potentiating action were identified in the isoquinoline series. These results, if confirmed in vivo, would account for the traditional use of H. voyronii as an adjuvant to complement chloroquine action in Malagasy herbal remedies.