Cytotoxic and antimalarial bisbenzylisoquinoline alkaloids from Cyclea barbata.

An alkaloid extract derived from the roots of Cyclea barbata demonstrated cytotoxic and antimalarial activities, and five bisbenzylisoquinoline alkaloids, (+)-tetrandrine [1], (-)-limacine [2], (+)-thalrugosine [3], (+)-homoaromoline [4], and (-)-cycleapeltine [5], were isolated as the active principles. The complete and unambiguous assignments of the 1H- and 13C-nmr data of these substances were made by 1D and 2D nmr techniques (COSY, phase-sensitive ROESY, HETCOR, and FLOCK).