In Vitro Antimalarial Activity and Chloroquine Potentiating Action of Two Bisbenzylisoquinoline Enantiomer Alkaloids Isolated from Strychnopsis thouarsii and Spirospermum penduliflorum - Ratsimamanga-Urverg, S; Rasoanaivo, P; Ramiaramanana, L; Milijaona, R; Rafatro, H; Verdier, F; Rakoto-Ratsimamanga, A; Le Bras, J (Planta Medica, 1992)