Spectral characterisation and antiplasmodial activity of bisbenzylisoquinolines from Isolona ghesquiereina

From stem barks of Isolona guesquiereina three known bisbenzylisoquinolines were isolated and identified as (-)-curine, chondrofoline and isochondoden drine. Structures were established mainly on the basis of comparison of the ir physical and spectral data with published data for them and their methyl ated derivatives. Cleavage with sodium in liquid ammonia was necessary to u nambiguously determine the stereochemistry of (-)-curine and subsequently e stablish its stereochemical link with chondrofoline, erroneously assigned a s 7-O-methyl-(+)-curine. Complete and unambiguous H-1-, N-15- and C-13-NMR assignments of the three alkaloids were made by means of 2D-NMR techniques namely, COSY, HMQC, gs-HMQC, HMBC and NOESY. (-)-Curine, isochondrodendrine and their methylated derivatives were shown to exhibit strong in vitro ant iplasmodial activity and in vivo activity was also observed for (-)-curine.