STRUCTURE-ANTIOXIDATIVE ACTIVITY RELATIONSHIPS IN BENZYLISOQUINOLINE ALKALOIDS

The antioxidative properties of the aporphines boldine, glaucine and a pomorphine, and of the benzyltetrahydroisoquinolines (+/-)-coclaurine and (+/-)-norarmepavine were compared in the brain homogenate autoxida tion model. The IC50 values found lay in the 16-20 mu M range for the aporphines and were 131.7 mu M, and 79.3 mu M for coclaurine and norar mepavine, respectively. These results indicate that the antioxidative capacity (AC) of these compounds is related to the presence of the bip henyl system rather than phenol groups. The non-phenolic glaucine inhi bited the 2,2'-azobis-(2-amidinopropane)(AAP)-induced inactivation of lysozyme with an IC50 value of 12 mu M, while the corresponding values for the phenolic coclaurine and norarmepavine were 10 and 20 mu M, re spectively. N-Methylation of glaucine to its quaternary ammonium reduc ed its protective effect by two-thirds. This result suggests that a be nzylic hydrogen neighbouring a nitrogen lone electron pair may be the key to the protective effect of non-phenolic aporphines.