STRUCTURE-ANTIOXIDATIVE ACTIVITY RELATIONSHIPS IN BENZYLISOQUINOLINE ALKALOIDS

Abstract

The antioxidative properties of the aporphines boldine, glaucine and apomorphine, and of the benzyltetrahydroisoquinolines (f)-coclaurine and (f)-norarmepavine were compared in the brain homogenate autoxidation model. The I& values found lay in the 16-20 PM range for the aporphines and were 131.7 PM, and 79.3 ,UM for coclaurine and norarmepavine, respectively. These results indicate that the antioxidative capacity (AC) of these compounds is related to the presence of the biphenyl system rather than phenol groups. The non-phenolic glaucine inhibited the 2,2’-azobis-(2-amidinopropane)(AAP)-induced inactivation of lysozyme with an ICsO value of 12 PM, while the corresponding values for the phenolic coclaurine and norarmepavine were 10 and 20 ,UM, respectively. N-Methylation of glaucine to its quaternary ammonium reduced its protective effect by two-thirds. This result suggests that a benzylic hydrogen neighbouring a nitrogen lone electron pair may be the key to the protective effect of non-phenolic aporphines.