Determination of N-acetyldopamine by liquid chromatography with electrochemical detection

Simultaneous quantification methods and sample preparation methods for five typical biogenic amines (5-hydroxytryptamine, dopamine, epinephrine, norepinephrine, and octopamine), one precursor (tyramine), and three metabolites (N-acetyldopamine, N-acetyloctopamine, and synephrine) using HPLC with an electrochemical detector were developed. These methods were applied to investigating the distribution of these amine derivatives in the central nervous system of last instar of Spodoptera litura. In the central nervous system, all amines listed above were detected; among those, N-acetyldopamine and N-acetyloctopamine existed at relatively high levels rather than their free-amines. Chlordimeform, a potent antifeedant, caused an increase in N-acetyldopamine levels in cerebral and suboesophageal ganglia and a decrease in 5-hydroxytryptamine and N-acetyloctopamine levels in the cerebral, suboesophageal, and thoracic ganglia. On the other hand, aristolochic acid I, a newly found antifeedant from Aristolochia albida, did not cause any statistically significant change in any amine levels, except for dopamine and 5-hydroxytryptamine in suboesophageal ganglia and tyramine in thoracic ganglia. From these results, it has been suggested that chlordimeform and aristolochic acid I each had a different mode of antifeedant activity against S. litura.