Production and on-line acetylcholinesterase bioactivity profiling of chemical and biological degradation products of tacrine

The present paper describes a methodology for rapid assessment of chemical and biological degradation products of tacrine and their bioactivity for acetylcholinesterase (AChE). Analysis was achieved by utilizing liquid chromatography coupled to parallel high resolution mass spectrometry and an on-line continuous-flow AChE bioassay for biochemical detection. Key advantage of the strategy described involves the straightforward chemical production of large quantities of products of which many were the same as formed during the biological degradation by cytochromes P450 (CYPs). For this, chemical degradation of tacrine was evaluated under acidic, basic and oxidative conditions as well as elevated temperatures and light exposure. Chemical degradation products were only formed after 2 h under reflux with 3% hydrogen peroxide, where more than 50% of tacrine was converted to degradation products. Many of these products showed bioactivity. Mostly, mono-, di- or tri-oxygenated compounds were observed. This study demonstrated that the combination of chemical and biological degradation provides valuable information indicating that assessment of biological activity is important not only for biological degradation products, but also for chemical degradation products when formed. Furthermore, chemical degradation can be used to produce conveniently and in relatively large quantities clean mixtures of compounds that are also produced during metabolic incubations.