IADR Abstract Archives
Degradation and Ethanolic Transesterification of Arecoline, a Betel Nut Toxin
Objectives: The objectives of this study were to determine if arecoline is degraded to arecaidine (less toxic alkaloid) by human liver, and to ascertain if arecoline interacts with alcohol.
Methods: An ion-pair HPLC assay with ultraviolet-detection (UV) was developed to measure arecoline and arecaidine following simulated physiological experiments. Increasing concentrations of arecoline (8 μM to 2000 μM) were incubated in phosphate buffer (pH 7.4) at 37°C for 90 minutes in the presence of fresh or heat-inactivated human liver microsomes (HLM). Possible formation of ethyl arecoline (transesterification product) was detected in similar metabolic incubations with or without ethanol.
Results: In comparison to control, arecoline was rapidly degraded to arecaidine by HLM, a reaction dependent on time, substrate concentration, and HLM concentration. Total depletion of arecoline occurred within 90 minutes, with an apparent half-life 6.5±0.16 min. Enzymatic formation of arecaidine was linear and non-saturable under the tested conditions. Arecoline was converted to an ethyl-ester derivative, we surmise, by HLM only when co-incubated with ethanol.
Conclusions: For the first time, our studies demonstrate that arecoline is rapidly metabolized to arecaidine by human liver. In addition, our work suggests that arecoline possibly interacts with ethanol, forming a novel transesterification product. Future studies will focus on identifying the specific enzyme(s) responsible for arecoline detoxification, and will elucidate the toxicological profile of the peculiar metabolite ethyl arecoline in comparison to its precursor arecoline – a known oral toxin.
Methods: An ion-pair HPLC assay with ultraviolet-detection (UV) was developed to measure arecoline and arecaidine following simulated physiological experiments. Increasing concentrations of arecoline (8 μM to 2000 μM) were incubated in phosphate buffer (pH 7.4) at 37°C for 90 minutes in the presence of fresh or heat-inactivated human liver microsomes (HLM). Possible formation of ethyl arecoline (transesterification product) was detected in similar metabolic incubations with or without ethanol.
Results: In comparison to control, arecoline was rapidly degraded to arecaidine by HLM, a reaction dependent on time, substrate concentration, and HLM concentration. Total depletion of arecoline occurred within 90 minutes, with an apparent half-life 6.5±0.16 min. Enzymatic formation of arecaidine was linear and non-saturable under the tested conditions. Arecoline was converted to an ethyl-ester derivative, we surmise, by HLM only when co-incubated with ethanol.
Conclusions: For the first time, our studies demonstrate that arecoline is rapidly metabolized to arecaidine by human liver. In addition, our work suggests that arecoline possibly interacts with ethanol, forming a novel transesterification product. Future studies will focus on identifying the specific enzyme(s) responsible for arecoline detoxification, and will elucidate the toxicological profile of the peculiar metabolite ethyl arecoline in comparison to its precursor arecoline – a known oral toxin.