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United States Department of Agriculture

Agricultural Research Service

Title: Relative Toxicities and Neuromuscular Nicotinic Receptor Agonistic Potencies of Anabasine Enantiomers and Anabaseine

Authors
item Lee, Stephen
item Wildeboer, Kristin - USU
item Panter, Kip
item Kem, William - USU
item Gardner, Dale
item Molyneux, Russell
item Chang, Cheng-Wei - USU
item Soti, Ferenc - U OF FLORIDA
item Pfister, James

Submitted to: Neurotoxicology and Teratology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2005
Publication Date: February 20, 2006
Citation: Lee, S.T., Wildeboer, K., Panter, K.E., Kem, W., Gardner, D.R., Molyneux, R.J., Chang, C.T., Soti, F., Pfister, J.A. 2006. Relative toxicities and neuromuscular nicotinic receptor agonistic potencies of anabasine enantiomers and anabaseine. Neurotoxicology and Teratology.

Interpretive Summary: Anabasine occuring as a racemic mixture of enantiomers in wild tree tobacco (Nicotinana glauca) and anabaseine occuring in certain animal venoms are toxins. Anabasine is similar in structure to anabaseine but lacks the imine double bond of anabaseine. We separated the enantiomers of anabasine by reaction of the racemic N. glauca natural product with 9-fluorenylmethoxycarbonyl-L-alanine (Fmoc-L-Ala-OH) to give diastereomers, which were separated by preparative reversed phase HPLC. The S- and R-anabasine enantiomer fractions were then obtained by Edman degradation. A mouse bioassay was used to determine the relative toxicity of S- and R-enriched anabasine enantiomers. The intravenous LD50 of the (+)-R-anabasine rich fraction was 11.0±1 mg/kg and that of the (-)-S-anabasine-rich fraction was 16.0±1 mg/kg. The LD50 of anabaseine was also determined to be 0.58±0.05 mg/kg. Anabaseine was significantly more lethal than S-anabasine (27-fold) and R-anabasine (18-fold). The relative agonistic potencies of the three alkaloids on human fetal nicotinic neuromuscular receptors were of the same rank order: anabaseine >> S-anabasine > R-anabasine.

Technical Abstract: Anabasine occurring in wild tree tobacco (Nicotinana glauca) and anabaseine occurring in certain animal venoms are nicotinic receptor agonist toxins. Anabasine lacks the imine double bond of anabaseine; the two possible enantiomers of anabasine occur in N. glauca. A comparision of the relative potencies of S- and R-anabasine has not been previously reported. We separated the enantiomers of anabasine by reaction of the racemic N. glauca natural product with 9-fluorenylmethoxycarbonyl-L-alanine (Fmoc-L-Ala-OH) to give diastereomers, which were separated by preparative reversed phase HPLC. The S- and R-anabasine enantiomer fractions were then obtained by Edman degradation. A mouse bioassay was used to determine the relative lethalities of S- and R-enriched anabasine enantiomers. The intravenous LD50 of the (+)-R-anabasine rich fraction was 11±1.0 mg/kg and that of the (-)-S-anabasine-rich fraction was 16±1.0 mg/kg. The LD50 of anabaseine was 0.58±0.05 mg/kg. Anabaseine was significantly more toxic in the mouse bioassay than S-anabasine (27-fold) and R-anabasine (18-fold). The relative agonistic potencies of the three alkaloids on human fetal nicotinic neuromuscular receptors were of the same rank order: anabaseine >> S-anabasine > R-anabasine.

Last Modified: 7/28/2014