Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2005
Publication Date: 4/14/2005
Citation: Lee, S.T., Molyneux, R.J., Panter, K.E., Chang, C.T., Gardner, D.R., Pfister, J.A., Garrossian, M. 2005. Ammodendrine and n-methylammodendrine enantiomers: isolation, optical rotation, and toxicity. Journal of Natural Products.
Interpretive Summary: Ingestion of Lupinus formosus by pregnant cows at specific gestational periods can result in calves with cleft palate and front limb contractures, commonly known as crooked calf disease. Ammodendrine, a piperidine alkaloid, found in L. formosus is a reported teratogen. L. formosus was collected at different sites in California. Ammodendrine was a major alkaloid in both plant collections. Ammodendrine has a chiral center indicating that it could be present in enantiomeric mixtures in the plants. By reacting the ammodendrine isolated from these plant collections with a pure L-alanine based enantiomer we obtained alanine-ammodendrine based diasteriomers which were separated and isolated by HPLC. Pure D- and L-ammodendrine enantiomers were obtained by an Edman degradation procedure. D- and L-N-Methylammodendrine were synthesized. The optical rotation of the values of D- and L-ammodendrine and D- and L-N-methylammodendrine were established. A mouse bioassay was used to determine the difference in toxicity between D and L ammodendrine and D and L N-methyl ammodendrine.
Technical Abstract: Ammodendrine (1) was found to occur as a mixture of enantiomers in two different collections of plants identified as Lupinus formosus. The ammodendrine fraction was reacted in a peptide coupling reaction with Fmoc-L-Ala-OH to give diastereomers which were separated by preparative HPLC. The pure D and L ammodendrine enantiomers were then obtained by Edman degradation. Optical rotation measurements revealed that the D and L enantiomers had optical rotations of [']24D +5.4' and '5.7', respectively. D and L N-methylammodendrine enantiomers were synthesized from the corresponding ammodendrine enantiomers, and their optical rotations established as [']23D +62.4° and '59.0°, respectively. A mouse bioassay was used to determine the difference in toxicity between these two pairs of naturally occurring enantiomers. The LD50 of (+)-D-ammodendrine in mice was determined to be 94.1'6.8 mg/kg and that of (-)-L-ammodendrine as 115.0'7.0 mg/kg. The LD50 of (+)-D-N-methyl ammodendrine in mice was estimated to be 56.3 mg/kg while that of (-)-L-N-methyl ammodendrine was determined to be 63.4'4.7 mg/kg. These results establish the rotation values for pure ammodendrine and N-methylammodendrine and indicate that there is little difference in acute toxicity between the respective enantiomers.