Three new toxic norditerpenoid alkaloids from the low larkspur Delphinium nuttallianum.
Three new N-(methylsuccinimido)anthranoyllycoctonine norditerpenoids, given the names bearline (1), 14-acetylbearline (2), and 16-deacetylgeyerline (3), were isolated from the extract of the low larkspur Delphinium nuttallianum. The structures of the individual alkaloids were determined by (1)H and (13)C NMR spectroscopy and HRMS. These alkaloids are structurally related to the neurotoxic alkaloid methyllycaconitine (4) and may be important in establishing the toxicity of low larkspurs to cattle. A mouse bioassay was used to measure the LD(50) values for two of the new alkaloids (1 and 2), as sufficient quantities of 3 were not available for toxicity testing. A structurally related alkaloid, geyerline (7), was isolated from D. geyeri in sufficient quantities for toxicity testing. The toxicities of 1, 2, and 7 were found to be comparable to that of 4, with calculated LD(50) values in mice of 5.7, 3.3, and 6.2 mg/kg, respectively.
Gardner
D R
DR
Poisonous Plant Research Laboratory, Agricultural Research Service, United States Department of Agriculture, 1150 E. 1400 N., Logan, Utah 84341, USA. gardnerd@cc.usu.edu
Manners
G D
GD
Panter
K E
KE
Lee
S T
ST
Pfister
J A
JA
D000157:Aconitine / Q000031:analogs & derivatives / Q000737:chemistry / Q000302:isolation & purification; D000470:Alkaloids / Q000737:chemistry / Q000302:isolation & purification*; D000818:Animals; D001681:Biological Assay; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification*; D008401:Gas Chromatography-Mass Spectrometry; D007928:Lethal Dose 50; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051379:Mice; D018515:Plant Leaves / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D010947:Plants, Toxic / Q000737:chemistry*; D014589:Utah
C414608:14-acetylbearline; C414607:16-deacetylgeyerline; D000470:Alkaloids; D004224:Diterpenes; C414606:bearline; C054634:methyllycaconitine; D000157:Aconitine