| Abstract
| - 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 larkspurDelphinium nuttallianum. The structures of the individual alkaloids were determined by 1H and 13CNMR spectroscopy and HRMS. These alkaloids are structurally related to the neurotoxic alkaloidmethyllycaconitine (4) and may be important in establishing the toxicity of low larkspurs to cattle. Amouse bioassay was used to measure the LD50 values for two of the new alkaloids (1 and 2), as sufficientquantities of 3 were not available for toxicity testing. A structurally related alkaloid, geyerline (7), wasisolated from D. geyeri in sufficient quantities for toxicity testing. The toxicities of 1, 2, and 7 were foundto be comparable to that of 4, with calculated LD50 values in mice of 5.7, 3.3, and 6.2 mg/kg, respectively.
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