Poisonous Piperidine Plants and the Biodiversity of Norditerpenoid Alkaloids for Leads in Drug Discovery: Experimental Aspects

There are famous examples of simple (e.g., hemlock, Conium maculatum L.) and complex (e.g., opium poppy, Papaver somniferum L., Papaveraceae) piperidine-alkaloid-containing plants. Many of these are highly poisonous, whilst pepper is well-known gastronomically, and several substituted piperidine alkaloids are therapeutically beneficial as a function of dose and mode of action. This review covers the taxonomy of the genera Aconitum, Delphinium, and the controversial Consolida. As part of studying the biodiversity of norditerpenoid alkaloids (NDAS), the majority of which possess an N-ethyl group, we also quantified the fragment occurrence count in the SciFinder database for NDA skeletons. The wide range of NDA biodiversity is also captured in a review of over 100 recently reported isolated alkaloids. Ring A substitution at position 1 is important to determine the NDA skeleton conformation. In this overview of naturally occurring highly oxygenated NDAs from traditional Aconitum and Delphinium plants, consideration is given to functional effect and to real functional evidence. Their high potential biological activity makes them useful candidate molecules for further investigation as lead compounds in the development of selective drugs.

An agent-based model of cattle grazing toxic Geyer's larkspur

By killing cattle and otherwise complicating management, the many species of larkspur (Delphinium spp.) present a serious, intractable, and complex challenge to livestock grazing management in the western United States. Among the many obstacles to improving our understanding of cattle-larkspur dynamics has been the difficulty of testing different grazing management strategies in the field, as the risk of dead animals is too great. Agent-based models (ABMs) provide an effective method of testing alternate management strategies without risk to livestock. ABMs are especially useful for modeling complex systems such as livestock grazing management, and allow for realistic bottom-up encoding of cattle behavior. Here, we introduce a spatially-explicit, behavior-based ABM of cattle grazing in a pasture with a dangerous amount of Geyer's larkspur (D. geyeri). This model tests the role of herd cohesion and stocking density in larkspur intake, finds that both are key drivers of larkspur-induced toxicosis, and indicates that alteration of these factors within realistic bounds can mitigate risk. Crucially, the model points to herd cohesion, which has received little attention in the discipline, as playing an important role in lethal acute toxicosis. As the first ABM to model grazing behavior at realistic scales, this study also demonstrates the tremendous potential of ABMs to illuminate grazing management dynamics, including fundamental aspects of livestock behavior amidst ecological heterogeneity.

Development of a PCR-Based Method for Detection of Delphinium Species in Poisoned Cattle

Toxic plants such as Delphinium spp. (i.e., larkspur) are a significant cause of livestock losses worldwide. Correctly determining the causative agent responsible for the death of an animal, whether by disease, poisonous plant, or other means, is critical in developing strategies to prevent future losses. The objective of this study was to develop an alternative diagnostic tool to microscopy and analytical chemistry to determine whether a particular poisonous plant was ingested. Polymerase chain reaction (PCR) is a tool that may allow detection of the genetic material from a specific plant within a complex matrix such as rumen contents. A pair of oligonucleotide primers specific to Delphinium spp. (i.e., larkspur) was developed; using these primers, a PCR product was detected in samples from an in vivo, in vitro, and in vivo/in vitro coupled digestion of Delphinium occidentale. Lastly, larkspur was detected in a matrix of ruminal material where the amount of larkspur was far less than what one would expect to find in the rumen contents of a poisoned animal. The PCR-based technique holds promise to diagnose larkspur and perhaps other toxic plant caused losses.

The toxicity and kinetics of larkspur alkaloid, methyllycaconitine, in mice

Larkspur poisoning sporadically kills from 5 to 15% of the cattle on North American mountain rangelands. Of the 40 different diterpenoid larkspur alkaloids, the one that is thought to be responsible for much of the toxicity has been identified as methyllycaconitine (MLA). Little is known of MLA toxicokinetics or excretion. The purpose of this study was to further characterize the clinical effects of MLA toxicity in mice and determine the toxicokinetics of MLA excretion. Eight groups of mice were dosed intravenously with 2.0 mg/kg of BW of MLA, killed, and necropsied at 0, 1, 2, 5,10,15, 30, and 60 min after injection. Treated animals were reluctant to move, trembled, and developed dyspnea, muscular twitches, and convulsions. Within several minutes, the clinical signs abated and behavior slowly returned to normal over approximately 20 min. At necropsy serum, brain, liver, kidney, and skeletal muscle were collected and frozen. Blood and tissues were extracted and analyzed for MLA with HPLC and electron spray mass spectrometry. Blood MLA elimination followed a normal biphasic redistribution and excretion pattern (r = 0.99) with a K of elimination of 0.0376 and half-life of 18.4 min. Other tissues had similar clearance rates. These data indicate the MLA is rapidly distributed and excreted. In mice, the clinical effects of poisoning seem to affect the central nervous system, causing dyspnea and "explosive" muscular twitches and convulsions. Because livestock commonly eat larkspur at subclinical doses, they are likely to have larkspur alkaloids in many tissues. These results suggest that animals exposed to larkspur should rapidly excrete MLA (within several hours) and that the residues in animal tissues are not likely to be a problem if animals are given several days to allow toxin clearance.