Crotalaria medicaginea associated with horse deaths in northern Australia: new pyrrolizidine alkaloids.

The study investigates horse deaths in northern Australia linked to consumption of a plant known as Crotalaria medicaginea containing previously uncharacterized pyrrolizidine alkaloids.

Summary of Research

• The research explores the connection between horse poisoning in the central-west Queensland grazing regions and the Crotalaria medicaginea plant, which led to the death of over 35 horses due to hepatotoxicosis in 2010.
• Horse liver pathology suggested the cause of death to be pyrrolizidine alkaloidosis – a type of poisoning caused by the consumption of certain types of plants containing pyrrolizidine alkaloids.
• The researchers isolated two previously unidentified pyrrolizidine alkaloids from C. medicaginea plants gathered from the pastures where the affected horses died.

Findings

• The first alkaloid identified in the plant was 1β,2β-epoxy-7β-hydroxy-1α-methoxymethyl-8α-pyrrolizidine, found through mass spectrometric and NMR analyses. This alkaloid, though similar to other alkaloids earlier isolated from C. medicaginea, was not identified as a cause for hepatotoxicity in horses.
• The second alkaloid was a new macrocyclic diester of otonecine, which the researchers named cromedine. The constitution of this macrocyclic diester was unambiguously assigned using 2D NMR techniques.
• The C. medicaginea specimens related to this investigation were not part of the three recognized Australian varieties (C. medicaginea var. neglecta, C. medicaginea var. medicaginea, and C. medicaginea var. linearis), but appeared to be a local variant. The researchers referred to this variant as C. medicaginea (chemotype cromedine).

Implications of Research

• This research has crucial implications for the horse farming community in regions where the C. medicaginea (chemotype cromedine) variety is found.
• The identification of cromedine, a potentially deadly alkaloid in the local variant of C. medicaginea, can inform preventative measures to safeguard horses from further harm.
• Further research is required to assess the impact of both identified alkaloids, as well as potential compound interactions on the hepatotoxicity in horses.