Cockleburs are a herbaceous annual found in the U.S. along the shores of streams and ponds and in low-lying areas of farm fields. In its seedling stage it contains a hyperglycemic glycoside named carboxyatractyloside that can be deadly to livestock.
Cockleburs tend to grow in areas that are waterlogged much
of the year, but dry during the summer. They have a fruit capsule containing
two seeds. Only one seed germinates the first year. Germination is delayed
in the second seed until the following year. Cocklebur seedlings are high
in carboxyatractyloside until the emergence of their first true leaves
after which toxicity is lost. Carboxyatractyloside is a plant growth inhibitor.
It has been hypothesized that carboxyatractyloside functions in a germinating
cocklebur seed to keep the other seed in the fruit capsule dormant the
same year.
Carboxyatractyloside causes hypoglycemia
in animals that consume it probably because it causes uncoupling of oxidative
phosphorylation. Experimentally, phenylbutazone (BUTE) has been shown to
reduce its toxicity by inducing synthesis of a non-cytochrome P450-dependent
detoxification enzyme.
Rooting pigs are very susceptible to poisoning from cocklebur seedlings. Symptoms include
Prior to death, animal becomes severely hypoglycemic with
blood glucose levels dropping to 16mg/100ml. Increased vascular permeability
leads to gross lessions of the gall bladder and peritoneal cavity and to
liver necrosis.
This series of web pages was created by an undergraduate student at Cornell University for the AS625 class. All comments and suggestions are welcome.
WARNING: These web pages are only meant to be informative. Neither Cornell University nor the author of this site endorse or recommend the use of these plants.
