Development of enzyme-linked immunosorbent assays for toxic larkspur (Delphinium spp.) alkaloids

Larkspur (Delphinium spp.) poisons thousands of cattle on western rangelands each year. Because poisoning does not cause specific lesions, and poisoned animals are rarely found before they die, definitively identifying poisoned animals is difficult. Additionally, toxin concentrations in larkspur plants vary with environment, plant, and location. Rapid, sensitive, and specific diagnostic techniques are needed to identify poisoned animals and to determine when and what plants are likely to poison livestock. In this study, three competitive inhibition enzyme-linked immunosorbent assays (CI-ELISA) for toxic larkspur alkaloids were developed. One assay is class-specific toward the N-(methylsuccinimido)anthranoyllycoctonine (MSAL) alkaloids, and two assays are specific for individual alkaloids. The assay with the lowest limit of detection had an I(50) of 191 pg with a limit of detection of 30.5 pg for methyllycaconitine. Spike and recovery studies using bovine blood and brain tissue ranged from 52 to 89%. These findings suggest that with additional development these techniques are likely to be excellent tools for diagnosing poisoned animals and identifying highly toxic plants.