Ponderosa Pine Needle-Induced Abortion in Beef Cattle: Identification of Isocupressic Acid as the Principal Active Compound

Abstract

A crude acid fraction isolated from the needles of ponderosa pine (Pinus ponderosa Laws) induced abortions when fed to late-term pregnant beef cows. The major components identified in this abortifacient fraction were four long-chain fatty acids (palmitic, linoleic, oleic, and stearic acids), four abietane diterpene acids (isopimaric, dehydroabietic, abietic, and neoabietic acids), and two labdane diterpene acids (imbricataloic and isocupressic acids). From this crude acid fraction isocupressic acid was isolated and dosed by gavage to five pregnant cows starting on day 250 of pregnancy. Four of the five cows aborted calves when administered isocupressic acid at dosages between 99 and 152 mglkg (twice daily). At a lower dosage of 66 mglkg no abortion occurred. No abortifacient activity was observed after a mixture of the abietane diterpene acids was gavaged at dosages of 77 and 120 mg/kg (twice daily); but at higher dosages (238 and 255 mg/kg) these compounds were toxic, and two cows died. It was concluded that the primary abortifacient constituent in ponderosa pine is isocupressic acid and that a separate toxic syndrome may occur from ingestion of high levels of some abietane diterpene acids in pine needles.