A survey of tremetone, dehydrotremetone, and structurally related compounds in Isocoma spp. (goldenbush) in the southwestern United States.

Isocoma pluriflora, a plant prevalent on land used for livestock production and native to Arizona, New Mexico, West Texas, and Northern Mexico, is poisonous and causes trembles in livestock. Tremetone and dehydrotremetone have been suggested as the toxic compounds in I. pluriflora. In this study several different Isocoma spp., including I. pluriflora, I. tenuisecta, I. azteca, I. acradenia, and I. rusbyi, that are native to land used for grazing livestock in the southwestern United States were analyzed by high performance liquid chromatography (HPLC) for tremetone, dehydrotremetone, and other structurally related compounds. This is the first report of tremetone, dehydrotremetone, and 3-oxyangeloyltremetone in I. tenuisecta, I. azteca, I. acradenia, I. rusbyi, and several other Isocoma spp. In addition, this is the first report of 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone and 7-isopentenyloxycoumarin in Isocoma spp.