Isolation and characterization of glucocapparin inIsomeris arborea nutt.

Isomeris arborea (Capparaceae), is the only woody caper endemic to southern California and northern Baja. Methylglucosinolate, also known as glucocapparin, was the only glucosinolate found inI. arborea organs by paper chromatography of the thiourea derivatives and was quantitatively determined by gas chromatography by hydrolytic products. The concentration of glucocapparin ranged from an average of 4.6 mg/g wet weight in mature leaves to 5.2 mg/g wet weight in immature leaves. Buds averaged 6.2 mg/g wet weight and capsule walls 1.8 mg/g wet weight. Seeds contained an average of 14.3 mg/g wet weight of glucocapparin. Glucocapparin concentration was found to vary significantly among the mature leaves of individuals within a single population. This compound is known to be deleterious to nonadapted herbivores and may be implicated in the chemical defense mechanism ofI. arborea.