Chinquapinic Acid: A Novel Hydrolyzable Tannin Isolated from Chrysolepis Sempervirens

Scanning electron microscopy showed that the undersides of the leaves of Chrysolepis sempervirens (Fagaceae) are covered with crystalline epidermal powder. An examination of the chemical composition of the epidermal powder has led to the isolation and characterization of a new C-glycosidic, hydrolyzable tannin, chinquapinic acid (3), in addition to two known tannins, vescalagin (1) and castalagin (2). The structure and stereochemical properties of (3) were established by relying on analogies to castalagin and vescalagin, along with evidence gained from NMR experiments and conversion to vescalagin. These tannins have cytotoxic activities and are the first examples of this class of compound to be exuded from the plant surface.