Abstract
Most of the species of the North American genus Encelia have been analysed for lipophilic flavonoids present as constituents of the resins secreted on the surfaces of leaves and stems. Thirty different flavonoids have been isolated and identified. The compounds included several new and unusual flavanones mainly based on pinocembrin, naringenin, and eriodictyol. The structural elucidation of these compounds by spectroscopic means is described. The flavonoid patterns are briefly discussed with regard to the systematics of Encelia.
