The antioxidant activity of 14 compounds (1−14) isolated from the ether and butanolic extracts ofthe aerial parts of Ophryosporus heptanthus has been assayed using a β-carotene bleaching methodand the DPPH technique. Compounds 1 and 13 showed the most potent antioxidant activity. Theirstructures have been established by spectroscopic techniques (mainly NMR). Compounds 7 and 12are new natural products, and their structures have been confirmed by chemical synthesis. Keywords: Diterpenes; polyphenols; antioxidant activity; Ophryosporus heptanthus