n this study, we identified three novel antioxidants, subamolide C (1), subamolide E (2) and isokotomolide A (3) from the constitutes of Cinnamomum subavenium and Cinnamomum kotoense. The radical scavenging properties and two more antioxidant activities of the three compounds were examined. All compounds presented effective 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging capabilities compared with vitamin C; the metal chelating power evaluated to ethylene diamine tetra-acetic acid (EDTA) and the reducing power judged from 3-tert-butyl-4- hydroxyanisole (BHA). The data proposed that the bio-components from C. subavenium and C. kotoense act as natural antioxidants and play a potential role in cancer prevention. Meanwhile, the pure constituents will be used as leading compounds in the developments of useful cosmetic ingredients or future human disease therapies.