2-Dodecyl-6-methoxycyclohexa-2,5-diene-1,4-dione (DMDD), as well as variants, derivatives, analogs, modifications, and conjugates thereof, are identified as therapeutic agents for treating or preventing human cancers and precancerous conditions. DMDD can be isolated from the root of Averrhoa carambola L., commonly known as starfruit. Pharmaceutical and nutraceutical compositions, as well as dietary supplements, are provided, as are methods of administration and treatment.