The natural product curcumin has gained considerable attention in recent years for its multiple pharmacological activities, but more efforts are needed to understand how curcumin can have these pharmacological effects considering its low bioavailability. In addition, it is unclear how curcumin exerts inhibitory effects against numerous enzymes, especially those that cannot accommodate curcumin within recognized binding pockets. By analyzing the similarities between the biological activities of curcumin and its degradation products against diseases such as Alzheimer's disease and cancer, as well as the preferential inhibition of some enzymes by degradation products, it appears that the bioactive degradation products may contribute to the pharmacological effects of curcumin. This possibility should be given full attention when elucidating the pharmacology of this promising natural product for various diseases.