Recent Advances in Enone and NO-Releasing Derivatives of Oleanolic Acid with Anti-cancer Activity

Oleanolic acid (OA) is a natural pentacyclic triterpenoid acid with diverse biological activities including antiinflammation, suppression of tumor promotion, protection of the liver against toxic injury, and induction of differentiation. However, the potency of OA as an anti-cancer agent is relatively weak. Therefore, remarkable progress has been made in the modification of OA to improve its anti-cancer activity over the past few years. This paper reviews the progress mainly on anti-cancer activity of enone derivatives and nitric oxide (NO)-releasing derivatives of OA over the last decade.