1. Phillips DR, Rasbery JM, Bartel B, Matsuda SP (2006) Biosynthetic diversity in plant triterpene cyclization. Curr Opin Plant Biol 9:305–314
2. Suh N, Wang Y, Honda T, Gribble GW, Dmitrovsky E, Hickey WF, Maue RA, Place AE, Porter DM, Spinella MJ, Williams CR, Wu G, Dannenberg AJ, Flanders KC, Letterio JJ, Mangelsdorf DJ, Nathan CF, Nguyen L, Porter WW, Ren RF, Roberts AB, Roche NS, Subbaramaiah K, Sporn MB (1999) A novel synthetic oleanane triterpenoid, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid, with potent differentiating, antiproliferative, and anti-inflammatory activity. Cancer Res 59:336–341
3. Suh N, Roberts AB, Birkey Reffey S, Miyazono K, Itoh S, ten Dijke P, Heiss EH, Place AE, Risingsong R, Williams CR, Honda T, Gribble GW, Sporn MB (2003) Synthetic triterpenoids enhance transforming growth factor beta/Smad signaling. Cancer Res 63:1371–1376
4. Song M-K, Lee J-H, Ryoo I-G, Lee S-H, Ku S-K, Kwak M-K (2019) Bardoxolone ameliorates TGF-β1-associated renal fibrosis through Nrf2/Smad7 elevation. Free Radic Biol Med 138:33–42
5. Liby KT, Sporn MB (2012) Synthetic oleanane triterpenoids: multifunctional drugs with a broad range of applications for prevention and treatment of chronic disease. Pharmacol Rev 64:972–1003