Taraxastanes

Twenty-three triterpenoid hydrocarbons isolated from ferns were screened [67]. The following eight exhibited strong inhibitory effects at lxlO2 mol ratio compound/TPA with >80% viability of Raji cells [67]. They are multiflor-8-ene (220 45%), multiflor-9(ll)-ene (228 41%), taraxastane (237 43%), taraxerane (241 37%), glutin-5(10)-ene (244 52%), hop-17(2l)-ene (275 51%), neohop-13(18)-ene (277 37%), and neohop-12-ene (278 37%). It should be mentioned that the inhibitory... 

Agrawal, P. K. Bishnoi, V. Studies on Indian medical plants. 42. Sterol and taraxastane derivatives from Artemisia annua and a rational approach based upon C-13 NMR for the identification of skeletal type of amorphane sesquiterpenoids. Indian J. Chem., 1996, 35B 86-88. 

Plant-derived triterpenoids are overtly abundant in sediments from the late Mesozoic onwards. These include oleanane (61), lupane (62), and taraxastane (63). There is a clear relationship between these compounds and triterpenoid precursors such as /3-amyrin (64)... 

This Reporter prefers to name these compounds as derivatives of taraxastane rather than taraxane since this is less confusing with respect to the taraxerane group. 

The main kind of anti-inflammatory triterpenes isolated have oleanane, ursane, taraxastane, lupane and lanostane skeletons (Table 1). Some minor compounds such as hopane are included in other structural groups. Other anti-inflammatory triterpenes like the different cucurbitacins are not included in this review because of their high toxicity. 

The active taraxastane triterpenes are included in two groups —the taraxast-20-ene, or taraxastene type (Table 9) and its isomer taraxast-20(30)-ene, or /-taraxastene type (Table 10). 

The participation of C-28 oxygen functions in bromine addition to the double bond of -taraxastenes and the isomerization of 28-benzoyloxy-20a,2la-epoxy taraxastanes form the subjects of recent papers. 

To date, about 25 taraxastanes have been isolated, predominantly from Asteraeeae Representatives inelude (+)-20-Taraxasten-3p-ol (v /-taraxasterol) and (+)-20(30)-taraxasten-3p,16p-diol (amidenediol) from lion s tooth Taraxacum officinale and Arnica montana as well as 20-taraxasten-3p,16p-diol (faradiol) from Arnica mon-tana, Tussilago farfara, Senecio alpinus and gold-bloom Calendula officinalis (all Asteraeeae). 

Taraxa sterol, a-lactucerol, a-anthesterol a simple, unsaturated, pentacyclic triterpene alcohol, M, 426.73, m.p. 227 °C [a]D-r50°, structurally a derivative of the parent hydrocarbon, 5a-taraxastane. It occurs as the acetate in the latex of the dandelion (Taraxacum officinale) and other members of the Compo-sitae. 

Germanicane and taraxastane are minor groups. Morolic acid (534) from heartwood of Mora excelsa and (//-taraxasterol (535) from roots of Taraxacum officinale are examples of these types present in woody parts of plants (228). 

---