Antiplasmodial and antitrypanosomal triterpenoids from Salvia hydrangea with rare carbon skeletons
Salvia hydrangea DC. ex Bentham, endemic to Iran, has been widely used in traditional Iranian medicine. Fractionation of the hexane extract of the aerial parts of this plant led to the isolation of hydrangdione-A (1) and hydrangdione-B (2), two new triterpenoids with rare carbon skeletons. Their structures were established on the basis of an extensive spectroscopic analysis, including 1D and 2D NMR, and by comparison of their NMR data with those of the related compounds. The IC50 of the compound 1 and 2 were determined against two parasites and rat myoblast (L6) cells. Hydrangdione-A (1) and hydrangdione-B (2) exhibited in vitro antiplasmodial activity against P. flaciparum K1 strains with IC50 value 1.43 and 0.18µM with great selectivity index (SI) 86.2 and 69.6. Also these compounds were tested against T. brucei rhodesiense STIB 900, they exhibited significant inhibition of growth with IC50 values of 4.33 and 15.92µM. Triterpenoids with these carbon skeletons are rare in the nature and have been previousely reperted only from two other species; Salvia bucharica Popov  and Perovskia abrotanoides Kar. . It is interesting to note that all three species belong to the flora of Iran and the genus Perovskia is a closely related to the genus Salvia.
In a suggested proposal for the biosynthesis of hydrangdione A and B they are presumably constructed by the addition of a monoterpenic unit (myrecene for hydrangedione A and trans-β-ocimene for hydrangdione B) to a diterpenic unit (an icetexone precursor) and this coupling may proceeds via Diels-Alder type reaction.
References:  Ahmad V U et al. (1999)J Org Chem 64: 8465–8467.
 Parvez A, et al. (1992)J OrgChem 57: 4339–4340.