2.7. Miscellaneous sesquiterpenoids
Curcumanes A (37 ) and B (38 ) are two novel bicyclic sesquiterpenoids with significant vasorelaxant activity, which have been isolated from Curcuma longa ,[58] a traditional Chinese medicine for promoting blood circulation.[59] Structurally, 37 and 38 possess unprecedented skeletons with a dicyclo[3.2.1]octane and a dicyclo[3.3.1]nonane moiety, respectively. Biosynthetically, the cyclization from C-1′′ to C-1′ and C-1′′ to C-5 of a bisabolane derivative, respectively, are key steps in the proposed biogenetic pathways of 37 and 38(Fig. 9), respectively.
A pair of caged norsesquiterpenoidal enantiomers (±)-preuisolactone A (±39 ), featuring an unprecedented tricyclo[4.4.01,6.02,8]decane carbon scaffold determined by X-ray crystallography, have been found from the plant endophytic fungus preussia isomera .[60-62] A plausible biosynthetic pathway for (±)-39 has been proposed (Fig. 9). In addition, (±)-39 exhibited remarkable antibacterial activity againstMicrococcus luteus with an MIC value of 10.2 μ M.
Fig. 9. Proposed biosynthetic pathways for3739 .