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 for37 −39 .