5 Steroids
Ergosterimide (390) (Fig. 22), a natural Diels–Alder adduct of ergosterol and
maleimide, was obtained from a 2.4% artificial sea salt-containing GPY medium
fermentation of Aspergillus niger EN-13, a fungal endophyte that was isolated from
fresh tissue of the marine brown alga Colpomenia sinuosa collected off the Qingdao
coastline [119]. Fermentation of Aspergillus ochraceus EN-31, which was isolated
from the marine brown alga Sargassum kjellmanianum collected from the Dalian
coastline, in a sea salt-containing liquid medium, yielded a pentalactone-containing
norsteroid, 7-nor-ergosterolide (391), together with two steroids, 3β,11αdihydroxyergosta-8,24(28)-dien-7-one (392) and 3β-hydroxyergosta-8,24(28)dien-7-one (393). 7-nor-Ergosterolide (391) displayed cytotoxicity against the
NCI-H460, SMMC-7721, and SW1990 cell lines with IC 50 values of 12.1, 16.9,
and 67.6 μM, respectively, while compound 392 showed only weak cytotoxicity
against the SMMC-7721 cell line with an IC 50 value of 65.4 μM [120].
The endophyte Aspergillus versicolor pt20 was isolated from the marine brown
alga Sargassum thunbergii collected from Pingtan Island. Fermentation of this
AcO
COOH
HO
378 ((+)-penicimonoterpene)
O
O
O
OH
383 (ophiobolin U)
O
OH
384 (ophiobolin V)
OH
HO
385 (ophiobolin W)
O
HO
O
HO
386 (sesteralterin)
HOOC
AcO
OH
HOOC
HO
HOOC
OH
O
387
388
389
O
O
O
OH
379 (nectriapyrone C)
380 (nectriapyrone D)
O
O
O
OH
381 (6α-21-deoxyophiobolin G) 382 (6α-16,17-dihydro-21-deoxyophiobolin G)
Fig. 21 Structures of other terpenes
116
Z. Liu et al.