A chemical study of the EtOAc extract of
Nemania bipapillata
(AT-05), an endophytic fungus isolated from the marine red alga
Asparagopsis taxiformis
-
Falkenbergia
stage, led to the isolation of five new botryane sesquiterpenes, including the diastereomeric pair (+)-(2
R
,4
S
,5
R
,8
S
)-(
1
) and (+)-(2
R
,4
R
,5
R
,8
S
)-4-deacetyl-5-hydroxy-botryenalol (
2
), (+)-(2
R
,4
S
,5
R
,8
R
)-4-deacetyl-botryenalol (
3
), one pair of diastereomeric botryane
nor
sesquiterpenes bearing an unprecedented degraded carbon skeleton, (+)-(2
R
,4
R
,8
R
)-(
4
) and (+)-(2
R
,4
S
,8
S
)-(
5
), which were named nemenonediol A and nemenonediol B, respectively, in addition to the known 4β-acetoxy-9β,10β,15α-trihydroxyprobotrydial (
6
). Their structures were elucidated using 1D and 2D NMR, HRESIMS and comparison with literature data of similar known compounds. The absolute configurations of
2
,
3
and
4
were deduced by comparison of experimental and calculated electronic circular dichroism (ECD) spectra, while those of
1
and
5
were assigned from vibrational circular dichroism (VCD) data. Compound
4
weakly inhibited acetylcholinesterase, whereas compound
1
inhibited both acetylcholinesterase and butyrylcholinesterase. Compounds
1
,
3
,
5
and
6
were tested against two carcinoma cell lines (MCF-7 and HCT-116), but showed no significant citotoxicity at tested concentrations (IC
50
> 50 µM).
