Chemistry Reference
In-Depth Information
Clavelina picta
, is marginally cytotoxic. Stellettamine A (
108
), which is an
indolizidine derivative from a sponge
Stelletta
sp., is antifungal and cytotoxic.
It also inhibits calmodulin (12). Lepadiformine (
109
), which has a similar
structural feature isolated from the tunicate
Clavelina inoluccensis
, inhibits K
+
channels (33).
OMe
OMe
HO
H
O
AcO
O
H
H
H
H
O
NMe
NMe
H
N
N
N
OH
H
HO
MeO
H
O
S
O
OH
O
O
O
O
MeO
O
NH
107
HO
106
105
Me
N
+
X
−
N
N
H
O
HO
108
109
2.3.10 Steroidal Alkaloids
Steroidal alkaloids belong to a rare class of marine natural products. Plakinamine
A(
110
), which is an antimicrobial metabolite from a sponge
Plakina
sp., is the
first steroidal alkaloid isolated from marine organisms. Cephalostatins and ritter-
azines are unprecedented dimeric steroidal alkaloids isolated from the hemichor-
date
Cephalodiscus grichristii
and the tunicate
Ritterella tokioka
, respectively
(1, 30). They are specific to marine metabolites. Cephalostatin 1 (
111
) and rit-
terazine B (
112
) are highly cytotoxic, but their mode of action remains to be
elucidated.
OH
O
HO
OH
O
OH
H
H
N
N
H
H
H
H
N
H
H
H
2
N
H
O
O
111
0
O
111
OH
