Chemistry Reference
In-Depth Information
OCH
3
CO
2
H
N
O
CO
2
H
O
H
O
H
+
NH
3
CO
2
H
H
OH
N
−
O
2
C
O
NH
2
H
2
N
Cl
CO
2
H
HO
OH
H
H
444
HO
2
C
O
H
446
443
445
Girolline (
46
), which is a potent cytotoxin isolated from the sponge
Pseu-
daxinyssa cantharella
, inhibits protein synthesis (2).
2.2.2 Bromotyrosine Derivatives
Bromotyrosine-derived metabolites are often encountered in marine sponges
of the families Aplysinidae and Pseudoceratidae, in particular
Pseudoceratina
(=
Psammaplysilla
)
purpurea
. They show a variety of biological activities,
which include antimicrobial, enzyme inhibitory, and antifouling activities.
Psammaplysin A (
47
) is antimicrobial, cytotoxic, and antifouling, whereas
psammaplin A (
48
) is an inhibitor of histone deacetylase (2). The marine
sponge
Ianthella basta
synthesizes at least 25 bastadins that are linear or cyclic
peptides composed of four bromotyrosine residues [bastadin 5 (
49
)] and show
antimicrobial, cytotoxic, and enzyme inhibitory activities as well as interaction
with Ca
2+
channels (21).
OH
H
3
CO
Br
Br
Br
OH
O
O
N
N
HO
O
S
Br
NH
2
H
S
N
N
O
HO
O
H
O
Br
Br
OH
448
447
2.2.3 Linear Peptides
Sponges and tunicates frequently contain unusual linear and cyclic peptides;
those from the former source were reviewed in 1993 and 2002 (22, 23). To
avoid duplication, this review focuses on bioactive peptides isolated from other
sources and new findings. Gymnangiamide (
50
) is the first described peptide
from a hydroid (24). This pentapeptide from
Gymnangium regae
contains three
previously unknown amino acids. Although moderately cytotoxic, its structure is
reminiscent of dolastatin 10 (
51
), which is a powerful antitubulin agent of the
sea hare
Dolabella auricularia
(2). Actually, dolastatins are of cyanobacterial
