Chemistry Reference
In-Depth Information
metabolites are often encountered as sponge metabolites; the first example
is avarol (
120
), which was isolated from
Dysidea avara
. Several related
compounds have been isolated from dictyoceratid sponges. They show a wide
range of bioactivities, for example, antimicrobial, antitumor, anti-inflammatory,
and enzyme inhibitory.
HO
H
HO
H
OH
O
O
OH
HO
H
H
118
119
117
120
118
2.4.2 Diterpenoids
Brown algae are rich in diterpenoids, which can be classified into three groups,
namely “xenicanes,” “extended sesquiterpenes,” and “dolabellanes,” which are
represented by dictyotadial (
121
) from
Dictyota crenulata
, spatol (
122
)from
Spatoglossum schmittii
, and amijidictyol (
123
) from
Dictyota linearis
, respec-
tively. These terpenes are involved in chemical defense. Red algae contain bromi-
nated diterpenes of several established skeletal types.
Spongian diterpenes are a chemical marker for dictyoceratid and dendrocer-
atid sponges (37). The first example of a spongian diterpene is isoagatholactone
(
124
) isolated from
Spongia officinalis
. In addition to those possessing a basic
spongian skeleton, a wide variety of rearranged spongian diterpenoids have been
reported, which include gracilin B (
125
) from
Spongionella gracilis
. Many spon-
gian diterepenes are antimicrobial and cytotoxic.
O
H
O
H
OHC
OHC
O
H
O
H H
O
H
H
OH
H
O
124
123
122
121
Again, soft corals and gorgonians are a rich source of diterpenoids of 19
structural classes, some of which are specific to them (35, 36). Besides tobacco
plants, cembranoid diterpenes are limited to soft corals. Lophotoxin (
126
) iso-
lated from sea whips of the genus
Lophogorgia
is a sodium channel inhibitor (3).
Xenicin (
127
) from the soft coral
Xenia elongata
and briarein A (
128
)fromthe
gorgonian
Briareum asbestinum
represent non-cembranolide diterpenes. Diter-
penoids of these classes show antimicrobial, cytotoxic, and insecticidal activities.
Pseudopterosin A (
129
), which is a diterpene glycoside isolated from the sea whip
Pseudopterogorgia elisabethae
, shows anti-inflammatory activity by inhibiting
release of leukotriene B
2
from leukocytes (2, 35). A more interesting class of
