Part A | 7.2
180 Part A Marine Flora and Fauna
marine animals, most of which form colonies mainly in
tropical waters composed of hundreds or thousands of
polyps; polyps cover a soft skeleton composed of a protein/calcium carbonate material (> 60% of organic matter). Cnidaria, one of the largest phyla consists of three
classes, among which Anthozoa is the largest [7.4, 5].
Among Cnidaria, 21% of the species contain potential marine biomedical compounds [7.6]. Almost 50%
of octocorals as members of Cnidaria have been reported to produce toxins; about 60% of their extracts are
bioactive molecules with medicinal potential [7.7–10].
Published records state that 1117% of potential new
drugs undergoing preclinical stage from 1998 to 2002,
originate from octocorals. From the soft coral species
investigated up to 2008, more than 30% exhibited cytotoxic activity [7.11], suggesting production of potential
medicinals. A similar percentage (30%) was presented
in [7.12], where crude extracts were screened from 20
octocorals displaying cytotoxic and antimycobacterial
activities (60%, Figs. 7.1–7.10).
7.2 Potential Pharmaceuticals from Soft Corals
Octocorals lack toxic stinging nematocysts, as well as
a rigid protective skeleton common to scleractinians,
but possess allelopathic capabilities [7.13]. Using allelopathic chemicals, sessile soft corals compete for
space, reduce their palatability by producing terpenoids,
and reduce fouling by chemical substances and mucus [7.14]. These allelopathic secondary metabolites,
especially terpenes, also protect against predators, infections and injuries, and play a range of physiological
roles [7.5, 15].
Structurally diverse compounds including diterpenes, prostaglandins, and steroids described in octocorals [7.16–18] render these animals rich sources
of steroids, terpenoids, and other types of secondary
metabolites, including a large variety of sesquiterpenoids and diterpenoids [7.8, 19]. Octocorals, unlike
sponges, are capable of rapidly synthesizing terpenes
de novo [7.19]. Similarly, it was reported in [7.20]
and [7.21] that toxins are secreted more or less continuously in several species of soft corals.
In a comprehensive study, the antimicrobial activity
of extracts of several of the most dominant stony (scleractinian) and soft (alcyonacean) coral species from
the coral reef of Eilat (northern Red Sea) was compared against indigenous bacteria. The results revealed
substantial variability in antimicrobial activity of the
extracts from hard and soft corals. Five out of six (83%)
Red Sea alcyonacean soft corals showed considerable
antimicrobial activity against the test bacteria, whereas
none of the extracts of the six stony corals tested inhibited the test bacteria. It, therefore, appears that soft
and hard corals have developed different means to
combat potential microbial infections. Antibiotic compounds in alcyonacean soft corals are used to combat
microbial attack, whereas stony corals seem to rely
on other means [7.22]. Nonetheless, further research
on hard (scleractinian) corals revealed bioactive compounds and the biological role of terpenes in hard corals
as well. Hence, in this chapter, the pharmaceutical potential of soft and hard coral species will be described
separately.
De novo biosynthesis of sterols has also been stated
as an important mechanism in octocorals [7.23]. Until
early 2009, 561 new polar steroids had been reported
from 16 families of octocoral species. Soft corals contribute predominantly as containers of the largest number of marine polar steroids; unusual sterols are the only
extensive products of a large number of coral species.
Particularly, the Alcyonarian corals of the genera Sarcophyton, Sinularia, and Lobophytum are very rich in
sterols [7.24].
Soft (octo)corals (order Alcyonacea) and gorgonians (order Gorgonacea), with fewer examples from
zoanthids (order Zoantharia) and sea pens (order Pennatulacea), have presented the majority of interesting
metabolites. Of the six orders in the subclass Octocorallia, the Alcyonacea, which are fleshy soft corals,
and Gorgonaceae (sea fans and sea whips) are by
far the most widely distributed and studied. In Alcyonaceae, Alcyoniidae and Nephtheidae are the largest
families. Alcyonaria possess a diverse array of chemical compounds and are particularly rich in isoprenoids,
including terpenes, carotenoids, and steroids [7.25–
27]; hence, they were one of the first marine groups
to be systematically screened for secondary metabolites [7.28]. Each species of octocorals seems to have
its own specific set of compounds [7.29].
Potential therapeutics identified in soft corals include anticancer agents, immunomodulators, and useful
antifouling agents. The striking presence of cembranoid diterpenes in soft corals outnumbers the occasional occurrence in other taxa, which are also interesting in terms of pharmacological research. They show
significant biological activity, including antimicrobial,
180 Part A Marine Flora and Fauna
marine animals, most of which form colonies mainly in
tropical waters composed of hundreds or thousands of
polyps; polyps cover a soft skeleton composed of a protein/calcium carbonate material (> 60% of organic matter). Cnidaria, one of the largest phyla consists of three
classes, among which Anthozoa is the largest [7.4, 5].
Among Cnidaria, 21% of the species contain potential marine biomedical compounds [7.6]. Almost 50%
of octocorals as members of Cnidaria have been reported to produce toxins; about 60% of their extracts are
bioactive molecules with medicinal potential [7.7–10].
Published records state that 1117% of potential new
drugs undergoing preclinical stage from 1998 to 2002,
originate from octocorals. From the soft coral species
investigated up to 2008, more than 30% exhibited cytotoxic activity [7.11], suggesting production of potential
medicinals. A similar percentage (30%) was presented
in [7.12], where crude extracts were screened from 20
octocorals displaying cytotoxic and antimycobacterial
activities (60%, Figs. 7.1–7.10).
7.2 Potential Pharmaceuticals from Soft Corals
Octocorals lack toxic stinging nematocysts, as well as
a rigid protective skeleton common to scleractinians,
but possess allelopathic capabilities [7.13]. Using allelopathic chemicals, sessile soft corals compete for
space, reduce their palatability by producing terpenoids,
and reduce fouling by chemical substances and mucus [7.14]. These allelopathic secondary metabolites,
especially terpenes, also protect against predators, infections and injuries, and play a range of physiological
roles [7.5, 15].
Structurally diverse compounds including diterpenes, prostaglandins, and steroids described in octocorals [7.16–18] render these animals rich sources
of steroids, terpenoids, and other types of secondary
metabolites, including a large variety of sesquiterpenoids and diterpenoids [7.8, 19]. Octocorals, unlike
sponges, are capable of rapidly synthesizing terpenes
de novo [7.19]. Similarly, it was reported in [7.20]
and [7.21] that toxins are secreted more or less continuously in several species of soft corals.
In a comprehensive study, the antimicrobial activity
of extracts of several of the most dominant stony (scleractinian) and soft (alcyonacean) coral species from
the coral reef of Eilat (northern Red Sea) was compared against indigenous bacteria. The results revealed
substantial variability in antimicrobial activity of the
extracts from hard and soft corals. Five out of six (83%)
Red Sea alcyonacean soft corals showed considerable
antimicrobial activity against the test bacteria, whereas
none of the extracts of the six stony corals tested inhibited the test bacteria. It, therefore, appears that soft
and hard corals have developed different means to
combat potential microbial infections. Antibiotic compounds in alcyonacean soft corals are used to combat
microbial attack, whereas stony corals seem to rely
on other means [7.22]. Nonetheless, further research
on hard (scleractinian) corals revealed bioactive compounds and the biological role of terpenes in hard corals
as well. Hence, in this chapter, the pharmaceutical potential of soft and hard coral species will be described
separately.
De novo biosynthesis of sterols has also been stated
as an important mechanism in octocorals [7.23]. Until
early 2009, 561 new polar steroids had been reported
from 16 families of octocoral species. Soft corals contribute predominantly as containers of the largest number of marine polar steroids; unusual sterols are the only
extensive products of a large number of coral species.
Particularly, the Alcyonarian corals of the genera Sarcophyton, Sinularia, and Lobophytum are very rich in
sterols [7.24].
Soft (octo)corals (order Alcyonacea) and gorgonians (order Gorgonacea), with fewer examples from
zoanthids (order Zoantharia) and sea pens (order Pennatulacea), have presented the majority of interesting
metabolites. Of the six orders in the subclass Octocorallia, the Alcyonacea, which are fleshy soft corals,
and Gorgonaceae (sea fans and sea whips) are by
far the most widely distributed and studied. In Alcyonaceae, Alcyoniidae and Nephtheidae are the largest
families. Alcyonaria possess a diverse array of chemical compounds and are particularly rich in isoprenoids,
including terpenes, carotenoids, and steroids [7.25–
27]; hence, they were one of the first marine groups
to be systematically screened for secondary metabolites [7.28]. Each species of octocorals seems to have
its own specific set of compounds [7.29].
Potential therapeutics identified in soft corals include anticancer agents, immunomodulators, and useful
antifouling agents. The striking presence of cembranoid diterpenes in soft corals outnumbers the occasional occurrence in other taxa, which are also interesting in terms of pharmacological research. They show
significant biological activity, including antimicrobial,