Microbes are the single-celled marine phytoplankton which constitutes 90% of
the ocean’s total biomass. They are tiny microscopic organisms. Bacteria, fungi,
and plankton along with the viruses originate from them. They are in billion
inhabiting in seawater. Many marine microbes constitute biochemical diversity
along with a reservoir of novel drugs. They are considered as essential sources for
drug discovery and development. Marine bacteria are associated with the development of novel drugs like antibiotics and other pharmaceuticals. Meroterpenoids
are the class of secondary metabolites in which the terpenoid moieties are linked to
molecules from different biosynthetic pathways (Rahman and McFadden 2011).
They include quinones with prenylated naphthoquinones and reduced hydroquinone analogues and are mainly derived from marine fungi and actinomycetes.
Meroterpenoids exert anti-cancer activity. Polyketide synthases belong to a class of
enzymes associated with the biosynthesis of secondary metabolites and show potent
anti-cancer activity. Actinomycetes come under the systematic groups of secondary
metabolite producers. They exert various biological activities including anti-cancer
property (Huheihel et al. 2002).
Arisostatin A and arisostatin B, glycosylated polyketides are isolated from
the Micromonospora sp.. They come under the class of tetrocarcin–type cytotoxic
compounds and especially Arisostatin A exhibit potent anti-cancer activity because
of its cytotoxic effect on human cancer cells. It also activates caspase 3, a key
effector protease responsible for apoptosis induction (Wang et al. 2013).
Toluquinol, isolated from marine fungus interferes with one of the factors
causing cancer by impairing the unlimited replicative potential, characteristic features of tumour cells. It suppresses the proliferation of the promyelocytic leukemia
cell line, fibrosarcoma cell, and colon adenocarcinoma cell. Diketopiperazines,
isolated from marine-derived fungi, have gained a lot of attention from the
researchers’ attention because of their varying chemical structure and biological
activities. Halimide ((-)-phenylahistin), originated from Aspergillus ustus, is a
fungal prenylated Diketopiperazines showed anticancer activity by arresting the cell
cycle of cancer (P388) in its G2/M phase (Schumacher et al. 2010).
Tunicates or urochordates, comes under subphylum Tunicata or Urochordata.
They have been shown as a primitive model organism to study immunodefense
since the innate immune system has been hypothesized as an important functional
component that may partially explain the lack of metastatic tumors in invertebrates
(Janakiram et al. 2010). Marine-derived compounds such as didemnin B, Aplidine,
and ecteinascidin have reached clinical trials for antitumor activity. Didemnin B,
isolated from Trididemnum solidum, is a cyclic depsipeptide and today it is recognized as a first marine-originated compound to enter phases I and II clinical trials.
The phase II studies suggest the complete or partial remissions with non-Hodgkins
lymphoma, but due to cardiotoxicity as a side effect, scientists chose didemnin B for
further study. The closely related dehydrodidemnin B (DDB, Aplidine) is isolated
from Aplidium albicans in 1988. Spectroscopic studies assign a structural formula
in which a pyruvyl group in dehydrodidemnin B is replaced by the lactyl group in
Didemnin B and syntheses of dehydrodidemnin B have been achieved. It is also
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the ocean’s total biomass. They are tiny microscopic organisms. Bacteria, fungi,
and plankton along with the viruses originate from them. They are in billion
inhabiting in seawater. Many marine microbes constitute biochemical diversity
along with a reservoir of novel drugs. They are considered as essential sources for
drug discovery and development. Marine bacteria are associated with the development of novel drugs like antibiotics and other pharmaceuticals. Meroterpenoids
are the class of secondary metabolites in which the terpenoid moieties are linked to
molecules from different biosynthetic pathways (Rahman and McFadden 2011).
They include quinones with prenylated naphthoquinones and reduced hydroquinone analogues and are mainly derived from marine fungi and actinomycetes.
Meroterpenoids exert anti-cancer activity. Polyketide synthases belong to a class of
enzymes associated with the biosynthesis of secondary metabolites and show potent
anti-cancer activity. Actinomycetes come under the systematic groups of secondary
metabolite producers. They exert various biological activities including anti-cancer
property (Huheihel et al. 2002).
Arisostatin A and arisostatin B, glycosylated polyketides are isolated from
the Micromonospora sp.. They come under the class of tetrocarcin–type cytotoxic
compounds and especially Arisostatin A exhibit potent anti-cancer activity because
of its cytotoxic effect on human cancer cells. It also activates caspase 3, a key
effector protease responsible for apoptosis induction (Wang et al. 2013).
Toluquinol, isolated from marine fungus interferes with one of the factors
causing cancer by impairing the unlimited replicative potential, characteristic features of tumour cells. It suppresses the proliferation of the promyelocytic leukemia
cell line, fibrosarcoma cell, and colon adenocarcinoma cell. Diketopiperazines,
isolated from marine-derived fungi, have gained a lot of attention from the
researchers’ attention because of their varying chemical structure and biological
activities. Halimide ((-)-phenylahistin), originated from Aspergillus ustus, is a
fungal prenylated Diketopiperazines showed anticancer activity by arresting the cell
cycle of cancer (P388) in its G2/M phase (Schumacher et al. 2010).
Tunicates or urochordates, comes under subphylum Tunicata or Urochordata.
They have been shown as a primitive model organism to study immunodefense
since the innate immune system has been hypothesized as an important functional
component that may partially explain the lack of metastatic tumors in invertebrates
(Janakiram et al. 2010). Marine-derived compounds such as didemnin B, Aplidine,
and ecteinascidin have reached clinical trials for antitumor activity. Didemnin B,
isolated from Trididemnum solidum, is a cyclic depsipeptide and today it is recognized as a first marine-originated compound to enter phases I and II clinical trials.
The phase II studies suggest the complete or partial remissions with non-Hodgkins
lymphoma, but due to cardiotoxicity as a side effect, scientists chose didemnin B for
further study. The closely related dehydrodidemnin B (DDB, Aplidine) is isolated
from Aplidium albicans in 1988. Spectroscopic studies assign a structural formula
in which a pyruvyl group in dehydrodidemnin B is replaced by the lactyl group in
Didemnin B and syntheses of dehydrodidemnin B have been achieved. It is also
602
D. Pal and K. Raj