Marine Pharmacology in 2009–2011: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, and Antiviral Activities; Affecting the Immune and Nervous Systems, and other Miscellaneous Mechanisms of Action †

The peer-reviewed marine pharmacology literature from 2009 to 2011 is presented in this review, following the format used in the 1998–2008 reviews of this series. The pharmacology of structurally-characterized compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacological activities were reported for 102 marine natural products. Additionally, 60 marine compounds were observed to affect the immune and nervous system as well as possess antidiabetic and anti-inflammatory effects. Finally, 68 marine metabolites were shown to interact with a variety of receptors and molecular targets, and thus will probably contribute to multiple pharmacological classes upon further mechanism of action studies. Marine pharmacology during 2009–2011 remained a global enterprise, with researchers from 35 countries, and the United States, contributing to the preclinical pharmacology of 262 marine compounds which are part of the preclinical pharmaceutical pipeline. Continued pharmacological research with marine natural products will contribute to enhance the marine pharmaceutical clinical pipeline, which in 2013 consisted of 17 marine natural products, analogs or derivatives targeting a limited number of disease categories.


Introduction
The current article presents a systematic review of the preclinical pharmacology of the marine natural products literature in 2009-2011, with a similar format to previous reviews [1][2][3][4][5][6][7], and which resulted from extensive searches of several databases, including Marinlit, PubMed, Current Contents ® and Chemical Abstracts ® . We have limited this review to the peer-reviewed literature that reported bioactivity or pharmacology of structurally characterized marine chemicals, and have continued to use a modification of Schmitz's chemical classification [8] to assign marine structures to six major chemical classes, namely, polyketides, terpenes, peptides, alkaloids, shikimates, and sugars. The preclinical antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacology of marine chemicals is presented in Table 1, with the corresponding structures shown in Figure 1. Marine compounds that affect the immune and nervous systems, as well as those with antidiabetic and anti-inflammatory effects are shown in Table 2, with their corresponding structures presented in Figure 2. Finally, marine compounds that have been demonstrated to affect a wide variety of cellular and molecular targets are exhibited in Table 3, and their structures presented in Figure 3. Several publications during 2009-2011 described extracts or as yet structurally uncharacterized marine compounds, and although they have been excluded from the current review, they certainly deserve further investigation because they report novel and interesting in vitro or in vivo preclinical pharmacology: antimicrobial and antistaphylococcal biofilm activity of three 5-kDa peptides isolated from coelomocyte effector cells of the sea urchin Paracentrotus lividus that could benefit patients with medical device-associated infections [9]; an antibacterial polyunsaturated fatty acid, eicosapentanoic acid, isolated from extracts of the marine diatom Phaeodactylum tricornutum with activity against a range of Gram-positive and Gram-negative bacteria, including multidrug-resistant Staphyloccus aureus [10]; potent anticoagulant activity of sulfated polysaccharides isolated from the Brazilian brown seaweed Dictyota cervicornis, which was close to that of clinically used low molecular weight heparin [11]; potent anticoagulant activity of a sulfated polysaccharide isolated from the Chinese green seaweed Monostroma latissimum by a mechanism involving thrombin inhibition in the presence of heparin cofactor II [12]; in vitro antileishmanial activity of dichloromethane extracts of a Tunisian sponge Sarcotragus sp., which demonstrated concomitant morphological alterations of Leishmania major promastigotes in vitro [13]; in vivo and in vitro antifilarial activity of the marine sponge Haliclona exigua extracts against adult nematode Brugia malayi, a parasite that may cause lymphatic filariasis [14]; significant nontoxic and anti-herpes simplex virus HSV-1 and HSV-2 activity in sulfated polysaccharide extracts isolated from four species of red and brown marine algae from New Zealand [15]; anti-herpes simplex virus HSV-1 activity in high molecular weight exopolysaccharides purified from the French marine sponge Celtodoryx girardae and its symbiotic bacteria [16]; anti-inflammatory activity of the crude extracts and fractions of the Mediterranean sponge Spongia officinalis in the in vivo rat carrageenan-induced paw edema assay [17]; in vivo anti-inflammatory activity in polyphenolic extracts from the red alga Laurencia undulata resulting in significant inhibition of asthmatic reactions [18]; in vitro anti-inflammatory effect in an ethanolic extract from the brown alga Ishige okamurae via inhibition of NF-κB transcription factor [19]; induction of oxidative death in a human glioma cell line through a caspase-9 apoptotic pathway by extracts from the marine sponge Polymastia janeirensis [20]; apoptotic activity in extracts from the marine diatom Cocconeis scutellum associated with activation of caspases-8 and -3 in human breast cancer lines [21]; human neutrophil anti-elastase activity of purified sulfated polysaccharides from the red alga Delesseria sanguinea [22]; high antioxidant activity in methanolic extracts of the Korean red alga Polysiphonia morrowii that protected against hydroxyl radical-induced DNA damage in vitro [23]; antioxidant activity in phenolic compounds from the marine alga Halimeda monile that protected against chemically induced rat liver injury in vivo [24]; significant antioxidant properties of polysaccharides from a marine fungus Penicillium sp. F23-2 against superoxide and hydroxyl radicals [25]; in vitro antioxidant activities of acetylated, phosphorylated and benzoylated derivatives of the marine red alga Porphyra haitanensis phorphyran [26]; acceleration of skin wound healing by amino acids isolated from the mollusc Rapana venosa suggesting a possible therapeutic use in skin burns [27]; neuroprotective effects in extracts of the South Indian green seaweed Ulva reticulata that inhibited both acetyl-and butyryl-cholinesterases, and was comparable to agents currently approved for Alzheimer's disease treatment [28]. Table 1 presents the 2009-2011 preclinical pharmacological research on the antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities of the marine natural products  shown in Figure 1.

Antibacterial Activity
During 2009-2011, 35 studies reported antibacterial marine natural products isolated from a diverse group of marine bacteria, ascidians, bryozoans, sponges, soft corals and algae, a persistent effort on which we have reported previously [7], and which continues to contribute to the global health challenge posed by drug-resistant bacteria.
Only four papers reported molecular mechanism of action studies with marine antimicrobial compounds. Plaza and colleagues investigated bisdiarylbutene macrocycle chrysophaentin A (1) from the chrysophyte alga Chrysophaeum taylori that potently inhibited Gram positive methicillin-resistant Staphylococus aureus (minimum inhibitory concentration [MIC] 50 = 1.5 μg/mL) and vancomycin-resistant Enterococcus faecium (MIC 50 = 2.9 μg/mL) by binding and inhibiting GTPase activity of the essential bacterial cell division protein FtsZ [29]. Two studies contributed to the ongoing search of quorum sensing antagonists as potentially novel antimicrobial drugs: Teasdale and colleagues extended the pharmacology of two previously described phenethylamide metabolites isolated from a marine Gram positive Halobacillus salinus strain [30]. One of these compounds, 3-methyl-N-(2′-phenylethyl)-butyramide (2) interfered with quorum sensing-regulated activities (e.g., bioluminescence inhibition IC 50 = 9 μg/mL) in several Gram negative species. Kwan and colleagues isolated a small cyclopropane-containing fatty acid, lyngbyoic acid (3) from the marine cyanobacterium Lyngbya cf. majuscula [31] that affected both quorum sensing pathways (acylhomoserine lactone receptor LAsR (IC 50 = 100 µM) as well as gene expression in Pseudomonas aeruginosa. Jeon and colleagues extended the pharmacology of the pyrroloiminoquinone alkaloids of the discorhabdin class isolated from the Korean marine sponge Sceptrella sp. [32]. A new alkaloid (−)-discorhabdin Z (4), possessing a unique hemiaminal group, inhibited sortase A (IC 50 = 6.5 μM), a bacterial transpeptidase that has been shown to covalently attach proteins to the bacterial cell wall and has become an important antimicrobial target.

Antifungal Activity
Ten studies during 2009-2011 reported on the antifungal activity of several novel marine natural products isolated from marine bacteria, sponges and bryozoa, a slight decrease from our last review [7], and previous reviews of this series.
As shown in Table 1, only two reports described antifungal marine chemicals with novel mechanisms of action. DiGirolamo and colleagues identified two new sulfated sterols, geodisterol-3-O-sulfate (34) and 29-demethylgeodisterol-3-O-sulfate (35), in a marine sponge Topsentia sp. [52], which enhanced the activity of the clinically used triazole antifungal agent fluconazole by reversing efflux pump-mediated fluconazole resistance in Candida albicans. Nishimura and colleagues extended the pharmacology of the bicyclic antifungal dodecapeptide theonellamide F (36) previously isolated from a sponge Theonella sp. [53]. Chemical-genomic profiling analysis together with detailed subcellular localization studies determined that the antifungal theonellamides represent a new class of sterol-binding molecules that induce membrane damage and activate Rho1-mediated 1,3-β-D-glucan synthesis.
These marine compounds may provide novel pharmacological leads thus contributing to the global search for clinically useful antifungal agents.

Antiprotozoal and Antituberculosis Activity
As shown in Table 1, during 2009-2011 thirty two studies contributed to novel findings on the antiprotozoal and antituberculosis pharmacology of structurally characterized marine natural products, a considerable increase from previous 1998-2008 reviews [7].
Malaria, which is caused by protozoa from the genus Plasmodium (P. falciparum, P. ovale, P. vivax and P. malariae), affects millions of people worldwide. Contributing to the global search for novel antimalarial drugs, and as presented in Table 1, twenty six novel marine molecules were shown during 2009-2011 to possess antimalarial activity, although mechanism of action studies were reported for only two compounds. Taglialatela-Scafati and colleagues extended the molecular pharmacology of plakortin (43), isolated from the Caribbean marine sponge Plakortis simplex, which potently inhibited CQ-resistant strains of Plasmodium falciparum [58]. Plakortin was observed to give rise to toxic carbon radicals which were ultimately "responsible for subsequent reactions leading to Plasmodium death". Lebouvier and colleagues reported that the homogentisic acid derivative 44 from a Vanuatu marine sponge Pseudoceratina sp. was moderately active in vitro against FcB1 P. falciparum strain, while concomitantly inhibiting the specific protein kinase pfnek-1 of the parasite (IC 50 = 1.8 μM). Thus, compound 44 "could serve as a model for the development of new pfnek-1 inhibitors" [59].
Eighteen marine compounds were reported to possess activity against other protozoa thus contributing to the ongoing global search for novel agents for the so-called neglected diseases, namely leishmaniasis (caused by several species of the genus Leishmania), amebiasis, trichomoniasis, African sleeping sickness (caused by Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense) and American sleeping sickness or Chagas disease (caused by Trypanosoma cruzi). Dos Santos and colleagues reported that a 4-acetoxydolastane diterpene (64) isolated from the Brazilian brown alga Canistrocarpus cervicornis [73] dose-dependently inhibited promastigote, axenic amastigote and intracellular amastigote forms of Leishmania amazonensis (IC 50 = 2.0, 12.0 and 4.0 μg/mL, respectively) by extensive mitochondrial damage and lipid peroxidation.
As shown in Table 1, four novel marine natural products contributed to the global search for novel antituberculosis agents, a decrease from our previous reviews [7].
Vicente and colleagues extended the pharmacology of the known compound hymenidin (87) [85]. Wei and colleagues isolated tetracyclic bis-piperidine alkaloid neopetrosiamine A (62) from the Puerto Rican marine sponge Neopetrosia proxima which inhibited growth (MIC = 7.5 μg/mL) of the pathogenic strain Mycobacterium tuberculosis H 37 Rv [71]. Although all of these studies demonstrate that marine alkaloids and peptides may potentially become novel antituberculosis leads, further studies are required to determine the molecular pharmacology of these compounds.

Antiviral Activity
As shown in Table 1, three reports were published during 2009-2011 on the antiviral pharmacology of novel marine natural products against human cytomegalovirus and herpes simplex virus. Cheng and colleagues purified two new diterpenoids, gyrosanols A and B (91,92), and two novel cembranoids, lobophynin C and ehrenberoxide B (93,94), from the Taiwanese soft corals Sinularia capillosa and Sarcophyton ehrenbergi, respectively, which inhibited the herpes virus-5 or cytomegalovirus (HCMV) (IC 50 = 2.6-5.8 μM), an interesting preclinical contribution because HCMV infections may be life-threatening in immunocompromised patients [86,87]. Palem and colleagues extended the pharmacology of the known β-carboline alkaloid manzamine A (95), isolated from an Indo-Pacific sponge Acanthostrongylophora sp., by demonstrating the compound inhibited HSV-1 infection (apparent IC 50 = 1 μM) in rabbit corneal cells by affecting viral immediate-early gene transcription [88].
Three articles reported preclinical pharmacology of marine compounds active against the human immunodeficiency virus type-1 (HIV-1), the causative agent of the acquired immunodeficiency disease syndrome (AIDS), a decrease from our previous review [7]. Ding and colleagues investigated the novel pentacyclic indolosesquiterpene xiamycin (96) isolated from the Streptomyces sp. GT2002/1503 bacterium and demonstrated selective inhibition against macrophage and T cell β-chemokine receptor CCR5 (5) tropic HIV-infection (estimated IC 50 = 7.2 μg/mL), with no effect against α-chemokine receptor CXCR4 (X4) tropic HIV [89]. Fan and colleagues isolated several DOPA-derived pyrrole alkaloids, baculiferins I, J, L and M (97-100), from the Chinese marine sponge Iotrochota baculifera, which were found to be potent inhibitors of HIV-1 IIIB (IC 50 = 0.2-7.0 μM) by binding to the HIV target proteins Vif, APOBEC3G, and gp41 in an as yet undetermined mechanism [90]. Plaza and colleagues isolated several new cyclic depsipeptides from the Indonesian marine sponge Siliquariaspongia mirabilis including celebesides A and C (101-102), which inhibited HIV-1 in an infectivity assay (IC 50 = 1.9 ± 0.4 μg/mL), thus correlating the anti-HIV activity of these compounds with the presence of phosphoserine [57]. Table 2 presents the preclinical pharmacology of marine chemicals  which demonstrated antidiabetic and anti-inflammatory activity, as well as affected the immune and nervous system, and whose structures are shown in Figure 2.

Anti-Inflammatory Activity
There was a remarkable increase in marine anti-inflammatory pharmacology research during 2009-2011. The molecular mechanism of action of several marine natural products, which were shown in preclinical pharmacological studies to target neutrophils and macrophages both in vitro and in vivo, was reported in several publications. Asolkar and colleagues described two new cyclohexadepsipeptides arenamides A and B (105,106), isolated from the Fijian bacterium Salinispora arenicola, that inhibited LPS-induced murine macrophage RAW 264.7 cells PGE 2 and NO production in vitro, by affecting NFκB signaling activity (IC 50 = 3.7 and 1.7 μM, respectively), thus highlighting their "anti-inflammatory characteristics" [107]. Three publications yielded potentially novel compounds targeting proinflammatory mediators released by activated brain microglia, a macrophage involved in neuroinflammation and neurodegeneration [151]: Youssef and colleagues described a new steroid callysterol (107) from the Red Sea sponge Callyspongia siphonella, which potently inhibited rat hind paw edema with an activity close to cortisone, and also reduced TXB 2 release from LPS-activated rat brain microglia (apparent IC 50 > 10 μM) [108]. Jean  properties of a dermatan sulfate (115), analog of mammalian heparin, purified from the Brazilian ascidian Styela plicata, which at 8 mg/kg per day significantly decreased lymphocyte and macrophage recruitment as well as TNF-α, TGF-β, and VEGF production in the inflamed rat colon [115]. Hanif and colleagues reported that the highly hydroxylated long-chain sulfate symbiopolyol (116), isolated from a symbiotic dinoflagellate of the jellyfish Mastigias papua significantly inhibited (K 50 = 6.6 μM) the expression of the inducible adhesion vascular cell adhesion molecule-1 which binds to leukocytes present in early stages of inflammation, and thus might become a "potential anti-inflammatory agent" [116]. Costantino and colleagues reported that tedanol (117), a new brominated and sulfated pimarane diterpene isolated from the Caribbean sponge Tedania ignis, significantly reduced both the acute and subchronic phases of carrageenan-induced inflammation at 1 mg/kg with concomitant inhibition of both COX-2, iNOS expression and cellular infiltration [117].
As shown in Table 2 and in contrast to the marine anti-inflammatory compounds previously discussed, while an anti-inflammatory activity and IC 50 were reported, the molecular mechanism of action remained undetermined for the following marine compounds: carijoside A (118) [118]; chabrosterol (119)

Marine Compounds with Activity on the Immune System
In 2009-2011, immune system pharmacology of marine compounds showed a considerable decrease from our previous review. in a concentration-dependent manner (apparent IC 50 less than 20 mg/kg), suggesting HCLPS-1 might become a "potential natural immunomodulator" upon further pharmacological study [137]. Orsi and colleagues contributed to the immunopharmacology of the sulfated dinoflagellate polyether yessotoxin (148), by demonstrating that it decreased macrophage phagocytic activity against the fungus Candida albicans (apparent IC 50 = 1 nM), affected the cytoskeleton by inducing F-actin re-organization, and enhanced release of the cytokine TNF-α and chemokines MIP-1α and MIP-2 [138].

Marine Compounds Affecting the Nervous System
As shown in Table 2, the nervous system pharmacology of marine natural products in 2009-2011 involved some areas of neuropharmacology, namely neuronal neurite retraction, neurotransmission inhibition, neuronal Ca 2+ oscillations and free radical inhibition.
Marine natural products have previously been reported to affect neuritogenesis [7], a process required by neurons to respond to the extracellular environment to form synaptic connections. Inutsuka and colleagues contributed novel molecular studies on the effect of calyculin A (149) on neurons, demonstrating that rapid rat hippocampal neuron neurite retraction (apparent IC 50 = 100 mM) induced by the toxin was dependent on actin filament polymerization or myosin II motor, yet independent of the microtubule polymerization status, and perhaps resulted from dephosphorylation of myosin light chain kinase [139]. Sakurada and colleagues reported that the novel Palauan sponge Cribrochalina olemda purine (150), which elicited convulsions upon intracerebroventricular injections in mice (4 nM/mouse), inhibited GABAergic transmission in hippocampal neurons [140]. Noteworthy was the author's observation that this marine purine was "closely related in structure to endogenous neurosignaling molecules and commonly used CNS stimulants".
As shown in Table 2, two marine compounds (151,152) identified as part of a drug discovery screening program, were shown to inhibit neuronal Ca 2+ oscillations, a network phenomenon that appears to depend on voltage-gated sodium channel activation. Choi  mechanism involving free radical scavenging and reduction of mitochondrial membrane potential and superoxide generation, suggesting further development for effective stroke therapy [143].

Reviews on Marine Pharmacology
Several reviews covering both general and specific areas of marine preclinical pharmacology were published during 2009-2011: (a) marine pharmacology and marine pharmaceuticals: a renaissance in marine pharmacology: from preclinical curiosity to clinical reality [194]; biologically active marine natural products [195]; drug development from marine natural products [196]; biotechnological potential of marine natural products [197]; pharmaceuticals from marine natural products: surge or ebb? [198]; marine pharmacology in Australia: the Roche Research Institute [199]; the global marine pharmaceutical pipeline in 2010: U.S. Food and Drug Administration-approved compounds and those in Phase I, II and III of clinical development [200]; marine drugs from sponge-microbe associations [201]; cyanobacteria as an emerging source for drug discovery [202]; marine invertebrates as a future therapeutic treasure [203]; biodiversity conservation and marine natural products drug discovery [204]; marine invertebrates as a source of guanidines with chemical and pharmacological significance [205]; innovations in the field of marine natural products and a new wave of drugs [206]; (b) antimicrobial marine pharmacology: antibacterial marine natural products [207]; marine microbes and pharmaceutical development [208]; marine microbe-derived antibacterial agents [209]; antimicrobial peptides from marine invertebrates [210]; novel anti-infective compounds from marine bacteria [211]; conventional and unconventional antimicrobials from fish, marine invertebrates and microalgae [212]; (c) antiviral marine pharmacology: antiviral lead compounds from marine sponges [213]; potential anti-HIV agents from marine resources [214]; marine compounds and their antiviral activities [215]; marine organisms as a therapeutic source against herpes simplex virus infection [216]; (d) antiparasitic, antituberculosis, antimalarial and antifungal marine pharmacology: antiparasitic marine invertebrate-derived small molecules [217]; marine antileishmanial natural products [218]; antituberculosis leads from marine microbial metabolites [219]; antimalarial drug discovery from marine sources between January 2003 and December 2008 [220]; antimalarial marine natural products from 2006 to 2008 [221]; antimalarial marine compounds [222]; (e) immuno-and anti-inflammatory marine pharmacology: marine natural product leads for treatment of inflammation [223]; marine natural products targeting phospholipase A 2 [224]; marine diterpene glycosides as anti-inflammatory agents [225]; anti-inflammatory compounds from marine algae [226]; (f) cardiovascular marine pharmacology: marine-derived angiotensin-I-converting enzyme inhibitors [227]; (g) nervous system marine pharmacology: conotoxins as natural products drug leads [228]; marine indole alkaloids as new drug leads for depression and anxiety [229]; marine natural products and ion channel pharmacology [230]; neuroprotective effects of marine algae [231]; conopeptides as novel options for pain management [232]; structure-activity studies with α-conotoxins as selective antagonists of nicotinic acetylcholine receptors [233]; (h) miscellaneous molecular targets: calyculins and related marine natural products as serine threonine protein phosphatase inhibitors [234]; NF-κB inhibition by marine natural products [235]; protein kinase inhibitors from marine sponges [236].

Conclusions
The global marine preclinical and clinical pharmaceutical pipelines remain remarkably active one year after U.S. Food and Drug Administration approval of brentuximab vedotin (Adcetris ® ), a conjugate between a monoclonal antibody that targets the cell-membrane protein CD30, an antigen which is highly expressed in lymphoid tumors, and several units of the potent antimitotic agent monomethyl auristatin E, a synthetic analog of the marine compound dolastatin 10 [237].
This review aims to continue contributing to the marine preclinical pipeline review series that was initiated in 1998 [1][2][3][4][5][6][7] and reveals the breadth of preclinical pharmacological research during 2009-2011, resulting from the global research effort of chemists and pharmacologists from Australia, Belgium, Brazil, Canada, China, Colombia, Cuba, Egypt, Fiji, France, Germany, Indonesia, Israel, Italy, Japan, Luxemburg, Malaysia, Mexico, the Netherlands, New Caledonia, New Zealand, Norway, Panama, Papua New Guinea, Philippines, South Africa, South Korea, Singapore, Spain, Switzerland, Taiwan, Thailand, United Kingdom, Venezuela, Vietnam, and the United States. Thus, we feel confident to predict that the marine preclinical pharmaceutical pipeline will most probably continue to provide novel pharmacological lead compounds that will enrich the marine clinical pharmaceutical pipeline [200], which currently consists of 6 U.S. Food and Drug Administration-approved pharmaceuticals and 11 compounds in Phase I, II and III of clinical development and which may be viewed at [238].