Current Approaches to Discover Marine Antileishmanial Natural Products

Abstract

Leishmaniasis is a neglected infectious disease caused by kinetoplastid protozoans. An urgent need for novel chemotherapeutics exists. The current approaches to discover new antileishmanial compounds present many drawbacks, including high-cost and time-consuming bioassays. Thus, advances in leishmaniasis treatment are limited, and the development of screening assays is hindered. The combination of multidisciplinary approaches using standardised methods and synchronous projects could be an alternative to develop novel drugs for leishmaniasis treatment. In this review, we discuss the current status of leishmaniasis occurrence and treatment. In addition, we address the advantages and limitations of in vitro leishmaniasis bioassays and discuss the findings of drug discovery research using natural products. Finally, we comprehensively review the marine natural products that are active against Leishmania spp., including their natural sources and bioactivity profile.

Key words

leishmaniasis - drug - therapy - marine natural products - in vitro bioassays - Leishmania

References

• 1 World Health Organization .Leishmaniasis. http://www.who.int/leishmaniasis/en/ Accessed November 22, 2010
• 2 Croft S L, Sundar S, Fairlamb A H. Drug resistance in leishmaniasis.  Clin Microbiol Rev. 2006;  19 111-126
• 3 Janvier F, Morillon M, Olliaro P. Visceral leishmaniasis: clinical sensitivity and resistance to various therapeutic agents.  Med Trop Mars. 2008;  68 89-101
• 4 Lukes J, Mauricio I L, Schonian G, Dujardin J C, Soteriadou K, Dedet J P, Kuhis K, Tintaya K W, Jirku M, Chocholova E, Haralambous C, Prationg F, Obornik M, Horak A, Ayala F J, Miles M A. Evolutionary and geographical history of the Leishmania donovani complex with a revision of current taxonomy.  Proc Natl Acad Sci USA. 2007;  104 9375-9380
• 5 Mauricio I L, Stothard J R, Miles M A. The strange case of Leishmania chagasi.  Parasitol Today. 2000;  16 188-189
• 6 Berman J. Visceral leishmaniasis in the New World & Africa.  Indian J Med Res. 2006;  123 289-294
• 7 Lindoso J A, Lindoso A A. Neglected tropical diseases in Brazil.  Rev Inst Med Trop Sao Paulo. 2009;  51 247-253
• 8 Rittig M G, Bogdan C. Leishmania–interaction: complexities and alternative views.  Parasitol Today. 2000;  16 292-297
• 9 Mishra B B, Singh R K, Srivastava A, Tripathi V J, Tiwari V K. Fighting against Leishmaniasis: search of alkaloids as future true potential anti-Leishmanial agents.  Mini Rev Med Chem. 2009;  9 107-123
• 10 Frézard F, Demicheli C, Ribeiro R R. Pentavalent antimonials: new perspectives for old drugs.  Molecules. 2009;  30 2317-2336
• 11 Mishra J, Saxena A, Singh S. Chemotherapy of leishmaniasis: past, present and future.  Curr Med Chem. 2007;  14 1153-1169
• 12 Sundar S. Drug resistance in Indian visceral leishmaniasis.  Trop Med Int Health. 2001;  6 849-854
• 13 Sundar S, Chatterjee M. Visceral leishmaniasis – current therapeutic modalities.  Indian J Med Res. 2006;  123 345-352
• 14 Sundar S, Rosenkaimer F, Makharia M K, Goyal A K, Mandal A K, Voss A, Hilgard P, Murray H W. Trial of oral miltefosine for visceral leishmaniasis.  Lancet. 1998;  352 1821-1823
• 15 van Griensven J, Balasegaram M, Meheus F, Alvar J, Lynen L, Boelaert M. Combination therapy for visceral leishmaniasis.  Lancet Infect Dis. 2010;  10 184-194
• 16 Sundar S, Rai M, Chakravarty J, Agarwal D, Agrawal N, Vaillant M, Olliaro P, Murray H W. New treatment approach in Indian visceral leishmaniasis: single-dose liposomal amphotericin B followed by short-course oral miltefosine.  Clin Infect Dis. 2008;  47 1000-1006
• 17 Bhattacharya S K, Sinha P K, Sundar S, Thakur C P, Jha T K, Pandey K, Das V R, Kumar N, Lal C, Verma N, Singh V P, Ranjan A, Verma R B, Anders G, Sindermann H, Ganguly N K. Phase IV trial of miltefosine in the treatment of Indian visceral leishmaniasis.  J Infect Dis. 2007;  196 591-598
• 18 Soto J, Arana B A, Toledo J, Rizzo N, Vega J C, Diaz A. Miltefosine for new world cutaneous leishmaniasis.  Clin Infect Dis. 2004;  38 1266-1272
• 19 Bryceson A. A policy for leishmaniasis with respect to the prevention and control of drug resistance.  Trop Med Int Health. 2001;  6 928-934
• 20 Chappuis F, Sundar S, Hailu A, Ghalib H, Rijal S, Peeling R W, Alvar J, Boelaert M. Visceral leishmaniasis: what are the needs for diagnosis, treatment and control?.  Nat Rev Microbiol. 2007;  5 873-882
• 21 Jha T K, Olliaro P, Thakur C P, Kanyok T P, Singhania B L, Singh N K, Akhoury S, Jha S. Randomised controlled trial of aminosidine (paromomycin) v sodium stibogluconate for treating visceral leishmaniasis in North Bihar, India.  BMJ. 1998;  316 1200-1205
• 22 Coimbra E S, Libong D, Cojean S, Saint-Pierre-Chazalet M, Solgadi A, Le Moyec L, Duenas-Romero A M, Chaminade P, Loiseau P M. Mechanism of interaction of sitamaquine with Leishmania donovani.  J Antimicrob Chemother. 2010;  65 2548-2555
• 23 Dietze R, Carvalho S F, Valli L C, Berman J, Brewer T, Milhous W, Sanchez J, Schuster B, Grogl M. Phase 2 trial of WR6026, an orally administered 8-aminoquinoline, in the treatment of visceral leishmaniasis caused by Leishmania chagasi.  Am J Trop Med Hyg. 2001;  65 685-689
• 24 Jha T K, Sundar S, Thakur C P, Felton J M, Sabin A J, Horton J. A phase II dose-ranging study of sitamaquine for the treatment of visceral leishmaniasis in India.  Am J Trop Med Hyg. 2005;  73 1005-1011
• 25 Lima E B. Tratamento da leishmaniose tegumentar Americana.  An Bras Dermatol. 2007;  82 111-124
• 26 Grecco S S, Reimão J Q, Tempone A G, Sartorelli P, Romoff P, Ferreira M J, Fávero O A, Lago J H. Isolation of an antileishmanial and antitrypanosomal flavanone from the leaves of Baccharis retusa DC. (Asteraceae).  Parasitol Res. 2010;  106 1245-1248
• 27 Tempone A G, Sartorelli P, Teixeira D, Prado F O, Calixto I A, Lorenzi H, Melhem M S. Brazilian flora extracts as source of novel antileishmanial and antifungal compounds.  Mem Inst Oswaldo Cruz. 2008;  103 443-449
• 28 Tempone A G, Pimenta D C, Lebrun I, Sartorelli P, Taniwaki N N, de Andrade Jr H F, Antoniazzi M M, Jared C. Antileishmanial and antitrypanosomal activity of bufadienolides isolated from the toad Rhinella jimi parotoid macrogland secretion.  Toxicon. 2008;  52 13-21
• 29 Muzitano M F, Falcão C A, Cruz E A, Bergonzi M C, Bilia A R, Vincieri F F, Rossi-Bergmann B, Costa S S. Oral metabolism and efficacy of Kalanchoe pinnata flavonoids in a murine model of cutaneous leishmaniasis.  Planta Med. 2009;  75 307-311
• 30 Copp B R, Kayser O, Brun R, Kiderlen A F. Antiparasitic activity of marine pyridoacridone alkaloids related to the ascididemins.  Planta Med. 2003;  69 527-531
• 31 Tada H, Shiho O, Kuroshima K, Koyama M, Tsukamoto K. An improved colorimetric assay for interleukin 2.  J Immunol Methods. 1986;  93 157-165
• 32 Ganguly S, Bandyopadhyay S, Sarkar A, Chatterjee M. Development of a semiautomated colorimetric assay for screening anti-leishmanial agents.  J Microbiol Methods. 2005;  66 78-86
• 33 Sereno D, Lemesre J L. Axenically cultured amastigote forms as an in vitro model for investigation of antileishmanial agents.  Antimicrob Agents Chemother. 1997;  41 972-976
• 34 Mikus J, Steverding D. A simple colorimetric method to screen drug cytotoxicity against Leishmania using the dye Alamar Blue.  Parasitol Int. 2000;  48 265-269
• 35 Callahan H L, Portal A C, Devereaux R, Grögl M. An axenic amastigotesystem for drug screening.  Antimicrob Agents Chemother. 1997;  41 818-822
• 36 Ephros M, Waldman E, Zilberstein D. Pentostam induces resistance to antimony and the preservative chlorocresol in Leishmania donovani promastigotes and axenically grown amastigotes.  Antimicrob Agents Chemother. 1997;  41 1064-1068
• 37 Sereno D, Alegre A M, Silvestre R, Vergnes B, Ouaissi A. In vitro antileishmanial activity of nicotinamide.  Antimicrob Agents Chemother. 2005;  49 808-812
• 38 Vergnes B, Vanhille L, Ouaissi A, Sereno D. Stage-specific antileishmanial activity of an inhibitor of SIR2 histone deacetylase.  Acta Trop. 2005;  94 107-115
• 39 Sereno D, Cordeiro da Silva A, Mathieu-Daude F, Ouaissi A. Advances and perspectives in Leishmania cell based drug-screening procedures.  Parasitol Int. 2007;  56 3-7
• 40 Seifert K, Escobar P, Croft S L. In vitro activity of anti-leishmanial drugs against Leishmania donovani is host cell dependent.  J Antimicrob Chemother. 2010;  65 508-511
• 41 Kram D, Thäle C, Kolodziej H, Kiderlen A F. Intracellular parasite kill: flow cytometry and NO detection for rapid discrimination between anti-leishmanial activity and macrophage activation.  J Immunol Methods. 2008;  20 79-88
• 42 Wanderley J L, Benjamin A, Real F, Bonomo A, Moreira M E, Barcinski M A. Apoptotic mimicry: an altruistic behavior in host/Leishmania interplay.  Braz J Med Biol Res. 2005;  38 807-812
• 43 de Freitas Balanco J M, Moreira M E, Bonomo A, Bozza P T, Amarante-Mendes G, Pirmez C, Barcinski M A. Apoptotic mimicry by an obligate intracellular parasite downregulates macrophage microbicidal activity.  Curr Biol. 2001;  27 1870-1873
• 44 Giudice A, Camada I, Leopoldo P T, Pereira J M, Riley L W, Wilson M E, Ho J L, de Jesus A R, Carvalho E M, Almeida R P. Resistance of Leishmania (Leishmania) amazonensis and Leishmania (Viannia) braziliensis to nitric oxide correlates with disease severity in Tegumentary Leishmaniasis.  BMC Infect Dis. 2007;  22 7-10
• 45 Morais-Teixeira E, Carvalho A S, Costa J C, Duarte S L, Mendonça J S, Boechat N, Rabello A. In vitro and in vivo activity of meglumine antimoniate produced at Farmanguinhos-Fiocruz, Brazil, against Leishmania (Leishmania) amazonensis, L (L.) chagasi and L (Viannia) braziliensis.  Mem Inst Oswaldo Cruz. 2008;  103 358-362
• 46 Collins L A, Torrero M N, Franzblau S G. Green fluorescent protein reporter microplate assay for high-throughput screening of compounds against Mycobacterium tuberculosis.  Antimicrob Agents Chemother. 1998;  42 344-347
• 47 Jacobs Jr W R, Barletta R G, Udani R, Chan J, Kalkut G, Sosne G, Kieser T, Sarkis G J, Hatfull G F, Bloom B R. Rapid assessment of drug susceptibilities of Mycobacterium tuberculosis by means of luciferase reporter phages.  Science. 1993;  260 819-822
• 48 Buckner F S, Verlinde C L, La Flamme A C, Van Voorhis W C. Efficient technique for screening drugs for activity against Trypanosoma cruzi using parasites expressing β-galactosidase.  Antimicrob Agents Chemother. 1996;  40 2592-2597
• 49 Mc Fadden D C, Seeber F, Boothroyd J C. Use of Toxoplasma gondii expressing β-galactosidase for colorimetric assessment of drug activity in vitro.  Antimicrob Agents Chemother. 1997;  41 1849-1853
• 50 Naylor L H. Reporter gene technology: the future looks bright.  Biochem Pharmacol. 1999;  58 749-757
• 51 Lang T, Goyard S, Lebastard M, Milon G. Bioluminescent Leishmania expressing luciferase for rapid and high throughput screening of drugs acting on amastigote-harbouring macrophages and for quantitative real-time monitoring of parasitism features in living mice.  Cell Microbiol. 2005;  7 383-392
• 52 Dube A, Gupta R, Singh N. Reporter genes facilitating discovery of drugs targeting protozoan parasites.  Trends Parasitol. 2009;  25 432-439
• 53 Tsien R Y. Green fluorescent protein.  Annu Rev Biochem. 1998;  67 509-544
• 54 Kain S R. Green fluorescent protein (GFP): applications in cell-based assays for drug discovery.  Drug Discov Today. 1999;  4 304-312
• 55 Singh N, Dube A. Fluorescent Leishmania: applications to antileishmanial drug testing.  Am J Trop Med Hyg. 2004;  71 400-402
• 56 Okuno T, Goto Y, Matsumoto Y, Otsuka H, Matsumoto Y. Applications of recombinant Leishmania amazonensis expressing egfp or the betagalactosidase gene for drug screening and histopathological analysis.  Exp Anim. 2003;  52 109-118
• 57 Campbell R E. Realization of β-lactamase as a versatile fluorogenic reporter.  Trends Biotechnol. 2005;  22 208-211
• 58 Buckner F S, Wilson A J. Colorimetric assay for screening compounds against Leishmania amastigotes grown in macrophages.  Am J Trop Med Hyg. 2005;  72 600-605
• 59 Sutcliffe J G. Nucleotide sequence of the ampicillin resistance gene of Escherichia coli plasmid pBR322.  Proc Natl Acad Sci USA. 1978;  75 3737-3741
• 60 Moore J T, Davis S T, Dev I K. The development of betalactamase as a highly versatile genetic reporter for eukaryotic cells.  Anal Biochem. 1997;  247 203-209
• 61 Messaritakis I, Mazeris A, Koutala E, Antoniou M. Leishmania donovani s.l.: evaluation of the proliferation potential of promastigotes using CFSE stainin and flow cytometry.  Exp Parasitol. 2010;  125 384-388
• 62 Garner D L, Johnson L A, Yue S T, Roth B L, Haugland R P. Dual DNA staining assessment of bovine sperm viability using SYBR-14 and propidium iodide.  J Androl. 1994;  15 620-629
• 63 Abdullah S M, Flath B, Presber H W. Comparison of different staining procedures for the flow cytometric analysis of U-937 cells infected with different Leishmania-species.  J Microbiol Methods. 1999;  37 123-138
• 64 Handman E, Spira D T. Growth of Leishmania amastigotes in macrophages from normal and immune mice.  Z Parasitenkd. 1977;  25 75-81
• 65 Ghosh A K, Bhattacharyya F K, Ghosh D K. Leishmania donovani: amastigote inhibition and mode of action of berberine.  Exp Parasitol. 1985;  60 404-413
• 66 Bodley A L, McGarry M W, Shapiro T A. Drug cytotoxicity assay for African trypanosomes and Leishmania species.  J Infect Dis. 1995;  172 1157-1159
• 67 Macarron R. Critical review of the role of HTS in drug discovery.  Drug Discov Today. 2006;  11 277-279
• 68 Mayr L M, Bojanic D. Novel trends in high-throughput screening.  Curr Opin Pharmacol. 2009;  9 580-588
• 69 Croft S L, Coombs G H. Leishmaniasis–current chemotherapy and recent advances in the search for novel drugs.  Trends Parasitol. 2003;  19 502-508
• 70 Lackovic K, Parisot J P, Sleebs N, Baell J B, Debien L, Watson K G, Curtis J M, Handman E, Street I P, Kedzierski L. Inhibitors of Leishmania GDP-mannose pyrophosphorylase identified by high-throughput screening of small-molecule chemical library.  Antimicrob Agents Chemother. 2010;  54 1712-1719
• 71 Blunt J W, Copp B R, Munro M H G, Northcote P T, Prinsep M R. Marine natural products.  Nat Prod Rep. 2010;  27 165-237
• 72 Sanchez L M, Lopez D, Vesely B A, Togna G T, Gerwick W H, Kyle D E, Linington R G. Almiramides A–C: discovery and development of a new class of Leishmaniasis lead compounds.  J Med Chem. 2010;  53 4187-4197
• 73 Balunas M J, Linington R G, Tidgewell K, Fenner A M, Ureña L D, Togna G D, Kyle D E, Gerwick W H. Dragonamide E, a modified linear lipopeptide from Lyngbya majuscula with antileishmanial activity.  J Nat Prod. 2010;  73 60-66
• 74 Simmons T L, Engene N, Ureña L D, Romero L I, Ortega-Barría E, Gerwick L, Gerwick W H. Viridamides A and B, lipodepsipeptides with antiprotozoal activity from the marine cyanobacterium Oscillatoria nigro-wiridis.  J Nat Prod. 2008;  71 1544-1550
• 75 Linington R G, Benjamin R C, Trimble E E, Almanza A, Ureña L D, Kyle D E, Gerwick W H. Antimalarial peptides from marine cyanobacteria: isolation and structural elucidation of gallinamide A.  J Nat Prod. 2009;  72 14-17
• 76 Cruz L J, Luque-Ortega J R, Rivas L, Albericio F. Kahalalide F, an antitumor depsipeptide in clinical trials, and its analogues as effective antileishmanial agents.  Mol Pharm. 2009;  6 813-824
• 77 Nakao Y, Kawatsu S, Okamoto C, Okamoto M, Matsumoto Y, Matsunaga S, van Soest R W, Fusetani N. Ciliatamides A–C, bioactive lipopeptides from the deep-sea sponge Aaptos ciliata.  J Nat Prod. 2008;  71 469-472
• 78 Pimentel-Elardo S M, Kozytska S, Bugni T S, Ireland C M, Moll H, Hentschel U. Anti-parasitic compounds from Streptomyces sp. strains isolated from Mediterranean sponges.  Mar Drugs. 2010;  8 373-380
• 79 Linington R G, Edwards D J, Shuman C F, McPhail K L, Matainaho T, Gerwick W H. Symplocamide A, a potent cytotoxin and chymotrypsin inhibitor from the marine cyanobacterium Symploca sp.  J Nat Prod. 2008;  71 22-27
• 80 Linington R G, González J, Ureña L D, Romero L I, Ortega-Barría E, Gerwick W H. Venturamides A and B: antimalarial constituents of the Panamanian marine cyanobacterium Oscillatoria sp.  J Nat Prod. 2007;  70 397-401
• 81 Le Pape P, Zidane M, Abdala H, Moré M T. A glycoprotein isolated from the sponge, Pachymatisma johnstonii, has anti-leishmanial activity.  Cell Biol Int. 2000;  24 51-56
• 82 Orhan I, Şener B, Kaiser M, Brun R, Tasdemir D. Inhibitory activity of marine sponge-derived natural products against parasitic protozoa.  Mar Drugs. 2010;  8 47-58
• 83 Gul W, Hammond N L, Yousaf M, Peng J, Holley A, Hamann M T. Chemical transformation and biological studies of marine sesquiterpene (S)-(+)-curcuphenol and its analogs.  Biochim Biophys Acta. 2007;  1770 1513-1519
• 84 Singh N, Kumar R, Gupta S, Dube A, Lakshmi V. Antileishmanial activity “in vitro” and “in vivo” of constituents of sea cucumber Actinopyga lecanora.  Parasitol Res. 2008;  103 351-354
• 85 Regalado E L, Tasdemir D, Kaiser M, Cachet N, Amade P, Thomas O P. Antiprotozoal steroidal saponins from the marine sponge Pandaros acanthifolium.  J Nat Prod. 2010;  73 1404-1410
• 86 Gray C A, Lira S P, Silva M, Pimenta E F, Thiemann O H, Oliva G O, Hajdu E, Andersen R J, Berlinck R G S. Sulfated meroterpenoids from the Brazilian sponge Callyspongia sp. are inhibitors of the antileishmaniasis target adenosine phosphoribosyl transferase.  J Org Chem. 2006;  71 8685-8690
• 87 Savoia D, Avanzini C, Allice T, Callone E, Guella G, Dini F. Antimicrobial activity of euplotin c, the sesquiterpene taxonomic marker from the marine ciliate Euplotes crassus.  Antimicrob Agents Chemother. 2004;  48 3828-3833
• 88 Rangel H R, Dagger F, Compagnone R S. Antiproliferative effect of illimaquinone on Leishmania mexicana.  Cell Biol Int. 1997;  21 337-339
• 89 Dube A, Singh N, Saxena A, Lakshmi V. Antileishmanial potential of a marine sponge, Haliclona exigua (Kirkpatrick) against experimental visceral leishmaniasis.  Parasitol Res. 2007;  101 317-324
• 90 Mishra B B, Singh R K, Srivastava A, Tripathi V J, Tiwari V K. Fighting against leishmaniasis: search of alkaloids as future true potential anti-leishmanial agents.  Med Chem. 2009;  9 107-123
• 91 Hua H M, Peng J, Fronczek F R, Kelly M, Hamann M T. Crystallographic and NMR studies of antiinfective tricyclic guanidine alkaloids from the sponge Monanchora unguifera.  Bioorg Med Chem. 2004;  12 6461-6464
• 92 Nakao Y, Shiroiwa T, Murayama S, Matsunaga S, Goto Y, Matsumoto Y, Fusetani N. Identification of renieramycin a as an antileishmanial substance in a marine sponge Neopetrosia sp.  Mar Drugs. 2004;  2 55-62
• 93 Copp B R, Kayser O, Brun R, Kiderlen A F. Antiparasitic activity of marine pyridoacridone alkaloids related to the ascididemins.  Planta Med. 2003;  69 527-531
• 94 Gul G, Hammond N L, Yousaf M, Bowling J J, Schinazi R F, Wirtz S S, Andrews G C, Cuevas C, Hamann M T. Modification at the C9 position of the marine natural product isoaaptamine and the impact on HIV-1, mycobacterial, and tumor cell activity.  Bioorg Med Chem. 2006;  14 8495-8505
• 95 Rao K V, Donia M S, Peng J, Garcia-Palomero E, Alonso D, Martinez A, Medina M, Franzblau S G, Tekwani B L, Khan S I, Wahyuono S, Willett K L, Hamann M T. Manzamine B and E and ircinal a related alkaloids from an indonesian Acanthostrongylophora sponge and their activity against infectious, tropical parasitic, and Alzheimer's diseases.  J Nat Prod. 2006;  69 1034-1040
• 96 Shilabin A G, Kasanah N, Tekwani B L, Hamann M T. Kinetic studies and bioactivity of potential manzamine prodrugs.  J Nat Prod. 2008;  71 1218-1221
• 97 Rao K V, Kasanah N, Wahyuono S, Tekwani B L, Schinazi R F, Hamann M T. Three new manzamine alkaloids from a common Indonesian sponge and their activity against infectious and tropical parasitic diseases.  J Nat Prod. 2004;  67 1314-1318
• 98 Rao K V, Santarsiero B D, Mesecar A D, Schinazi R F, Tekwani B L, Hamann M T. New manzamine alkaloids with activity against infectious and tropical parasitic diseases from an Indonesian sponge.  J Nat Prod. 2003;  66 823-828
• 99 Scala F, Fattorusso E, Menna M, Taglialatela-Scafati O, Tierney M, Kaiser M, Tasdemir D. Bromopyrrole alkaloids as lead compounds against protozoan parasites.  Mar Drugs. 2010;  8 2162-2174
• 100 Giddens A C, Nielsen L, Boshoff H I, Tasdemir D, Perozzo R, Kaiser M, Wang F, Sacchettini J C, Copp B R. Natural product inhibitors of fatty acid biosynthesis: synthesis of the marine microbial metabolites pseudopyronines A and B and evaluation of their anti-infective activities.  Tetrahedron. 2008;  64 1242-1249
• 101 Kossuga M H, Nascimento A M, Reimão J Q, Tempone A G, Taniwaki N N, Veloso K, Ferreira A G, Cavalcanti B C, Pessoa C, Moraes M O, Mayer M A S, Hajdu E, Berlinck R G S. Antiparasitic, antineuroinflammatory, and cytotoxic polyketides from the marine sponge Plakortis angulospiculatus collected in Brazil.  J Nat Prod. 2008;  71 334-339
• 102 Compagnone R S, Piña I C. Antileishmanial cyclic peroxides from the Palauan sponge Plakortis aff. angulospiculatus.  Tetrahedron. 1998;  54 3057-3068
• 103 Ueoka R, Nakao Y, Kawatsu S, Yaegashi J, Matsumoto Y, Matsunaga S, Furihata K, van Soest R W, Fusetani N. Gracilioethers A–C, antimalarial metabolites from the marine sponge Agelas gracilis.  J Org Chem. 2009;  74 4203-4207
• 104 Pontius A, Krick A, Kehraus S, Brun R, Konig G M. Antiprotozoal activities of heterocyclic-substituted xanthones from the marine-derived fungus Chaetomium sp.  J Nat Prod. 2008;  71 1579-1584
• 105 Vik A, Proszenyák A, Vermeersch M, Cos P, Maes L, Gundersen L L. Screening of agelasine D and analogs for inhibitory activity against pathogenic protozoa; identification of hits for visceral leishmaniasis and chagas disease.  Molecules. 2009;  14 279-288
• 106 Kossuga M H, Lira S P, Nascimento A M, Gambardella M T P, Berlinck R G S, Torres Y R, Nascimento G F F, Pimenta E F, Silva M, Thiemann O, Oliva G, Tempone A, Melhem M S C, Souza A O. Isolamento e atividades biológicas de produtos naturais das esponjas Monanchora arbuscula, Aplysina sp., Petromica ciocalyptoides e Topsentia ophiraphidites, da ascídia Didemnum ligulum e do octocoral Carijoa riisei.  QN. 2007;  30 1194-1202
• 107 Tasdemir D, Topaloglu B, Perozzo R, Brun R, O'Neill R, Carballeira N M, Zhang X, Tonge P J, Linden A, Ruedi P. Marine natural products from the Turkish sponge Agelas oroides that inhibit the enoyl reductases from Plasmodium falciparum, Mycobacterium tuberculosis and Escherichia coli.  Bioorg Med Chem. 2007;  15 6834-6845
• 108 Ma W S, Mutka T, Vesley B, Amsler M O, McClintock J B, Amsler C D, Perman J A, Singh M P, Maiese W M, Zaworotko M J, Kyle D E, Baker B J. Norselic acids A–E, highly oxidized anti-infective steroids that deter mesograzer predation, from the Antarctic sponge Crella sp.  J Nat Prod. 2009;  72 1842-1846