@phdthesis{Hamm2003,
  author    = {Hamm, Andreas Peter},
  title     = {Isolierung, Strukturaufkl{\"a}rung und Totalsynthese von Naturstoffen aus tropischen Heilpflanzen und Bodenorganismen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-5461},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2003},
  abstract  = {Die Naturstoffchemie ist ein bedeutendes Teilgebiet der Chemie, da die Naturstoffe, mit ihrer breiten strukturellen Diversit{\"a}t, als neue Leitstrukturen f{\"u}r die Entwicklung spezifisch wirksamer Agrochemikalien und Arzneimittel dienen. Pflanzen und Bodenorganismen sind daher aussichtsreiche Quellen f{\"u}r neue Wirkstoffe im Bereich Pflanzenschutz- und Pharmaforschung. Aus der in der Kongo-Region beheimateten Liane Ancistrocladus ealaensis J. LEONARD (Ancistrocladaceae) wurde sieben Metabolite isoliert: Amyrin, 3,3-Di-O-methylellags{\"a}ure, zwei bisher unbekannte Naphthylisochinoline, Ancistroealain A und B, sowie drei Naphthoes{\"a}uren, die hier erstmals beschriebenen Ancistronaphthoes{\"a}uren A und B, sowie die bisher nur als Syntheseprodukt bekannte Eleutherols{\"a}ure. Ausgehend von Ancistroealain A gelang die stereoselektive Partialsynthese des bekannten Ancistrobertsonin C. Ancistroealain A zeigte in-vitro eine zehnfach h{\"o}here Aktivit{\"a}t gegen Leishmania donovani, dem Erreger der visceralen Leishmaniose, als das derzeit bei der Behandlung eingesetzte Pentostam. Um f{\"u}r In-vivo-Untersuchungen genug Material zur Verf{\"u}gung stellen zu k{\"o}nnen, wurde ein totalsynthetischer Zugang etabliert. Die Suzuki-Kupplung eines geeigneten Isochinolin-Bausteines (zehn Stufen ausgehend von 3,5-Dimethoxybenzoes{\"a}ure) mit einer Naphthalin-Borons{\"a}ure (acht Stufen ausgehend von 3-Methoxybenzaldehyd) f{\"u}hrte in einer Gesamtausbeute von 9.2 \% bzw. 6.2 \% zu dem Naturstoff. Ancistroealain A und sein Atropdiastereomer Ancitrotanzanine B, die an einer chiralen HPLC-Phase getrennt werden konnten, entstanden aufgrund der asymmetrischen Induktion durch das stereogene Zentrum C-3 in einem Verh{\"a}ltnis von 45:55. Der Ansatz einer atropselektiven Suzuki-Kupplung mit chiralem Katalysator f{\"u}hrte zu Diastereomeren{\"u}bersch{\"u}ssen bis zu 75:25. Aus Pavetta crassipes K. SCHUMANN (Rubiaceae) konnte das Phythosterol Ursols{\"a}ure isoliert werden, w{\"a}hrend aus Rothmannia urcelliformis (HIERN) BULLOCK (Rubiaceae) 1-epi-Geniposid und Gardenamid A isoliert wurde. Im Rahmen einer Kooperation mit H. Rischer gelang die Isolierung von Plumbagin, Plumbasid A und Rossolisid aus der in Neu Guinea beheimateten tropischen Kannenpflanze Nepenthis insignis DANSER. Bei Verf{\"u}tterungsexperimenten wurde (L)-[13C3,15N]-Alanin in die Kannen von sterilen Pflanzen eingebracht und ein Einbau in Plumbagin beobachtet. Die Pflanze verstoffwechselt die Aminos{\"a}uren auf den {\"u}blichen Abbauwegen und erlaubt so die Verf{\"u}tterung von Alanin als ‚maskiertes' Acetat. Das beobachtete Einbaumuster bewies die polyketidische Biosynthese von Plumbagin. In einer Kooperation mit Prof. Fiedler (T{\"u}bingen) wurden Streptomyceten aus extremen Habitaten auf die Produktion interessanter Sekund{\"a}rmetabolite untersucht und z.B. bekannte Verbindungen wie Sulfomycin I, Benzoes{\"a}ure, p-(Dimethylamino)-benzoes{\"a}ure, Juliochrome Q3-3 und Dehydrorabelomycin nachgewiesen. Der alkalophile Stamm AK 409 produzierte Pyrrol-2-carbons{\"a}ure und Pyrocoll, das im Rahmen dieser Arbeit erstmals als Naturstoff auftrat. Besonderes Interesse erregten die Antitumor-Eigenschaften von Pyrocoll. Die durchgef{\"u}hrte ‚biomimetische' Synthese von Pyrocoll ausgehend von Pyrrol-2-carbons{\"a}ure erm{\"o}glichte es uns, die f{\"u}r die In-vivo-Biotests n{\"o}tigen Substanzmengen darzustellen. Aus dem Streptomyceten AK 671 wurden eine bekannte Anthrachinoncarbons{\"a}ure und ein als Naturstoff neuartiges Diketonaphthalinglucuronid isoliert. Eine enzymatische Hydrolyse f{\"u}hrte zu dem Harris-Franck-Keton, das in dem Kulturfiltrat erstmals als Naturstoff nachgewiesen werden konnte. Das bei Verf{\"u}tterungsexperimenten mit [13C2]-Acetat von uns beobachtete Einbaumuster in das Glucuronid erlaubte die Aufkl{\"a}rung der Schl{\"u}sselschritte der Biogenese. Bei der Synthese von Naphthylisochinolinen besteht die zentrale Aufgabe in dem Aufbau der Biarylachse. Bei der Synthese von Ancistrobertsonin A nach dem ‚Lacton-Konzept' wird ein Naphtalin-Baustein mit einer zus{\"a}tzlichen C1-Einheit f{\"u}r die Esterbr{\"u}cke ben{\"o}tigt, die nach der Kupplung entfernt werden muß. Hierzu bew{\"a}hrte sich bei Versuchen an einem Modelsystem die Reaktionssequenz Baeyer-Villiger-Oxidation, Triflierung und reduktive Eliminierung. Der f{\"u}r die Synthese von Ancistrobertsonin A ben{\"o}tigte Naphthalin-Bausteines wurde in neun Stufen (Gesamtausbeute: 37 \% bzw. 13\%) dargestellt. Die Synthese des Isochinolin-Bausteines gelang in zw{\"o}lf Stufen (9.4 \%). Der Abschluß dieser Synthese ist in zuk{\"u}nftigen Arbeiten geplant.},
  subject      = {Tropische Pflanzen},
  language  = {de}
}
@article{PimentelElardoKozytskaBugnietal.2010,
  author    = {Pimentel-Elardo, Sheila Marie and Kozytska, Svitlana and Bugni, Tim S. and Ireland, Chris M. and Moll, Heidrun and Hentschel, Ute},
  title     = {Anti-Parasitic Compounds from Streptomyces sp. Strains Isolated from Mediterranean Sponges},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-68312},
  year      = {2010},
  abstract  = {Actinomycetes are prolific producers of pharmacologically important compounds accounting for about 70\% of the naturally derived antibiotics that are currently in clinical use. In this study, we report on the isolation of Streptomyces sp. strains from Mediterranean sponges, on their secondary metabolite production and on their screening for anti-infective activities. Bioassay-guided isolation and purification yielded three previously known compounds namely, cyclic depsipeptide valinomycin, indolocarbazole alkaloid staurosporine and butenolide. This is the first report of the isolation of valinomycin from a marine source. These compounds exhibited novel anti-parasitic activities specifically against Leishmania major (valinomycin IC50 < 0.11 μM; staurosporine IC50 5.30 μM) and Trypanosoma brucei brucei (valinomycin IC50 0.0032 μM; staurosporine IC50 0.022 μM; butenolide IC50 31.77 μM). These results underscore the potential of marine actinomycetes to produce bioactive compounds as well as the re-evaluation of previously known compounds for novel anti-infective activities.},
  subject      = {Biologie},
  language  = {en}
}
@article{RodriguezRicoYepesetal.2015,
  author    = {Rodriguez, H{\´e}ctor and Rico, Sergio and Yepes, Ana and Franco-Echevarr{\´i}a, Elsa and Antoraz, Sergio and Santamar{\´i}a, Ram{\´o}n I. and D{\´i}az, Margerita},
  title     = {The two kinases, AbrC1 and AbrC2, of the atypical two-component system AbrC are needed to regulate antibiotic production and differentiation in Streptomyces coelicolor},
  series = {Frontiers in Microbiology},
  volume    = {6},
  journal   = {Frontiers in Microbiology},
  number    = {450},
  doi       = {10.3389/fmicb.2015.00450},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-143048},
  year      = {2015},
  abstract  = {Two-component systems (TCSs) are the most important sensing mechanisms in bacteria. In Streptomyces, TCSs-mediated responses to environmental stimuli are involved in the regulation of antibiotic production. This study examines the individual role of two histidine kinases (HKs), AbrC1 and AbrC2, which form part of an atypical TCS in Streptomyces coelicolor. gRT-PCR analysis of the expression of both kinases demonstrated that both are expressed at similar levels in NB and NMMP media. Single deletion of abrC1 elicited a significant increase in antibiotic production, while deletion of abrC2 did not have any clear effect. The origin of this phenotype, probably related to the differential phosphorylation ability of the two kinases, was also explored indirectly, analyzing the toxic phenotypes associated with high levels of phosphorylated RR. The higher the AbrC3 regulator phosphorylation rate, the greater the cell toxicity. For the first time, the present work shows in Streptomyces the combined involvement of two different HKs in the response of a regulator to environmental signals. Regarding the possible applications of this research, the fact that an abrC1 deletion mutant overproduces three of the S. coelicolor antibiotics makes this strain an excellent candidate as a host for the heterologous production of secondary metabolites.},
  language  = {en}
}
@article{BalasubramanianOthmanKampiketal.2017,
  author    = {Balasubramanian, Srikkanth and Othman, Eman M. and Kampik, Daniel and Stopper, Helga and Hentschel, Ute and Ziebuhr, Wilma and Oelschlaeger, Tobias A. and Abdelmohsen, Usama R.},
  title     = {Marine sponge-derived Streptomyces sp SBT343 extract inhibits staphylococcal biofilm formation},
  series = {Frontiers in Microbiology},
  volume    = {8},
  journal   = {Frontiers in Microbiology},
  doi       = {10.3389/fmicb.2017.00236},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171844},
  year      = {2017},
  abstract  = {Staphylococcus epidermidis and Staphylococcus aureus are opportunistic pathogens that cause nosocomial and chronic biofilm-associated infections. Indwelling medical devices and contact lenses are ideal ecological niches for formation of staphylococcal biofilms. Bacteria within biofilms are known to display reduced susceptibilities to antimicrobials and are protected from the host immune system. High rates of acquired antibiotic resistances in staphylococci and other biofilm-forming bacteria further hamper treatment options and highlight the need for new anti-biofilm strategies. Here, we aimed to evaluate the potential of marine sponge-derived actinomycetes in inhibiting biofilm formation of several strains of S. epidermidis, S. aureus, and Pseudomonas aeruginosa. Results from in vitro biofilm-formation assays, as well as scanning electron and confocal microscopy, revealed that an organic extract derived from the marine sponge-associated bacterium Streptomyces sp. SBT343 significantly inhibited staphylococcal biofilm formation on polystyrene, glass and contact lens surfaces, without affecting bacterial growth. The extract also displayed similar antagonistic effects towards the biofilm formation of other S. epidermidis and S. aureus strains tested but had no inhibitory effects towards Pseudomonas biofilms. Interestingly the extract, at lower effective concentrations, did not exhibit cytotoxic effects on mouse fibroblast, macrophage and human corneal epithelial cell lines. Chemical analysis by High Resolution Fourier Transform Mass Spectrometry (HRMS) of the Streptomyces sp. SBT343 extract proportion revealed its chemical richness and complexity. Preliminary physico-chemical characterization of the extract highlighted the heat-stable and non-proteinaceous nature of the active component(s). The combined data suggest that the Streptomyces sp. SBT343 extract selectively inhibits staphylococcal biofilm formation without interfering with bacterial cell viability. Due to absence of cell toxicity, the extract might represent a good starting material to develop a future remedy to block staphylococcal biofilm formation on contact lenses and thereby to prevent intractable contact lens-mediated ocular infections.},
  language  = {en}
}
@phdthesis{Balasubramanian2018,
  author    = {Balasubramanian, Srikkanth},
  title     = {Novel anti-infectives against pathogenic bacteria},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-163882},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2018},
  abstract  = {Marine sponge-associated actinomycetes are reservoirs of diverse natural products with novel biological activities. Their antibiotic potential has been well explored against a range of Gram positive and negative bacteria. However, not much is known about their anti-infective or anti-virulence potential against human pathogens. This Ph.D. project aimed to investigate the anti-infective (anti-Shiga toxin and anti-biofilm) potential of sponge-derived actinobacteria through identification and isolation of their bioactive metabolites produced and characterizing their mechanism of action by transcriptomics. This thesis is divided into three studies with the overall objective of exploring the anti-infective efficacy of actinomycetes-derived extracts and compound(s) that could possibly be used as future therapeutics. The first study deals with investigation on the anti-Shiga toxin effects of sponge-associated actinomycetes. Diarrheal infections pose a huge burden in several developing and developed countries. Diarrheal outbreaks caused by Enterohemorrhagic Escherichia coli (EHEC) could lead to life-threatening complications like gastroenteritis and haemolytic uremic syndrome (HUS) if left untreated. Shiga toxin (Stx) produced by EHEC is a major virulence factor that negatively affects the human cells, leading them to death via apoptosis. Antibiotics are not prescribed against EHEC infections since they may enhance the risk of development of HUS by inducing the production and release of Stx from disintegrating bacteria and thereby, worsening the complications. Therefore, an effective drug that blocks the Stx production without affecting the growth needs to be urgently developed. In this study, the inhibitory effects of 194 extracts and several compounds originating from a collection of marine sponge-derived actinomycetes were evaluated against the Stx production in EHEC strain EDL933 with the aid of Ridascreen® Verotoxin ELISA assay kit. It was found that treatment with the extracts did not lead to significant reduction in Stx production. However, strepthonium A isolated from the culture of Streptomyces sp. SBT345 (previously cultivated from the Mediterranean sponge Agelas oroides) reduced the Stx production (at 80 μM concentration) in EHEC strain EDL933 without affecting the bacterial growth. The structure of strepthonium A was resolved by spectroscopic analyses including 1D and 2D-NMR, as well as ESI-HRMS and ESI-HRMS2 experiments. This demonstrated the possible application of strepthonium A in restraining EHEC infections. VI In the second study, the effect of marine sponge-associated actinomycetes on biofilm formation of staphylococci was assessed. Medical devices such as contact lenses, metallic implants, catheters, pacemakers etc. are ideal ecological niches for formation of bacterial biofilms, which thereby lead to device-related infections. Bacteria in biofilms are multiple fold more tolerant to the host immune responses and conventional antibiotics, and hence are hard-to-treat. Here, the anti-biofilm potential of an organic extract derived from liquid fermentation of Streptomyces sp. SBT343 (previously cultivated from the Mediterranean sponge Petrosia ficiformis) was reported. Results obtained in vitro demonstrated its anti-biofilm (against staphylococci) and non-toxic nature (against mouse macrophage (J774.1), fibroblast (NIH/3T3) and human corneal epithelial cell lines). Interestingly, SBT343 extract could inhibit staphylococcal biofilm formation on polystyrene, glass and contact lens surfaces without affecting the bacterial growth. High Resolution Fourier Transform Mass Spectrometry (HR-MS) analysis indicated the complexity and the chemical diversity of components present in the extract. Preliminary physio-chemical characterization unmasked the heat stable and non-proteinaceous nature of the active component(s) in the extract. Finally, fractionation experiments revealed that the biological activity was due to synergistic effects of multiple components present in the extract. In the third study, anti-biofilm screening of 50 organic extracts generated from solid and liquid fermentation of 25 different previously characterized sponge-derived actinomycetes was carried out. This led to identification of the anti-biofilm organic extract derived from the solid culture of Streptomyces sp. SBT348 (previously cultivated from the Mediterranean sponge Petrosia ficiformis). Bioassay-guided fractionation was employed to identify the active fraction Fr 7 in the SBT348 crude extract. Further purification with semi-preparative HPLC led to isolation of the bioactive SKC1, SKC2, SKC3, SKC4 and SKC5 sub-fractions. The most active sub-fraction SKC3 was found to be a pure compound having BIC90 and MIC values of 3.95 μg/ml and 31.25 μg/ml against S. epidermidis RP62A. SKC3 had no apparent toxicity in vitro on cell lines and in vivo on the greater wax moth Galleria melonella larvae. SKC3 was stable to heat and enzymatic treatments indicating its non-proteinaceous nature. HR-MS analysis revealed the mass of SKC3 to be 1258.3 Da. Structure elucidation of SKC3 with the aid of 1D and 2D-NMR data is currently under investigation. Further, to obtain insights into the mode of action of SKC3 on S. epidermidis RP62A, RNA sequencing was done. Transcriptome data revealed that SKC3 was recognized by RP62A at 20 min and SKC3 negatively interfered with the central metabolism of staphylococci at 3 h. Taken VII together, these findings suggest that SKC3 could be a lead structure for development of new anti-staphylococcal drugs. Overall, the results obtained from this work underscore the anti-infective attributes of actinomycetes consortia associated with marine sponges, and their applications in natural product drug discovery programs.},
  subject      = {Marine sponges},
  language  = {en}
}