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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Zanetsie Kakam, A. M.; Franke, K.; Ndom, J. C.; Dongo, E.; Mpondo, T. N.; Wessjohann, L. A.; Secondary metabolites from Helichrysum foetidum and their chemotaxonomic significance Biochem. Syst. Ecol. 39, 166-167, (2011) DOI: 10.1016/j.bse.2011.02.005

The occurrence of tetracyclic kauran type diterpenoids or related structures might be a valuable chemotaxonomic marker for further classification and subdivision of the polyphyletic genus Helichrysum.
Publikation

Yeboah, S. O.; Mitei, Y. C.; Ngila, J. C.; Wessjohann, L.; Schmidt, J.; Compositional and Structural Studies of the Major and Minor Components in Three Cameroonian Seed Oils by GC–MS, ESI-FTICR-MS and HPLC J. Am. Oil. Chem. Soc. 88, 1539-1549, (2011) DOI: 10.1007/s11746-011-1832-x

The lipid components of three Cameroonian seed oils, ke tchock (Aframomum arundinaceum), njangsa (Ricinodendron heudelotii) and calabash nutmeg (Monodora myristica), have been investigated. Gas chromatography (GC)–mass spectrometry (MS) fatty acid (FA) analysis showed M. myristica seed oil to be dominated by linoleic (49.29%) and oleic (37.17%) acids; R. heudelotii was mainly linoleic (58.73%), followed by stearic (15.00%) and oleic (14.21%) acids; A. arundinaceum was predominantly oleic (65.76%) and palmitic (20.36%) acids. Electrospray ionization (ESI)-Fourier transform ion cyclotron resonance (FTICR)-MS analysis showed seven major triacylglycerol (TAG) classes for M. myristica, with C54:5, C54:4 and C54:6 dominating. R. heudelotii had eight major TAG classes with C54:8, C54:7 and C54:6 being most abundant. A. arundinaceum also had eight major TAG classes with C52:2, C54:3 and C50:2 dominating. 13C nuclear magnetic resonance (NMR) analysis of the TAGs showed that both sn-1,3 and sn-2 positions were predominantly occupied by linoleoyl and oleoyl chains. High-performance liquid chromatography (HPLC) fluorescence detector (FLD) analysis showed that M. myristica contained only α- and β-tocopherols (195.40 and 73.95 µg/g, respectively), R. heudelotii contained mainly γ-tocopherol (289.40 µg/g), and A. arundinaceum had mainly γ- and β-tocopherols (236.78 and 124.93 µg/g, respectively). GC–MS analysis of the unsaponifiable matter showed that β-sitosterol was the most abundant phytosterol in all three seed oils. The absolute amounts of 4-desmethylsterols were 196.15, 608.71 and 362.15 µg/g for M. myristica, R. heudelotii and A. arundinaceum seed oils, respectively. These compositional and structural studies provide justification for the use of all three seed oils in food products.
Publikation

Welsch, S. J.; Umkehrer, M.; Ross, G.; Kolb, J.; Burdack, C.; Wessjohann, L. A.; PdII/IV catalyzed oxidative cyclization of 1,6-enynes derived by Ugi-4-component reaction Tetrahedron Lett. 52, 6295-6297, (2011) DOI: 10.1016/j.tetlet.2011.09.094

A variety of 1,6-enynes were synthesized by an Ugi-reaction and further elaborated by a PdII/IV catalyzed oxidative cyclization to produce N-substituted 3-aza-bicyclo[3.1.0]hexan-2-ones. Different substitution patterns were tested to examine the scope and limitations of the amide tethered substrates.
Publikation

Tarman, K.; Lindequist, U.; Wende, K.; Porzel, A.; Arnold, N.; Wessjohann, L. A.; Isolation of a New Natural Product and Cytotoxic and Antimicrobial Activities of Extracts from Fungi of Indonesian Marine Habitats Mar. Drugs 9, 294-306, (2011) DOI: 10.3390/md9030294

In the search for bioactive compounds, 11 fungal strains were isolated from Indonesian marine habitats. Ethyl acetate extracts of their culture broth were tested for cytotoxic activity against a urinary bladder carcinoma cell line and for antifungal and antibacterial activities against fish and human pathogenic bacteria as well as against plant and human pathogenic fungi. The crude extract of a sterile algicolous fungus (KT31), isolated from the red seaweed Kappaphycus alvarezii (Doty) Doty ex P.C. Silva exhibited potent cytotoxic activity with an IC50 value of 1.5 µg/mL. Another fungal strain (KT29) displayed fungicidal properties against the plant pathogenic fungus Cladosporium cucumerinum Ell. et Arth. at 50 µg/spot. 2-Carboxy-8-methoxy-naphthalene-1-ol (1) could be isolated as a new natural product.
Publikation

Schneider, T.; Ba, L. A.; Khairan, K.; Zwergel, C.; Bach, N. D.; Bernhardt, I.; Brandt, W.; Wessjohann, L.; Diederich, M.; Jacob, C.; Interactions of polysulfanes with components of red blood cells Med. Chem. Commun. 2, 196-200, (2011) DOI: 10.1039/C0MD00203H

Traditionally, the activity of most polysulfanes has been associated with the redox behaviour of the sulfur-sulfur bond. Here we show that polysulfanes, such as diallyltri- and tetrasulfide, also interact with cellular membranes and certain metalloproteins. Together, multiple interactions with various biological targets may explain best the biological activity of such compounds.
Publikation

Ruela, H. S.; Leal, I. C. R.; de Almeida, M. R. A.; dos Santos, K. R. N.; Wessjohann, L. A.; Kuster, R. M.; Antibacterial and antioxidant activities and acute toxicity of Bumelia sartorum Mart., Sapotaceae, a Brazilian medicinal plant Rev. Bras. Farmacogn. 21, 86-91, (2011) DOI: 10.1590/S0102-695X2011005000035

In order to validate the Bumelia sartorum Mart., Sapotaceae, traditional use for infection diseases, this study evaluates the antibacterial activity of the stem bark fractions against methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus strains by using the agar dilution method and reported as MIC (minimal inhibitory concentration). In addition, the DPPH scavenging activity of these fractions was measured and the chemical composition and acute toxicity of the active fraction were also determined. The ethyl acetate (EtOAc) extract was chemically analyzed by LC/MS, direct ionization APCI/MS, 1H NMR and 13C-NMR. All fractions, except butanol extract, presented high antioxidant activity, especially the methanol and the EtOAc extracts, which showed EC50 values (5.67 and 5.30 µg/mL, respectively) considerably lower than the Gingko-standard EGb 761® (38.58 µg/mL). The antibacterial activity against S. aureus strains was observed in EtOAc (MIC 256-512 µg/mL), which showed a very low toxicity. The chemical study of this fraction revealed the abundant presence of polyphenolic compounds. The antibacterial and antioxidant activities reported in this paper for EtOAc extract from B. sartorum and the low toxicity of this fraction opens the possibility that it could be helpful for the developing of new antibacterial agents for treating S. aureus infections.
Publikation

Rodríguez-Díaz, M.; Delporte, C.; Cartagena, C.; Cassels, B. K.; González, P.; Silva, X.; León, F.; Wessjohann, L. A.; Topical anti-inflammatory activity of quillaic acid from Quillaja saponaria Mol. and some derivatives J. Pharm. Pharmacol. 63, 718-724, (2011) DOI: 10.1111/j.2042-7158.2011.01263.x

Objectives Quillaic acid is the major aglycone of the widely studied saponins of the Chilean indigenous tree Quillaja saponaria Mol. The industrial availability of quillaja saponins and the extensive functionalisation of this triterpenoid provide unique opportunities for structural modification and pose a challenge from the standpoint of selectivity in regard to one or the other secondary alcohol group, the aldehyde, and the carboxylic acid functions. The anti‐inflammatory activity of this sapogenin has not been studied previously and it has never been used to obtain potential anti‐inflammatory derivatives.Methods A series of quillaic acid derivatives were prepared and subjected to topical assays for the inhibition of inflammation induced by arachidonic acid or phorbol ester.Key findings Quillaic acid exhibited strong topical anti‐inflammatory activity in both models. Most of its derivatives were less potent, but the hydrazone 8 showed similar potency to quillaic acid in the TPA assay.Conclusions The structural modifications performed and the biological results suggest that the aldehyde and carboxyl groups are relevant to the anti‐inflammatory activity in these models.
Publikation

Rashan, L. J.; Franke, K.; Khine, M. M.; Kelter, G.; Fiebig, H. H.; Neumann, J.; Wessjohann, L. A.; Characterization of the anticancer properties of monoglycosidic cardenolides isolated from Nerium oleander and Streptocaulon tomentosum J. Ethnopharmacol. 134, 781-788, (2011) DOI: 10.1016/j.jep.2011.01.038

Aim of the studyFor identification of the active constituents we investigated the anticancer activity of cardenolides from Streptocaulon tomentosum Wight & Arn. (Asclepiadaceae) and from Nerium oleander L. (Apocynaceae) which are both used against cancer in the traditional medicine in their region of origin.Material, methods and resultsThe antiproliferative activity of cardenolides isolated from roots of Streptocaulon tomentosum (IC50 < 1–15.3 μM after 2 days in MCF7) and of cardenolide containing fractions from the cold aqueous extract of Nerium oleander leaves (“Breastin”, mean IC50 0.85 μg/ml in a panel of 36 human tumor cell lines), their influence on the cellular viability and on the cell cycle (block at the G2/M-phase or at the S-phase in tumor cells, respectively) were determined using different cell lines. The murine cell line L929 and normal non-tumor cells were not affected. Bioactivity guided fractionation of Breastin resulted in the isolation of the monoglycosidic cardenolides oleandrine, oleandrigeninsarmentoside, neritaloside, odoroside H, and odoroside A (IC50-values between 0.010 and 0.071 μg/ml).ConclusionsThe observed anticancer activities of extracts and isolated cardenolides are in agreement with the ethnomedicinal use of Streptocaulon tomentosum and Nerium oleander. The most active anticancer compounds from both species are monoglycosidic cardenolides possessing the 3β,14β-dihydroxy-5β-card-20(22)-enolide structure with or without an acetoxy group at C-16. The results indicate that the cytotoxic effects are induced by the inhibition of the plasma membrane bound Na+/K+-ATPase.
Publikation

Pando, O.; Stark, S.; Denkert, A.; Porzel, A.; Preusentanz, R.; Wessjohann, L. A.; The Multiple Multicomponent Approach to Natural Product Mimics: Tubugis, N-Substituted Anticancer Peptides with Picomolar Activity J. Am. Chem. Soc. 133, 7692-7695, (2011) DOI: 10.1021/ja2022027

The synthesis of a new generation of highly cytotoxic tubulysin analogues (i.e., tubugis) is described. In the key step, the rare, unstable, and synthetically difficult to introduce tertiary amide–N,O-acetal moiety required for high potency in natural tubulysins is replaced by a dipeptoid element formed in an Ugi four-component reaction. Two of the four components required are themselves produced by other multicomponent reactions (MCRs). Thus, the tubugis represent the first examples of the synthesis of natural-product-inspired compounds using three intertwined isonitrile MCRs.
Publikation

Neves Filho, R. A. W.; Westermann, B.; Wessjohann, L. A.; Synthesis of (−)-julocrotine and a diversity oriented Ugi-approach to analogues and probes Beilstein J. Org. Chem. 7, 1504-1507, (2011) DOI: 10.3762/bjoc.7.175

An improved total synthesis of (−)-julocrotine in three steps from Cbz-glutamine, in 51% overall yield, is presented. To demonstrate the potential of the heterocyclic moiety for diversity oriented synthesis, a series of (−)-julocrotine analogues was synthesized by employing the heterocyclic precursor as an amino input in Ugi four-component reactions (Ugi-4CR) [1].
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