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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Fobofou, S. A. T.; Franke, K.; Brandt, W.; Manzin, A.; Madeddu, S.; Serreli, G.; Sanna, G.; Wessjohann, L. A.; Bichromonol, a dimeric coumarin with anti-HIV activity from the stem bark of Hypericum roeperianum Nat. Prod. Res. 37, 1947-1953, (2023) DOI: 10.1080/14786419.2022.2110094

Infectious diseases caused by viruses like HIV and SARS-COV-2 (COVID-19) pose serious public health threats. In search for new antiviral small molecules from chemically underexplored Hypericum species, a previously undescribed atropisomeric C8-C8’ linked dimeric coumarin named bichromonol (1) was isolated from the stem bark of Hypericum roeperianum. The structure was elucidated by MS data and NMR spectroscopy. The absolute configuration at the biaryl axis was determined by comparing the experimental ECD spectrum with those calculated for the respective atropisomers. Bichromonol was tested in cell-based assays for cytotoxicity against MT-4 (CC50 ¼ 54 mM) cells and anti-HIV activity in infected MT-4 cells. It exhibits significant activity at EC50 ¼ 6.6–12.0 mM against HIV-1 wild type and its clinically relevant mutant strains. Especially, against the resistant variants A17 and EFVR, bichromonol is more effective than the commercial drug nevirapine and might thus have potential to serve as a new anti-HIV lead.
Publikation

Ntie-Kang, F.; Telukunta, K. K.; Fobofou, S. A. T.; Chukwudi Osamor, V.; Egieyeh, S. A.; Valli, M.; Djoumbou-Feunang, Y.; Sorokina, M.; Stork, C.; Mathai, N.; Zierep, P.; Chávez-Hernández, A. L.; Duran-Frigola, M.; Babiaka, S. B.; Tematio Fouedjou, R.; Eni, D. B.; Akame, S.; Arreyetta-Bawak, A. B.; Ebob, O. T.; Metuge, J. A.; Bekono, B. D.; Isa, M. A.; Onuku, R.; Shadrack, D. M.; Musyoka, T. M.; Patil, V. M.; van der Hooft, J. J. J.; da Silva Bolzani, V.; Medina-Franco, J. L.; Kirchmair, J.; Weber, T.; Tastan Bishop, ?.; Medema, M. H.; Wessjohann, L. A.; Ludwig-Müller, J.; Computational Applications in Secondary Metabolite Discovery (CAiSMD): an online workshop J. Cheminform. 13, 64, (2021) DOI: 10.1186/s13321-021-00546-8

AbstractWe report the major conclusions of the online open-access workshop “Computational Applications in Secondary Metabolite Discovery (CAiSMD)” that took place from 08 to 10 March 2021. Invited speakers from academia and industry and about 200 registered participants from five continents (Africa, Asia, Europe, South America, and North America) took part in the workshop. The workshop highlighted the potential applications of computational methodologies in the search for secondary metabolites (SMs) or natural products (NPs) as potential drugs and drug leads. During 3 days, the participants of this online workshop received an overview of modern computer-based approaches for exploring NP discovery in the “omics” age. The invited experts gave keynote lectures, trained participants in hands-on sessions, and held round table discussions. This was followed by oral presentations with much interaction between the speakers and the audience. Selected applicants (early-career scientists) were offered the opportunity to give oral presentations (15 min) and present posters in the form of flash presentations (5 min) upon submission of an abstract. The final program available on the workshop website (https://caismd.indiayouth.info/) comprised of 4 keynote lectures (KLs), 12 oral presentations (OPs), 2 round table discussions (RTDs), and 5 hands-on sessions (HSs). This meeting report also references internet resources for computational biology in the area of secondary metabolites that are of use outside of the workshop areas and will constitute a long-term valuable source for the community. The workshop concluded with an online survey form to be completed by speakers and participants for the goal of improving any subsequent editions.
Publikation

Noviana, Z.; Vieira, S.; Pascual, J.; Fobofou, S. A. T.; Rohde, M.; Spröer, C.; Bunk, B.; Overmann, J.; Hypericibacter terrae gen. nov., sp. nov. and Hypericibacter adhaerens sp. nov., two new members of the family Rhodospirillaceae isolated from the rhizosphere of Hypericum perforatum Int. J. Syst. Evol. Microbiol. 70, 1850-1860, (2020) DOI: 10.1099/ijsem.0.003983

Two strains of the family Rhodospirillaceae were isolated from the rhizosphere of the medicinal plant Hypericum perforatum. Cells of both strains were Gram-stain-negative, motile by means of a single polar flagellum, non-spore-forming, non-capsulated, short rods that divided by binary fission. Colonies were small and white. Strains R5913T and R5959T were oxidase-positive, mesophilic, neutrophilic and grew optimally without NaCl. Both grew under aerobic and microaerophilic conditions and on a limited range of substrates with best results on yeast extract. Major fatty acids were C19 : 0 cyclo ω8c and C16 : 0; in addition, C18 : 1ω7c was also found as a predominant fatty acid in strain R5913T. The major respiratory quinone was ubiquinone 10 (Q-10). The DNA G+C contents of strains R5913T and R5959T were 66.0 and 67.4 mol%, respectively. 16S rRNA gene sequence comparison revealed that the closest relatives (<92 % similarity) of the strains are Oceanibaculum pacificum MCCC 1A02656T, Dongia mobilis CGMCC 1.7660T, Dongia soli D78T and Dongia rigui 04SU4-PT. The two novel strains shared 98.6 % sequence similarity and represent different species on the basis of low average nucleotide identity of their genomes (83.8 %). Based on the combined phenotypic, genomic and phylogenetic investigations, the two strains represent two novel species of a new genus in the family Rhodospirillaceae , for which the name Hypericibacter gen. nov. is proposed, comprising the type species Hypericibacter terrae sp. nov. (type strain R5913T=DSM 109816T=CECT 9472T) and Hypericibacter adhaerens sp. nov. (type strain R5959T=DSM 109817T=CECT 9620T).
Publikation

Jouda, J.-B.; Njoya, E. M.; Fobofou, S. A. T.; Zhou, Z. Y.; Qiang, Z.; Mbazoa, C. D.; Brandt, W.; Zhang, G.-l.; Wandji, J.; Wang, F.; Natural Polyketides Isolated from the Endophytic Fungus Phomopsis sp. CAM212 with a Semisynthetic Derivative Downregulating the ERK/IκBα Signaling Pathways Planta Med. 86, 1032-1042, (2020) DOI: 10.1055/a-1212-2930

AbstractThree previously undescribed natural products, phomopsinin A – C (1 – 3), together with three known compounds, namely, cis-hydroxymellein (4), phomoxanthone A (5) and cytochalasin L-696,474 (6), were isolated from the solid culture of Phomopsis sp. CAM212, an endophytic fungus obtained from Garcinia xanthochymus. Their structures were determined on the basis of spectroscopic data, including IR, NMR, and MS. The absolute configurations of 1 and 2 were assigned by comparing their experimental and calculated ECD spectra. Acetylation of compound 1 yielded 1a, a new natural product derivative that was tested together with other isolated compounds on lipopolysaccharide-stimulated RAW 264.7 cells. Cytochalasin L-696,474 (6) was found to significantly inhibit nitric oxide production, but was highly cytotoxic to the treated cells, whereas compound 1 slightly inhibited nitric oxide production, which was not significantly different compared to lipopolysaccharide-treated cells. Remarkably, the acetylated derivative of 1, compound 1a, significantly inhibited nitric oxide production with an IC50 value of 14.8 µM and no cytotoxic effect on treated cells, thereby showing the importance of the acetyl group in the anti-inflammatory activity of 1a. The study of the mechanism of action revealed that 1a decreases the expression of inducible nitric oxide synthase, cyclooxygenase 2, and proinflammatory cytokine IL-6 without an effect on IL-1β expression. Moreover, it was found that 1a exerts its anti-inflammatory activity in lipopolysaccharide-stimulated RAW 264.7 macrophage cells by downregulating the activation of ERK1/2 and by preventing the translocation of nuclear factor κB. Thus, derivatives of phomopsinin A (1), such as compound 1a, could provide new anti-inflammatory leads.
Publikation

Nganou, B. K.; Mbaveng, A. T.; Fobofou, S. A. T.; Fankam, A. G.; Bitchagno, G. T. M.; Simo Mpetga, J. D.; Wessjohann, L. A.; Kuete, V.; Efferth, T.; Tane, P.; Furoquinolines and dihydrooxazole alkaloids with cytotoxic activity from the stem bark of Araliopsis soyauxii Fitoterapia 133, 193-199, (2019) DOI: 10.1016/j.fitote.2019.01.003

Two new furoquinoline alkaloids, maculine B (1) and kokusaginine B (2) and one new dihydrooxazole alkaloid, veprisazole (3), along with four known compounds namely, N13-methyl-3-methoxyrutaecarpine (4), flindersiamine (5), skimmianine (6) and tilianin (7) were isolated from the methanol extract of the stem bark of Araliopsis soyauxii Engl. by various chromatographic methods. Their structures were determined using spectrometry and spectroscopic techniques including NMR and MS. The cytotoxicity of the new compounds compared to that of doxorubicin, the reference anticancer compound, was determined on a panel of nine cancer cell lines including sensitive and drug resistant phenotypes. The three previously undescribed alkaloids displayed selective activities. Maculine B (1), the most active one among the newly described compounds, exhibited IC50 below 30 μM against CCRF-CEM leukemia and U87MG glioblastoma cells.
Publikation

Fobofou, S. A. T.; Ares, K.; Arnold, N.; Imming, P.; New source report: Chemical constituents of Hypericum quartinianum (Hypericaceae), a sub-Saharan African plant species Biochem. Syst. Ecol. 85, 46-49, (2019) DOI: 10.1016/j.bse.2019.05.006

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Publikation

Feilcke, R.; Arnouk, G.; Raphane, B.; Richard, K.; Tietjen, I.; Andrae-Marobela, K.; Erdmann, F.; Schipper, S.; Becker, K.; Arnold, N.; Frolov, A.; Reiling, N.; Imming, P.; Fobofou, S. A. T.; Biological activity and stability analyses of knipholone anthrone, a phenyl anthraquinone derivative isolated from Kniphofia foliosa Hochst. J. Pharm. Biomed. Anal. 174, 277-285, (2019) DOI: 10.1016/j.jpba.2019.05.065

Knipholone (1) and knipholone anthrone (2), isolated from the Ethiopian medicinal plant Kniphofia foliosa Hochst. are two phenyl anthraquinone derivatives, a compound class known for biological activity. In the present study, we describe the activity of both 1 and 2 in several biological assays including cytotoxicity against four human cell lines (Jurkat, HEK293, SH-SY5Y and HT-29), antiplasmodial activity against Plasmodium falciparum 3D7 strain, anthelmintic activity against the model organism Caenorhabditis elegans, antibacterial activity against Aliivibrio fischeri and Mycobacterium tuberculosis and anti-HIV-1 activity in peripheral blood mononuclear cells (PBMCs) infected with HIV-1c. In parallel, we investigated the stability of knipholone (2) in solution and in culture media. Compound 1 displays strong cytotoxicity against Jurkat, HEK293 and SH-SY5Y cells with growth inhibition ranging from approximately 62–95% when added to cells at 50 μM, whereas KA (2) exhibits weak to strong activity with 26, 48 and 70% inhibition of cell growth, respectively. Both 1 and 2 possess significant antiplasmodial activity against Plasmodium falciparum 3D7 strain with IC50 values of 1.9 and 0.7 μM, respectively. These results complement previously reported data on the cytotoxicity and antiplasmodial activity of 1 and 2. Furthermore, compound 2 showed HIV-1c replication inhibition (growth inhibition higher than 60% at tested concentrations 0.5, 5, 15 and 50 μg/ml and an EC50 value of 4.3 μM) associated with cytotoxicity against uninfected PBMCs. The stability study based on preincubation, HPLC and APCI-MS (atmospheric-pressure chemical ionization mass spectrometry) analysis indicates that compound 2 is unstable in culture media and readily oxidizes to form compound 1. Therefore, the biological activity attributed to 2 might be influenced by its degradation products in media including 1 and other possible dimers. Hence, bioactivity results previously reported from this compound should be taken with caution and checked if they differ from those of its degradation products. To the best of our knowledge, this is the first report on the anti-HIV activity and stability analysis of compound 2.
Publikation

Kuete, V.; Dongmo Mafodong, F. L.; Celik, I.; Fobofou, S. A. T.; Ndontsa, B. L.; Karaosmanoğlu, O.; Wessjohann, L. A.; Tane, P.; Koparal, A. T.; Sivas, H.; In vitro cytotoxicity of compounds isolated from Desbordesia glaucescens against human carcinoma cell lines S. Afr. J. Bot. 111, 37-43, (2017) DOI: 10.1016/j.sajb.2017.03.031

Malignancies constitute a global health concern and chemotherapy remains the main mode of treatment. The present study was designed to evaluate the cytotoxicity of 8 compounds from Desbordesia glaucescens namely lanosta-7,24-dien-3-one (1), friedelanone (2), friedelanol (3), 3,3′-di-O-methylellagic acid (4), 3,3′,4′-tri-O-methylellagic acid (5), ellagic acid (6), 3′,4′-di-O-methylellagic acid 4-O-β-d-glucopyranoside (7) and 3,3′-di-O-methylellagic acid 4′-O-β-d-xylopyranoside (8) against 4 human carcinoma cell lines and normal CRL2120 fibroblasts. The neutral red uptake (NRU) assay was used for cytotoxicity testing. Caspase-Glo assay, cell cycle analysis, measurements of mitochondrial membrane potential (MMP) and levels of reactive oxygen species (ROS) were used to evaluate apoptosis induction. Compounds 4 and 6 as well as doxorubicin had IC50 values below 45 μM in the four tested cancer cell lines meanwhile other compounds displayed selective activity. The IC50 values ranged from 11.23 μM (towards breast adenocarcinoma MCF-7 cells) to 44.65μM (colon carcinoma Caco-2 cells) for 4, from 14.07 μM (towards MCF-7 cells) to 77.73 μM (Caco-2 cells) for 6 and from 0.07 μM (towards SPC212 cells) to 1.01 μM (A549 cells) for doxorubicin. Compound 4 induced apoptosis in MCF-7 cells mediated by MMP loss. The constituents of Desbordesia glaucescens and especially ellagic acid (6) and its derivative 4 are potential cytotoxic compounds that deserve more investigations towards developing novel antiproliferative drugs against human carcinoma.
Publikation

Koagne, R. R.; Bitchagno, G. T. M.; Fobofou, S. A. T.; Konga, I. S.; Tamokou, J. d. D.; Wessjohann, L. A.; Tane, P.; Rothtalazepane, A New Azepane from the Wood of Rothmannia talbotii (Rubiaceae) Nat. Prod. Commun. 12, 1435-1436, (2017) DOI: 10.1177/1934578X1701200912

Rothmannia talbotii, a hitherto chemically unexplored medicinal plant, is used in the Western Region of Cameroon to relieve fever. In our ongoing search for bioactive compounds from Cameroonian medicinal plants, a previously undescribed compound rothtalazepane (1), along with six known compounds, aitchisonide B (2), D-mannitol (3), β-D-glucopyranosyl-(6→1’)-β-D-glucopyranoside (4), monopalmitin (5), stigmasterol (6), and sitosterol 3-O-β-D-glucopyranoside (7) were isolated and characterized from the crude ethanol extract of the wood of R. talbotii. Rothtalazepane (1) exhibits no significant activity against several microbial strains, thus its function likely lies not in antimicrobial defense and it is not the active principle against urinary infections described for Rothmannia.
Publikation

Fobofou, S. A. T.; Franke, K.; Porzel, A.; Brandt, W.; Wessjohann, L. A.; Tricyclic Acylphloroglucinols from Hypericum lanceolatum and Regioselective Synthesis of Selancins A and B J. Nat. Prod. 79, 743-753, (2016) DOI: 10.1021/acs.jnatprod.5b00673

The chemical investigation of the chloroform extract of Hypericum lanceolatum guided by 1H NMR, ESIMS, and TLC profiles led to the isolation of 11 new tricyclic acylphloroglucinol derivatives, named selancins A–I (1–9) and hyperselancins A and B (10 and 11), along with the known compound 3-O-geranylemodin (12), which is described for a Hypericum species for the first time. Compounds 8 and 9 are the first examples of natural products with a 6-acyl-2,2-dimethylchroman-4-one core fused with a dimethylpyran unit. The new compounds 1–9 are rare acylphloroglucinol derivatives with two fused dimethylpyran units. Compounds 10 and 11 are derivatives of polycyclic polyprenylated acylphloroglucinols related to hyperforin, the active component of St. John’s wort. Their structures were elucidated by UV, IR, extensive 1D and 2D NMR experiments, HRESIMS, and comparison with the literature data. The absolute configurations of 5, 8, 10, and 11 were determined by comparing experimental and calculated electronic circular dichroism spectra. Compounds 1 and 2 were synthesized regioselectively in two steps. The cytotoxicity of the crude extract (88% growth inhibition at 50 μg/mL) and of compounds 1–6, 8, 9, and 12 (no significant growth inhibition up to a concentration of 10 mM) against colon (HT-29) and prostate (PC-3) cancer cell lines was determined. No anthelmintic activity was observed for the crude extract.
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