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Publikation

Frey, M.; Bathe, U.; Meink, L.; Balcke, G. U.; Schmidt, J.; Frolov, A.; Soboleva, A.; Hassanin, A.; Davari, M. D.; Frank, O.; Schlagbauer, V.; Dawid, C.; Tissier, A.; Combinatorial biosynthesis in yeast leads to over 200 diterpenoids Metab. Eng. 82, 193-200, (2024) DOI: 10.1016/j.ymben.2024.02.006

Diterpenoids form a diverse group of natural products, many of which are or could become pharmaceuticals or industrial chemicals. The modular character of diterpene biosynthesis and the promiscuity of the enzymes involved make combinatorial biosynthesis a promising approach to generate libraries of diverse diterpenoids. Here, we report on the combinatorial assembly in yeast of ten diterpene synthases producing (+)-copalyldiphosphate-derived backbones and four cytochrome P450 oxygenases (CYPs) in diverse combinations. This resulted in the production of over 200 diterpenoids. Based on literature and chemical database searches, 162 of these compounds can be considered new-to-Nature. The CYPs accepted most substrates they were given but remained regioselective with few exceptions. Our results provide the basis for the systematic exploration of the diterpenoid chemical space in yeast using sequence databases.
Publikation

Laub, A.; Sendatzki, A.-K.; Palfner, G.; Wessjohann, L. A.; Schmidt, J.; Arnold, N.; HPTLC-DESI-HRMS-Based Profiling of Anthraquinones in Complex Mixtures—A Proof-of-Concept Study Using Crude Extracts of Chilean Mushrooms Foods 9, 156, (2020) DOI: 10.3390/foods9020156

High-performance thin-layer chromatography (HPTLC) coupled with negative ion desorption electrospray ionization high-resolution mass spectrometry (DESI-HRMS) was used for the analysis of anthraquinones in complex crude extracts of Chilean dermocyboid Cortinarii. For this proof-of-concept study, the known anthraquinones emodin, physcion, endocrocin, dermolutein, hypericin, and skyrin were identified by their elemental composition. HRMS also allowed the differentiation of the investigated anthraquinones from accompanying compounds with the same nominal mass in the crude extracts. An investigation of the characteristic fragmentation pattern of skyrin in comparison with a reference compound showed, exemplarily, the feasibility of the method for the determination of these coloring, bioactive and chemotaxonomically important marker compounds. Accordingly, we demonstrate that the coupling of HPTLC with DESI-HRMS represents an advanced and efficient technique for the detection of anthraquinones in complex matrices. This analytical approach may be applied in the field of anthraquinone-containing food and plants such as Rheum spp. (rhubarb), Aloe spp., Morinda spp., Cassia spp. and others. Furthermore, the described method can be suitable for the analysis of anthraquinone-based colorants and dyes, which are used in the food, cosmetic, and pharmaceutical industry.
Publikation

Schmidt, J.; Kuck, D.; Franke, K.; Sultani, H.; Laub, A.; Wessjohann, L. A.; The unusual fragmentation of long-chain feruloyl esters under negative ion electrospray conditions J. Mass Spectrom. 54, 549-556, (2019) DOI: 10.1002/jms.4357

Long‐chain ferulic acid esters, such as eicosyl ferulate (1), show a complex and analytically valuable fragmentation behavior under negative‐ion electrospay collision‐induced dissociation ((‐)‐ESI‐CID) mass spectrometry, as studied by use of a high‐resolution (Orbitrap) mass spectrometer. In a strong contrast to the very simple fragmentation of the [M + H]+ ion, which is discussed briefly, the deprotonated molecule, [M ‐ H]‐, exhibits a rich secondary fragmentation chemistry. It first loses a methyl radical (MS2) and the ortho‐quinoid [M ‐ H ‐ Me]‐• radical anion thus formed then dissociates by loss of an extended series of neutral radicals, CnH2n+1• (n = 0‐16) from the long alkyl chain, in competition with the expulsion of CO and CO2 (MS3). The further fragmentation (MS4) of the [M ‐ H ‐ Me ‐ C3H7]‐ ion, discussed as an example, and the highly specific losses of alkyl radicals from the [M ‐ H ‐ Me ‐ CO]‐• and [M ‐ H ‐ Me ‐ CO2]‐• ions provide some mechanistic and structural insights.
Publikation

Dippe, M.; Bauer, A.-K.; Porzel, A.; Funke, E.; Müller, A. O.; Schmidt, J.; Beier, M.; Wessjohann, L. A.; Coenzyme A‐Conjugated Cinnamic Acids – Enzymatic Synthesis of a CoA‐Ester Library and Application in Biocatalytic Cascades to Vanillin Derivatives Adv. Synth. Catal. 361, 5346-5350, (2019) DOI: 10.1002/adsc.201900892

We present a bioorthogonal method for the ligation of coenzyme A (CoA) with cinnamic acids. The reaction, which is the initial step in the biosynthesis of a multitude of bioactive secondary metabolites, is catalyzed by a promiscuous plant ligase and yields CoA conjugates with different functionalization in high purity and without formation of by‐products. Its applicability in biosynthetic cascades is shown for the direct transformation of cinnamic acids into natural benzaldehydes (like vanillin) or artificial derivatives (e. g. ethylvanillin).
Publikation

Melaku, Y.; Arnold, N.; Schmidt, J.; Dagne, E.; Analysis of the husk and kernel of the seeds of Moringa stenopetala Bull. Chem. Soc. Ethiop. 31, 107-113, (2017) DOI: 10.4314/bcse.v31i1.9

The ethanol extract of the kernel of the endemic plant Moringa stenopetala after silica gel column chromatography led to the isolation of 4-(α-L-rhamnopyranosyloxy)benzyl glucosinolate (1) and sucrose. The oil obtained by Soxhlet extraction with petrol was trans-esterified with BF3-MeOH and analyzed by GC-MS. The results showed the presence of diverse fatty acids namely palmitic (11%), palmitoleic (1.2%), stearic (11%), oleic (63%), linoleic (1.2%), arachidic (6%) and the rare behenic acids (6%). The white glossy seed husk which comprises 25% of the whole seed yielded two compounds namely 4-(σ-L-rhamnosyloxy)benzyl alcohol (2) and allantoin (3). To the best of our knowledge this is the first report of compound 2 as a natural product. Allantoin is reported here for the first time from the genus Moringa.
Publikation

Greff, A.; Porzel, A.; Schmidt, J.; Palfner, G.; Arnold, N.; Pigment pattern of the Chilean mushroom Dermocybe nahuelbutensis Garrido & E. Horak Rec. Nat. Prod. 11, 547-551, (2017) DOI: 10.25135/rnp.69.17.01.027

Fruiting bodies of the Chilean mushroom Dermocybe nahuelbutenis Garrido & E. Horak (syn.: Cortinariusnahuelbutensis (Garrido & E. Horak) E. Valenz. & G. Moreno) were chemically investigated for the first time andafforded the new dimeric anthraqinone 7,7'-emodinphyscion (1) beside the know anthraquinones dermolutein (2),endocrocin (3), skyrin (4) and the dimeric pre-anthraquinone derivative flavomannin C (5). The chemotaxonomicsignificance of the pigments is discussed.
Publikation

Melaku, Y.; Worku, T.; Tadesse, Y.; Mekonnen, Y.; Schmidt, J.; Arnold, N.; Dagne, E.; Antiplasmodial Compounds from Leaves of Dodonaea angustifolia Curr. Bioact. Comp. 13, 268-273, (2017) DOI: 10.2174/1573407213666170403121222

Background: Dodonaea angustifolia is used in Ethiopian traditional medicine to treat malaria. The objective of this work was to conduct bioassay guided fractionation of the leaves of D. angustifolia using Plasmodium berghei infected mice.Method: The antiplasmodial activity of the extracts and pure compounds was evaluated using the standard Peter’s four-day suppressive method. The structures of isolated compounds were elucidated using chemical and spectroscopic methods.Results: In this study, the ethyl acetate soluble portion of the 80% aqueous MeOH extract of the leaves significantly suppressed parasitaemia in Plasmodium berghei infected mice (80.28% at 150 mg/kg). Three active compounds which exhibited significant percent suppression of parasitaemia by 81% at 40 mg/kg, 80% at 50 mg/kg and 70% at 40 mg/kg, respectively were identified. These are the flavanone pinocembrin (1), the flavanol santin (2) and the clerodane diterpene 2-hydroxy-15,16-epoxyceloda-3,13(16),14-trien-18-oic acid (3). Under similar conditions, chloroquine suppressed parasitaemia by 100% at 25 mg/kg. Chemical study of the ethanol extract of the leaves yielded 5,7,4'-trihydroxy-3,6-dimethoxyflavone (4), ent-16-hydroxy-labdan-3,8-dihydroxy,13(14)-en-15,16-olide (5) and 5,6,7-trihydroxy-3,4'-dimethoxyflavone (6). Compound 6 has not been reported before as a natural product.Conclusion: From the leaves of D. angustifolia, three compounds with significant antiplasmodial activities were isolated and characterized, with pinocembrin as the most active compound.
Publikation

Quang, D. N.; Wagner, C.; Merzweiler, K.; Abate, D.; Porzel, A.; Schmidt, J.; Arnold, N.; Pyrofomins A-D, polyoxygenated sesquiterpenoids from Pyrofomes demidoffii Fitoterapia 112, 229-232, (2016) DOI: 10.1016/j.fitote.2016.06.004

Pyrofomins A-D, four polyoxygenated sesquiterpenoids have been isolated from the methanolic extract of the fruit bodies of Pyrofomes demidoffii. Their structures are elucidated by IR, HR-FTICR-MS, and 2D NMR spectroscopy. Furthermore, the cedrane carbon skeleton of pyrofomin A (1) is confirmed by X-ray crystallographic analysis. The sesquiterpenoids 1–4 show neither cytotoxicity against KB cells nor antimicrobial activity.
Publikation

Otto, A.; Laub, A.; Haid, M.; Porzel, A.; Schmidt, J.; Wessjohann, L.; Arnold, N.; Tulasporins A–D, 19-Residue Peptaibols from the Mycoparasitic Fungus Sepedonium tulasneanum Nat. Prod. Commun. 11, 1821-1824, (2016) DOI: 10.1177/1934578X1601101212

Four new 19-residue peptaibols, named tulasporins A–D (1–4), were isolated from the semi-solid cultures of Sepedonium tulasneanum. Their structures were elucidated on the basis of extensive ESI-HRMSn fragmentation studies as well as 1H NMR spectroscopic analyses. Interestingly, the structures of tulasporins A–D (1–4) resemble those of chrysospermins isolated earlier from cultures of S. chrysospermum. Previously, it was hypothesized that the peptaibol production by Sepedonium species correlates with the morphology of the aleurioconidia, as exclusively round-shaped aleurioconidia forming species produced peptaibols. Since the investigated Sepedonium tulasneanum produces oval aleurioconidia, this study can be considered as the first report of peptaibols from a Sepedonium strain with oval-shaped aleurioconidia. Thus, it could be demonstrated that both round as well as oval aleurioconidia forming Sepedonium species are able to produce peptaibols. Tulasporins A-D (1–4), when tested against phytopathogenic fungi, exhibited good growth inhibitory activity against both Botrytis cinerea and Phytophthora infestans, while they were devoid of significant activity against Septoria tritici.
Publikation

Otto, A.; Porzel, A.; Schmidt, J.; Brandt, W.; Wessjohann, L.; Arnold, N.; Structure and Absolute Configuration of Pseudohygrophorones A12 and B12, Alkyl Cyclohexenone Derivatives from Hygrophorus abieticola (Basidiomycetes) J. Nat. Prod. 79, 74-80, (2016) DOI: 10.1021/acs.jnatprod.5b00675

Pseudohygrophorones A(12) (1) and B(12) (2), the first naturally occurring alkyl cyclohexenones from a fungal source, and the recently reported hygrophorone B(12) (3) have been isolated from fruiting bodies of the basidiomycete Hygrophorus abieticola Krieglst. ex Gröger & Bresinsky. Their structures were assigned on the basis of extensive one- and two-dimensional NMR spectroscopic analysis as well as ESI-HRMS measurements. The absolute configuration of the three stereogenic centers in the diastereomeric compounds 1 and 2 was established with the aid of (3)JH,H and (4)JH,H coupling constants, NOE interactions, and conformational analysis in conjunction with quantum chemical CD calculations. It was concluded that pseudohygrophorone A(12) (1) is 4S,5S,6S configured, while pseudohygrophorone B(12) (2) was identified as the C-6 epimer of 1, corresponding to the absolute configuration 4S,5S,6R. In addition, the mass spectrometric fragmentation behavior of 1-3 obtained by the higher energy collisional dissociation method allows a clear distinction between the pseudohygrophorones (1 and 2) and hygrophorone B(12) (3). The isolated compounds 1-3 exhibited pronounced activity against phytopathogenic organisms.
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