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Publications

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.
Publications

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.
Publications

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).
Publications

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.
Publications

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.
Publications

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.
Publications

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.
Publications

Arnold, N.; Palfner, G.; Kuhnt, C.; Schmidt, J.; Chemistry of the earthy odour of basidiomata of Cortinarius hinnuleus (Basidiomycota, Agaricales) Österr. Z. Pilzk. 25, 5-10, (2016)

Cortinarius hinnuleus (Earthy Webcap), a common mycorrhizal mushroom in Central Europe, is characterized by a mouldy earthy odour. The relevant volatile compounds were detected by gas chromatography-mass spectrometry using headspace-solid phase microextraction technology and identified as geosmin, ß-caryophyllene and ß-barbatene together with the C8-volatiles 1-octen-3-ol, 1-octen-3-one, octan-3-ol, octan-3-one, and 2-octen-1-ol.
Publications

Schmidt, J.; Negative ion electrospray high-resolution tandem mass spectrometry of polyphenols J. Mass Spectrom. 51, 33-43, (2016) DOI: 10.1002/jms.3712

Representative compounds with a 1,3‐dihydroxybenzene substructure belonging to different important polyphenol classes (stilbenes, flavones, isoflavones, flavonols, flavanones, flavanols, phloroglucinols, anthraquinones and bisanthraquinones) were investigated based on detailed high‐resolution tandem mass spectrometry measurements with an Orbitrap system under negative ion electrospray conditions. The mass spectral behaviour of these compound classes was compared among each other not only with respect to previously described losses of CO, CH2CO and C3O2 but also concerning the loss of CO2 and successive specific fragmentations. Furthermore, some unusual fragmentations such as the loss of a methyl radical during mass spectral decomposition are discussed. The obtained results demonstrate both similarities and differences in their mass spectral fragmentation under MSn conditions, allowing a characterization of the corresponding compound type.
Publications

Al-Fatimi, M.; Ali, N. A. A.; Kilian, N.; Franke, K.; Arnold, N.; Kuhnt, C.; Schmidt, J.; Lindequist, U.; Ethnobotany, chemical constituents and biological activities of the flowers of Hydnora abyssinica A.Br. (Hydnoraceae) Pharmazie 71, 222-226, (2016) DOI: 10.1691/ph.2016.5808

Hydnora abyssinica A.Br. (Hydnoraceae), a holoparasitic herb, is for the first time recorded for Abyan governorate of South Yemen. Flowers of this species were studied for their ethnobotanical, biological and chemical properties for the first time. In South Yemen, they are traditionally used as wild food and to cure stomach diseases, gastric ulcer and cancer. Phytochemical analysis of the extracts showed the presence of terpenes, tannins, phenols, and flavonoids. The volatile components of the air-dried powdered flowers were identified using a static headspace GC/MS analysis as acetic acid, ethyl acetate, sabinene, α-terpinene, (+)-D-limonene and γ-terpinene. These volatile compounds that characterize the odor and taste of the flowers were detected for the first time in a species of the family Hydnoraceae. The flowers were extracted by n-hexane, dichlormethane, ethyl acetate, ethanol, methanol and water. With exception of the water extract all extracts demonstrated activities against Gram-positive bacteria as well as remarkable radical scavenging activities in DPPH assay. Ethyl acetate, methanol and water extracts exhibited good antifungal activities. The cytotoxic activity of the extracts against FL cells, measured in neutral red assay, was only weak (IC50 > 500 μg /mL). The results justify the traditional use of the flowers of Hydnora abyssinica in South Yemen.
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