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Publikation

Ravindran, B. M.; Rizzo, P.; Franke, K.; Fuchs, J.; D’Auria, J.; Correction to: Simple and robust multiple shoot regeneration and root induction cycle from different explants of Hypericum perforatum L. genotypes Plant Cell Tiss. Organ Cult. 152, 19, (2023) DOI: 10.1007/s11240-022-02418-x

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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

Corrêa dos Santos, C. H.; Stark, P.; Rizzo, P.; Franke, K.; Wessjohann, L.; Prenylated acylphloroglucinol alcohols and peroxides from Hypericum coris Phytochem. Lett. 57, 11-15, (2023) DOI: 10.1016/j.phytol.2023.07.011

Two so far undescribed prenylated acylphloroglucinol derivatives were isolated from Hypericum coris (hypercorisins A-B) together with their two, also yet undescribed, peroxide derivatives (hypercorisins C-D), and seven known compounds (2-geranyloxy-1-(2-methylpropanoyl)-phloroglucinol, sucrose, vanillic acid 4-O-β-D-glucoside, chlorogenic acid, neochlorogenic acid, shikimic acid, quercitrin). The structures were determined by means of 1D and 2D NMR experiments and high-resolution mass spectrometry. Hypercorisins A, B and D induced complete inhibition of the gram-positive bacterium Bacillus subtilis at the highest concentration tested (100 μM) but showed no appreciable antibacterial effect on the gram-negative Aliivibrio fischeri nor cytotoxic activity on PC-3 or HCT-116 cancer cell lines.
Publikation

Chalo, D. M.; Franke, K.; Nchiozem-Ngnitedem, V.-A.; Kakudidi, E.; Origa-Oryem, H.; Namukobe, J.; Kloss, F.; Yenesew, A.; Wessjohann, L. A.; Prenylated isoflavanones with antimicrobial potential from the root bark of Dalbergia melanoxylon Metabolites 13, 678, (2023) DOI: 10.3390/metabo13060678

Dalbergia melanoxylon Guill. & Perr (Fabaceae) is widely utilized in the traditional medicine of East Africa, showing effects against a variety of ailments including microbial infections. Phytochemical investigation of the root bark led to the isolation of six previously undescribed prenylated isoflavanones together with eight known secondary metabolites comprising isoflavanoids, neoflavones and an alkyl hydroxylcinnamate. Structures were elucidated based on HR-ESI-MS, 1- and 2-D NMR and ECD spectra. The crude extract and the isolated compounds of D. melanoxylon were tested for their antibacterial, antifungal, anthelmintic and cytotoxic properties, applying established model organisms non-pathogenic to humans. The crude extract exhibited significant antibacterial activity against Gram-positive Bacillus subtilis (97% inhibition at 50 μg/mL) and antifungal activity against the phytopathogens Phytophthora infestans, Botrytis cinerea and Septoria tritici (96, 89 and 73% at 125 μg/mL, respectively). Among the pure compounds tested, kenusanone H and (3R)-tomentosanol B exhibited, in a panel of partially human pathogenic bacteria and fungi, promising antibacterial activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium showing MIC values between 0.8 and 6.2 μg/mL. The observed biological effects support the traditional use of D. melanoxylon and warrant detailed investigations of its prenylated isoflavanones as antibacterial lead compounds.
Publikation

Bin Ware, I.; Franke, K.; Dube, M.; Ali El Enshasy, H.; Wessjohann, L. A.; Characterization and bioactive potential of secondary metabolites isolated from Piper sarmentosum Roxb. Int. J. Mol. Sci. 24, 1328, (2023) DOI: 10.3390/ijms24021328

Piper sarmentosum Roxb. (Piperaceae) is a traditional medicinal plant in South-East Asian countries. The chemical investigation of leaves from this species resulted in the isolation of three previously not described compounds, namely 4″-(3-hydroxy-3-methylglutaroyl)-2″-β-D-glucopyranosyl vitexin (1), kadukoside (2), and 6-O-trans-p-coumaroyl-D-glucono-1,4-lactone (3), together with 31 known compounds. Of these known compounds, 21 compounds were isolated for the first time from P. sarmentosum. The structures were established by 1D and 2D NMR techniques and HR-ESI-MS analyses. The compounds were evaluated for their anthelmintic (Caenorhabditis elegans), antifungal (Botrytis cinerea, Septoria tritici and Phytophthora infestans), antibacterial (Aliivibrio fischeri) and cytotoxic (PC-3 and HT-29 human cancer cells lines) activities. Methyl-3-(4-methoxyphenyl)propionate (8), isoasarone (12), and trans-asarone (15) demonstrated anthelmintic activity with IC50 values between 0.9 and 2.04 mM. Kadukoside (2) was most active against S. tritici with IC50 at 5.0 µM and also induced 94% inhibition of P. infestans growth at 125 µM. Trans-asarone (15), piperolactam A (23), and dehydroformouregine (24) displayed a dose-dependent effect against B. cinerea from 1.5 to 125 µM up to more than 80% inhibition. Paprazine (19), cepharadione A (21) and piperolactam A (23) inhibited bacterial growth by more than 85% at 100 µM. Only mild cytotoxic effects were observed.
Publikation

Kappen, J.; Manurung, J.; Fuchs, T.; Vemulapalli, S. P. B.; Schmitz, L. M.; Frolov, A.; Agusta, A.; Muellner-Riehl, A. N.; Griesinger, C.; Franke, K.; Wessjohann, L. A.; Challenging structure elucidation of lumnitzeralactone, an ellagic acid derivative from the Mangrove Lumnitzera racemosa Mar. Drugs 21, 242, (2023) DOI: 10.3390/md21040242

The previously undescribed natural product lumnitzeralactone (1), which represents a derivative of ellagic acid, was isolated from the anti-bacterial extract of the Indonesian mangrove species Lumnitzera racemosa Willd. The structure of lumnitzeralactone (1), a proton-deficient and highly challenging condensed aromatic ring system, was unambiguously elucidated by extensive spectroscopic analyses involving high-resolution mass spectrometry (HRMS), 1D 1H and 13C nuclear magnetic resonance spectroscopy (NMR), and 2D NMR (including 1,1-ADEQUATE and 1,n-ADEQUATE). Determination of the structure was supported by computer-assisted structure elucidation (CASE system applying ACD-SE), density functional theory (DFT) calculations, and a two-step chemical synthesis. Possible biosynthetic pathways involving mangrove-associated fungi have been suggested.
Publikation

Bin Ware, I.; Franke, K.; Hussain, H.; Morgan, I.; Rennert, R.; Wessjohann, L. A.; Bioactive phenolic compounds from Peperomia obtusifolia Molecules 27, 4363, (2022) DOI: 10.3390/molecules27144363

Peperomia obtusifolia (L.) A. Dietr., native to Middle America, is an ornamental plant also traditionally used for its mild antimicrobial properties. Chemical investigation on the leaves of P. obtusifolia resulted in the isolation of two previously undescribed compounds, named peperomic ester (1) and peperoside (2), together with five known compounds, viz. N-[2-(3,4-dihydroxyphenyl)ethyl]-3,4-dihydroxybenzamide (3), becatamide (4), peperobtusin A (5), peperomin B (6), and arabinothalictoside (7). The structures of these compounds were elucidated by 1D and 2D NMR techniques and HREIMS analyses. Compounds 1–7 were evaluated for their anthelmintic (against Caenorhabditis elegans), antifungal (against Botrytis cinerea, Septoria tritici and Phytophthora infestans), antibacterial (against Bacillus subtilis and Aliivibrio fischeri), and antiproliferative (against PC-3 and HT-29 human cancer cell lines) activities. The known peperobtusin A (5) was the most active compound against the PC-3 cancer cell line with IC50 values of 25.6 µM and 36.0 µM in MTT and CV assays, respectively. This compound also induced 90% inhibition of bacterial growth of the Gram-positive B. subtilis at a concentration of 100 µM. In addition, compound 3 showed anti-oomycotic activity against P. infestans with an inhibition value of 56% by using a concentration of 125 µM. However, no anthelmintic activity was observed.
Publikation

Manurung, J.; Kappen, J.; Schnitzler, J.; Frolov, A.; Wessjohann, L. A.; Agusta, A.; Muellner-Riehl, A. N.; Franke, K.; Analysis of Unusual Sulfated Constituents and Anti-infective Properties of Two Indonesian Mangroves, Lumnitzera littorea and Lumnitzera racemosa (Combretaceae) Separations 8, 82, (2021) DOI: 10.3390/separations8060082

Lumnitzera littorea and Lumnitzera racemosa are mangrove species distributed widely along the Indonesian coasts. Besides their ecological importance, both are of interest owing to their wealth of natural products, some of which constitute potential sources for medicinal applications. We aimed to discover and characterize new anti-infective compounds, based on population-level sampling of both species from across the Indonesian Archipelago. Root metabolites were investigated by TLC, hyphenated LC-MS/MS and isolation, the internal transcribed spacer (ITS) region of rDNA was used for genetic characterization. Phytochemical characterization of both species revealed an unusual diversity in sulfated constituents with 3,3’,4’-tri-O-methyl-ellagic acid 4-sulfate representing the major compound in most samples. None of these compounds was previously reported for mangroves. Chemophenetic comparison of L. racemosa populations from different localities provided evolutionary information, as supported by molecular phylogenetic evidence. Samples of both species from particular locations exhibited anti-bacterial potential (Southern Nias Island and East Java against Gram-negative bacteria, Halmahera and Ternate Island against Gram-positive bacteria). In conclusion, Lumnitzera roots from natural mangrove stands represent a promising source for sulfated ellagic acid derivatives and further sulfur containing plant metabolites with potential human health benefits.
Publikation

Stark, P.; Zab, C.; Porzel, A.; Franke, K.; Rizzo, P.; Wessjohann, L. A.; PSYCHE—A Valuable Experiment in Plant NMR-Metabolomics Molecules 25, 5125, (2020) DOI: 10.3390/molecules25215125

1H-NMR is a very reproducible spectroscopic method and, therefore, a powerful tool for the metabolomic analysis of biological samples. However, due to the high complexity of natural samples, such as plant extracts, the evaluation of spectra is difficult because of signal overlap. The new NMR “Pure Shift” methods improve spectral resolution by suppressing homonuclear coupling and turning multiplets into singlets. The PSYCHE (Pure Shift yielded by Chirp excitation) and the Zangger–Sterk pulse sequence were tested. The parameters of the more suitable PSYCHE experiment were optimized, and the extracts of 21 Hypericum species were measured. Different evaluation criteria were used to compare the suitability of the PSYCHE experiment with conventional 1H-NMR. The relationship between the integral of a signal and the related bin value established by linear regression demonstrates an equal representation of the integrals in binned PSYCHE spectra compared to conventional 1H-NMR. Using multivariate data analysis based on both techniques reveals comparable results. The obtained data demonstrate that Pure Shift spectra can support the evaluation of conventional 1H-NMR experiments.
Publikation

Khine, M. M.; Arnold, N.; Franke, K.; Wessjohann, L. A.; Cardenolide glycosides from Streptocaulon tomentosum WIGHT & ARNOTT(Asclepiadaceae) in MYANMAR J. Myanmar Acad. Arts Sci. XVIII No. 1A, 1-11, (2020)

This  paper describes  the isolation and comparative studies on NMR spectra of cardenolide glycosides from Streptocaulon tomentosum Wight & Arnott (Asclepiadaceae).  Nine cardenolides were isolated from the roots of Streptocaulon tomentosum. by column chromatography and identified by NMR spectroscopy. They are 17α-H-periplogenin, 17α-H-periplogenin-β-D digitoxose,17α-H-periplogenin-β-D cymarose, 17α-H-periplogenin-β-glucosyl-(1-4)-2-O-acetyl-digitalose, 17β-H-periplogenin, 17β-H-periplogenin-β-D digitoxose, 17β-H-periplogenin-β-D cymarose, 17α -H-digitoxigenin, and 17 α-H-digitoxigenin-β-D-digitoxoside. Comparative studies on NMR spectra of cardenolide glycosides were carried out. Six cardenolides isolated from Streptocaulon tomentosum were tested for their antiproliferative activity in vitro against MCF-7 (human breast cancer cell line) and L 929 (mouse fibroblast cell line). Among these six cardenolides, 17α-H-periplogenin-3-O-β-D-digitoxoside and 17α-H-periplogenin-3-O-β-D-cymaroside exhibit significant antiproliferative activity (IC50 values, < 1μM) against MCF-7. Four cardenolides  were examined for their cellular viability in the tumor cell and  U 937  (human leukemic cell line) at concentrations 100 μM, 10 μM, and 1 μM. All these four cardenolides  show the induction of apoptosis at 100 μM and 10 μM in both cell lines.

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