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Publications - Bioorganic Chemistry

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Publications

Farag, M. A.; Porzel, A.; Wessjohann, L. A.; Unraveling the active hypoglycemic agent trigonelline in Balanites aegyptiaca date fruit using metabolite fingerprinting by NMR J. Pharm. Biomed. Anal. 115, 383-387, (2015) DOI: 10.1016/j.jpba.2015.08.003

Trigonelline (3-carboxy-1-methyl pyridinium) was identified as a relevant bioactivity and taste imparting component in Balanites aegyptiaca fruit, using 1H NMR of crude extracts without any fractionation or isolation step. The structural integrity of trigonelline was established within the extract matrix via1H NMR, 1H–1H COSY, HMQC and HMBC and by comparison with authentic standard. A quantitative 1H NMR method (qHNMR) was used to determine trigonelline concentrations in the peel and pulp of B. aegyptiaca fruit of 8 and 13 mg g−1, respectively. Trigonelline so far has not been reported from B. aegyptiaca or its genus as it easily escapes LC–MS based detection. Its discovery provides novel insight into the balanite fruits antidiabetic properties as the compound is known for a pronounced hypoglycemic effect. In addition, it is likely to impart the perceptible bitter taste portion to balanites sweet bitter taste. UPLC–MS of the crude extract additionally revealed the fruit flavonoid pattern showing quercetin/isorhamnetin flavonol conjugates in addition to epicatechin, the latter being present at much lower levels.
Publications

Farag, M. A.; Porzel, A.; Wessjohann, L. A.; Unequivocal glycyrrhizin isomer determination and comparative in vitro bioactivities of root extracts in four Glycyrrhiza species J. Adv. Res. 6, 99-104, (2015) DOI: 10.1016/j.jare.2014.05.001

Glycyrrhiza glabra, commonly known as licorice, is a popular herbal supplement used for the treatment of chronic inflammatory conditions and as sweetener in the food industry. This species contains a myriad of phytochemicals including the major saponin glycoside glycyrrhizin (G) of Glycyrrhetinic acid (GA) aglycone. In this study, 2D-ROESY NMR technique was successfully applied for distinguishing 18α and 18β glycyrrhetinic acid (GA). ROESY spectra acquired from G. glabra, Glycyrrhiza uralensis and Glycyrrhiza inflata crude extracts revealed the presence of G in its β-form. Anti-inflammatory activity of four Glycyrrhiza species, G, glabra, G. uralensis, G. inflata, and G. echinata roots was assessed against COX-1 inhibition revealing that phenolics rather than glycyrrhizin are biologically active in this assay. G. inflata exhibits a strong cytotoxic effect against PC3 and HT29 cells lines, whereas other species are inactive. This study presents an effective NMR method for G isomer assignment in licorice extracts that does not require any preliminary chromatography or any other purification step.
Publications

Farag, M. A.; Al-Mahdy, D. A.; Salah El Dine, R.; Fahmy, S.; Yassin, A.; Porzel, A.; Brandt, W.; Structure-Activity Relationships of Antimicrobial Gallic Acid Derivatives from Pomegranate and Acacia Fruit Extracts against Potato Bacterial Wilt Pathogen Chem. Biodivers. 12, 955-962, (2015) DOI: 10.1002/cbdv.201400194

Bacterial wilts of potato, tomato, pepper, and or eggplant caused by Ralstonia solanacearum are among the most serious plant diseases worldwide. In this study, the issue of developing bactericidal agents from natural sources against R. solanacearum derived from plant extracts was addressed. Extracts prepared from 25 plant species with antiseptic relevance in Egyptian folk medicine were screened for their antimicrobial properties against the potato pathogen R. solancearum by using the disc‐zone inhibition assay and microtitre plate dilution method. Plants exhibiting notable antimicrobial activities against the tested pathogen include extracts from Acacia arabica and Punica granatum. Bioactivity‐guided fractionation of A. arabica and P. granatum resulted in the isolation of bioactive compounds 3,5‐dihydroxy‐4‐methoxybenzoic acid and gallic acid, in addition to epicatechin. All isolates displayed significant antimicrobial activities against R. solanacearum (MIC values 0.5–9 mg/ml), with 3,5‐dihydroxy‐4‐methoxybenzoic acid being the most effective one with a MIC value of 0.47 mg/ml. We further performed a structure–activity relationship (SAR) study for the inhibition of R. solanacearum growth by ten natural, structurally related benzoic acids.
Publications

Farag, M. A.; Sakna, S. T.; El-fiky, N. M.; Shabana, M. M.; Wessjohann, L. A.; Phytochemical, antioxidant and antidiabetic evaluation of eight Bauhinia L. species from Egypt using UHPLC–PDA–qTOF-MS and chemometrics Phytochemistry 119, 41-50, (2015) DOI: 10.1016/j.phytochem.2015.09.004

Bauhinia L. (Fabaceae) comprises ca. 300–350 plant species, many of which are traditionally used in folk medicine for their antidiabetic, antioxidant and anti-inflammatory effects. Bauhinia s.l. recently has been subdivided into 9 genera based on phylogenetic data: Bauhinia s.str., Barklya, Brenierea, Gigasiphon, Lysiphyllum, Phanera, Piliostigma, Schnella (American Phanera) and Tylosema. The aerial parts of 8 species corresponding to 5 genera were analyzed: Bauhinia forficata, Bauhinia variegata, B. variegata var. candida, Bauhinia galpinii, Schnella glabra, Piliostigma racemosa, Phanera vahlii and Lysiphyllum hookeri. Leaves and shoots were subjected to metabolite profiling via UHPLC–PDA–qTOF-MS coupled to multivariate data analyzes to identify compound compositional differences. A total of 90 metabolites were identified including polyphenols and fatty acids; flavonoid conjugates accounted for most of the metabolite variation observed. This study provides a comprehensive map of polyphenol composition in Bauhinia and phytochemical species aggregations are consistent with recent Bauhinia genus taxonomic relationship derived from phylogenetic studies. DPPH radical scavenging and α-glucosidase inhibitory assays were also performed to assess selected aspects of the antioxidant and antidiabetic potential for the examined species with respect to metabolite profiles.
Publications

Farag, M. A.; Porzel, A.; Mahrous, E. A.; El-Massry, M. M.; Wessjohann, L. A.; Integrated comparative metabolite profiling via MS and NMR techniques for Senna drug quality control analysis Anal. Bioanal. Chem. 407, 1937-1949, (2015) DOI: 10.1007/s00216-014-8432-1

Senna alexandrina Mill (Cassia acutifolia and Cassia angustifolia) are used for the laxative medicine Senna. Leaves and pods from two geographically different sources were distinguished from each other via proton nuclear magnetic resonance (1H-NMR) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. Under optimized conditions, we were able to simultaneously quantify and identify 107 metabolites including 21 anthraquinones, 24 bianthrones (including sennosides), 5 acetophenones, 25 C/O-flavonoid conjugates, 5 xanthones, 3 naphthalenes, 2 further phenolics, and 9 fatty acids. Principal component analysis (PCA) and hierarchical clustering analysis (HCA) were used to define both similarities and differences among samples. For sample classification based on tissue type (leaf and pod), both UPLC-MS and NMR were found to be more effective in separation than on geographical origin. Results reveal that the amounts of the major classes of bioactives in Senna, i.e., flavonoids and sennosides, varied significantly among organs. Leaves contained more flavonoids and ω-3 fatty acids but fewer benzophenone derivatives than pods. In contrast, pods were more enriched in bianthrones (sennosides). PCA analysis was found to be equally effective in predicting the origin of the commercial Senna preparation using NMR and/or UPLC-MS datasets. Furthermore, a selection of six so far uninvestigated Senna species were analyzed by UPLC-MS. Results revealed that the Senna alata leaf in terms of secondary metabolite composition is the most closely related species to S. alexandrina Mill, showing the highest levels of the anthraquinone “rhein” and flavonoid conjugates. To the best of our knowledge, this study provides the first approach utilizing both UPLC-MS and NMR to reveal secondary metabolite compositional differences among Senna species.
Publications

Eichhorn, T.; Hey-Hawkins, E.; Maksimović-Ivanić, D.; Mojić, M.; Schmidt, J.; Mijatović, S.; Schmidt, H.; Kaluđerović, G. N.; Binuclear dichlorido(η6-p-cymene)ruthenium(II) complexes with bis(nicotinate)- and bis(isonicotinate)-polyethylene glycol ester ligands Appl. Organomet. Chem. 29, 20-25, (2015) DOI: 10.1002/aoc.3238

Neutral binuclear ruthenium complexes 1, 2, 3, 4, 5, 6, 7, 8 of the general formula [{RuCl2(η6‐p‐cym)}2 μ‐(N∩N)] (N∩N = bis(nicotinate)‐ and bis(isonicotinate)‐polyethylene glycol esters: (3‐py)COO(CH2CH2O)nCO(3‐py) and (4‐py)COO(CH2CH2O)nCO(4‐py), n =1–4), as well as mononuclear [RuCl2(η6‐p‐cym)((3‐py)COO(CH2CH2OCH3)‐κN)], complex 9, were synthesized and characterized using elemental analysis and electrospray ionization high‐resolution mass spectrometry, infrared, 1H NMR and 13C NMR spectroscopies. Stability of the binuclear complexes in the presence of dimethylsulfoxide was studied. Furthermore, formation of a cationic complex containing bridging pyridine‐based bidentate ligand was monitored using 1H NMR spectroscopy. Ligand precursors, polyethylene glycol esters of nicotinic (L1 · 2HCl–L4 · 2HCl and L9 · HCl) and isonicotinic acid dihydrochlorides (L5 · 2HCl–L8 · 2HCl), binuclear ruthenium(II) complexes 1, 2, 3, 4, 5, 6, 7, 8 and mononuclear complex 9 were tested for in vitro cytotoxicity against 518A2 (melanoma), 8505C (anaplastic thyroid cancer), A253 (head and neck tumour), MCF‐7 (breast tumour) and SW480 (colon carcinoma) cell lines.
Publications

Eichenberg, D.; Purschke, O.; Ristok, C.; Wessjohann, L.; Bruelheide, H.; Trade-offs between physical and chemical carbon-based leaf defence: of intraspecific variation and trait evolution J. Ecol. 103, 1667-1679, (2015) DOI: 10.1111/1365-2745.12475

Despite recent advances in studies on trade‐offs between plant defence traits, little is known about whether trade‐offs reflect (i) evolutionary constraints at the species level or (ii) allocation constraints at the individual level. Here, we asked to which degree physical and chemical carbon‐based leaf defence traits covary within and across species.We assessed leaf toughness, leaf total phenolic and tannin concentrations for 51 subtropical tree species. Species trait means, sample‐specific values and phylogenetically independent contrasts were used in regression analyses. Phylogenetic signals and trait evolution were assessed along the phylogeny.Analyses of species‐level trait means revealed significant negative trait covariations between physical and chemical defence traits in analyses over all species. These covariations were inconsistent at the within‐species level. All three defence aspects showed strong phylogenetic signals, but differed in the degree of conservatism along the phylogeny. Inclusion of intraspecific trait variability significantly decreased the strength of these covariations. Strong negative covariations were detected between physical and chemical defence traits when phylogenetic non‐independence was accounted for.Synthesis. We addressed two sources of variation (allocation and evolution) independently from each other in the context of trait interrelationships. The observed negative covariations hint at the existence of a trade‐off between physical and chemical defence traits. The finding that intraspecific trait variation contributed less to this relationship suggests that the trade‐off is dominated by evolutionary constraints rather than by carbon allocation constraints.
Publications

Echemendía, R.; de La Torre, A. F.; Monteiro, J. L.; Pila, M.; Corrêa, A. G.; Westermann, B.; Rivera, D. G.; Paixão, M. W.; Highly Stereoselective Synthesis of Natural-Product-Like Hybrids by an Organocatalytic/Multicomponent Reaction Sequence Angew. Chem. 127, 7731-7735, (2015) DOI: 10.1002/ange.201412074

In an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one‐pot process comprising an organocatalytic conjugate addition of 1,3‐dicarbonyls to α,β‐unsaturated aldehydes followed by an intramolecular isocyanide‐based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity‐generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties.
Publications

Echemendía, R.; de La Torre, A. F.; Monteiro, J. L.; Pila, M.; Corrêa, A. G.; Westermann, B.; Rivera, D. G.; Paixão, M. W.; Highly Stereoselective Synthesis of Natural-Product-Like Hybrids by an Organocatalytic/Multicomponent Reaction Sequence Angew. Chem. Int. Ed. 54, 7621-7625, (2015) DOI: 10.1002/anie.201412074

In an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one‐pot process comprising an organocatalytic conjugate addition of 1,3‐dicarbonyls to α,β‐unsaturated aldehydes followed by an intramolecular isocyanide‐based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity‐generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties.
Publications

Dippe, M.; Brandt, W.; Rost, H.; Porzel, A.; Schmidt, J.; Wessjohann, L. A.; Rationally engineered variants of S-adenosylmethionine (SAM) synthase: reduced product inhibition and synthesis of artificial cofactor homologues Chem. Commun. 51, 3637-3640, (2015) DOI: 10.1039/c4cc08478k

S-Adenosylmethionine (SAM) synthase was engineered for biocatalytic production of SAM and long-chain analogues by rational re-design. Substitution of two conserved isoleucine residues extended the substrate spectrum of the enzyme to artificial S-alkylhomocysteines. The variants proved to be beneficial in preparative synthesis of SAM (and analogues) due to a much reduced product inhibition.
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