Daniela Schuster | University of Innsbruck (original) (raw)

Papers by Daniela Schuster

Mediators of inflammation, 2014

Cyclooxygenases and lipoxygenases are proinflammatory enzymes; the former affects platelet aggreg... more Cyclooxygenases and lipoxygenases are proinflammatory enzymes; the former affects platelet aggregation, vasoconstriction, vasodilatation and later the development of atherosclerosis. Red wines from Georgia and central and western Europe inhibited cyclooxygenase-1 (COX-1) activity in the range of 63-94%, cyclooxygenase-2 (COX-2) activity in the range of 20-44% (tested at a concentration of 5 mL/L), and 5-lipoxygenase (5-LOX) activity in the range of 72-84% (at a concentration of 18.87 mL/L). White wines inhibited 5-LOX in the range of 41-68% at a concentration of 18.87 mL/L and did not inhibit COX-1 and COX-2. Piceatannol (IC 50 = 0.76 M) was identified as a strong inhibitor of 5-LOX followed by luteolin (IC 50 = 2.25 M), quercetin (IC 50 = 3.29 M), and myricetin (IC 50 = 4.02 M). trans-Resveratrol was identified as an inhibitor of COX-1 (IC 50 = 2.27 M) and COX-2 (IC 50 = 3.40 M). Red wine as a complex mixture is a powerful inhibitor of COX-1, COX-2, and 5-LOX, the enzymes involved in eicosanoid biosynthetic pathway.

European Journal of Medicinal Chemistry, 2015

Several new 4-phenylpyrimidine-2(1H)-thiones have been prepared and investigated for their potenc... more Several new 4-phenylpyrimidine-2(1H)-thiones have been prepared and investigated for their potencies to inhibit COX-1 and COX-2 enzymes, and COX-2 expression in THP-1 cells. Structure-activity-relationships and physicochemical parameters are discussed. Pharmacophore screening and docking studies were carried out for the most active compound.

The Journal of Steroid Biochemistry and Molecular Biology, 2013

The prevalence of sex hormone-dependent cancers, reproductive problems, obesity, and cardiovascul... more The prevalence of sex hormone-dependent cancers, reproductive problems, obesity, and cardiovascular complications has risen especially in the Western world. It has been suggested, that the exposure to various endocrine disrupting chemicals (EDCs) contributes to the development and progression of these diseases. EDCs can interfere with various proteins: nuclear steroid hormone receptors, such as estrogen-, androgen-, glucocorticoid- and mineralocorticoid receptors (ER, AR, GR, MR), and enzymes that are involved in steroid hormone synthesis and metabolism, for example hydroxysteroid dehydrogenases (HSDs). Numerous chemicals are known as endocrine disruptors. However, the mechanism of action for most of these EDCs is still unknown. It is exhaustive and time consuming to test in vitro all chemicals - potential EDCs - used in industry, agriculture or as food preservatives against their effects on the endocrine system. Computational methods, such as virtual screening, quantitative structure activity relationships and docking, are already well recognized and used in drug development. The same methods could also aid the research on EDCs. So far, the computational methods in the search of EDCs have been retrospective. There are, however, some prospective studies reporting the use of in silico methods: five studies reporting the identification of previously unknown 17β-HSD3 inhibitors, MR agonists, and ER antagonists/agonists. This review provides an overview of case studies and in silico methods that are used in the search of EDCs. This article is part of a Special Issue entitled 'CSR 2013'.

Planta Medica, 2012

The natural quinone compounds are produced by a number of plants, fungi, and also by animals. Som... more The natural quinone compounds are produced by a number of plants, fungi, and also by animals. Some of them found application in industry as colorants and in medicine as laxatives. However, natural quinone compounds also exert other various biological (particularly antibacterial, fungicidal, and cytotoxic) effects including anti-inflammatory activity [1-3]. As the best examples can be mentioned diacerein and its active metabolite rhein, the anthraquinones with interleukine-1β inhibitory activity used as symptomatic, slowacting drugs in osteoarthritis . The naphthoquinones shikonin and alkannin as well as the benzoquinone thymoquinone exhibit in vivo anti-inflammatory activity when administered to rats . It has been shown that thymoquinone is able to inhibit catalytic activity of cyclooxygenase-1 (COX-1) and -2 (COX-2) in our previous study . However, no systematic study on quinones and their derivatives regarding their COXinhibiting activity and mechanism of action has been reported yet.

Journal of Chemical Information and Modeling, 2007

Parallel Screening has been introduced as an in silico method to predict the potential biological... more Parallel Screening has been introduced as an in silico method to predict the potential biological activities of compounds by screening them with a multitude of pharmacophore models. This study presents an early application example employing a Pipeline Pilot-based screening platform for automatic large-scale virtual activity profiling. An extensive set of HIV protease inhibitor pharmacophore models was used to screen a selection of active and inactive compounds. Furthermore, we aimed to address the usually critically eyed point, whether it is possible in a parallel screening system to differentiate between similar molecules/molecules acting on closely related proteins, and therefore we incorporated a collection of other protease inhibitors including aspartic protease inhibitors. The results of the screening experiments show a clear trend toward most extensive retrieval of known active ligands, followed by the general protease inhibitors and lowest recovery of inactive compounds.

Journal of Chemical Information and Modeling, 2012

Liver X receptors (LXRs) are members of the nuclear receptor family. Activators of LXRs are of hi... more Liver X receptors (LXRs) are members of the nuclear receptor family. Activators of LXRs are of high pharmacological interest as LXRs regulate cholesterol, fatty acid, and carbohydrate metabolism as well as inflammatory processes. On the basis of different X-ray crystal structures, we established a virtual screening workflow for the identification of novel LXR modulators. A two-step screening concept to identify active compounds included 3D-pharmacophore filters and rescoring by shape alignment. Eighteen virtual hits were tested in vitro applying a reporter gene assay, where concentration-dependent activity was proven for four novel lead structures. The most active compound 10, a 1,4-naphthochinone, has an estimated EC₅₀ of around 5 μM.

Bioorganic & Medicinal Chemistry Letters, 2012

The release of arachidonic acid, a precursor in the production of prostaglandins and leukotrienes... more The release of arachidonic acid, a precursor in the production of prostaglandins and leukotrienes, is achieved by activity of the cytosolic phospholipase A 2 a (cPLA 2 a). Signaling mediated by this class of bioactive lipids, which are collectively referred to as eicosanoids, has numerous effects in physiological and pathological processes. Herein, we report the development of a ligand-based pharmacophore model and pharmacophore-based virtual screening of the National Cancer Institute (NCI) database, leading to the identification of 4-(hexadecyloxy)-3-(2-(hydroxyimino)-3-oxobutanamido)benzoic acid (NSC 119957) as cPLA 2 a inhibitor in cell-free and cell-based in vitro assays.

Bioorganic & Medicinal Chemistry, 2010

The inhibition of 11b-hydroxysteroid dehydrogenase 1 (11b-HSD1), which catalyzes the conversion o... more The inhibition of 11b-hydroxysteroid dehydrogenase 1 (11b-HSD1), which catalyzes the conversion of inactive 11-ketoglucocorticoids to active 11b-hydroxyglucocorticoids, emerged as promising strategy to treat symptoms of the metabolic syndrome, including obesity and type 2 diabetes. In this study the leaves of the anti-diabetic medicinal plant loquat (Eriobotrya japonica) were phytochemically investigated following hints from a pharmacophore-based virtual screening and a bioactivity-guided approach. Determination of the 11b-HSD1 and 11b-HSD2 inhibitory activities in cell lysates revealed triterpenes from the ursane type as selective, low micro-molar inhibitors of 11b-HSD1, that is, corosolic acid (1), 3-epicorosolic acid methyl ester (4), 2-a hydroxy-3-oxo urs-12-en-28-oic acid (6), tormentic acid methyl ester (8), and ursolic acid (9). Importantly, a mixture of loquat constituents with moderate activities displayed a pronounced additive effect. By means of molecular modeling studies and the identification of the 11b-HSD1-inhibiting 11-keto-ursolic acid (17) and 3-acetyl-11-keto-ursolic acid (18) a structure-activity relationship was deduced for this group of pentacyclic triterpenes. The mechanism of action elucidated in the present work together with the previously determined pharmacological activities provides these natural products with an astonishing multi-targeted anti-diabetic profile.

Bioorganic & Medicinal Chemistry Letters, 2013

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.

Bioorganic Medicinal Chemistry, Feb 15, 2010

The inhibition of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1), which catalyzes the conver... more The inhibition of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1), which catalyzes the conversion of inactive 11-ketoglucocorticoids to active 11beta-hydroxyglucocorticoids, emerged as promising strategy to treat symptoms of the metabolic syndrome, including obesity and type 2 diabetes. In this study the leaves of the anti-diabetic medicinal plant loquat (Eriobotrya japonica) were phytochemically investigated following hints from a pharmacophore-based virtual screening and a bioactivity-guided approach. Determination of the 11beta-HSD1 and 11beta-HSD2 inhibitory activities in cell lysates revealed triterpenes from the ursane type as selective, low micro-molar inhibitors of 11beta-HSD1, that is, corosolic acid (1), 3-epicorosolic acid methyl ester (4), 2-alpha hydroxy-3-oxo urs-12-en-28-oic acid (6), tormentic acid methyl ester (8), and ursolic acid (9). Importantly, a mixture of loquat constituents with moderate activities displayed a pronounced additive effect. By means of molecular modeling studies and the identification of the 11beta-HSD1-inhibiting 11-keto-ursolic acid (17) and 3-acetyl-11-keto-ursolic acid (18) a structure-activity relationship was deduced for this group of pentacyclic triterpenes. The mechanism of action elucidated in the present work together with the previously determined pharmacological activities provides these natural products with an astonishing multi-targeted anti-diabetic profile.

Toxicological Sciences, 2012

Anabolic androgenic steroids (AAS) are testosterone derivatives used either clinically, in elite ... more Anabolic androgenic steroids (AAS) are testosterone derivatives used either clinically, in elite sports, or for body shaping with the goal to increase muscle size and strength. Clinically developed compounds and nonclinically tested designer steroids often marketed as food supplements are widely used. Despite the considerable evidence for various adverse effects of AAS use, the underlying molecular mechanisms are insufficiently understood. Here, we investigated whether some AAS, as a result of a lack of target selectivity, might inhibit 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2)-dependent inactivation of glucocorticoids. Using recombinant human 11β-HSD2, we observed inhibitory effects for several AAS. Whereas oxymetholone, oxymesterone, danazol, and testosterone showed medium inhibitory potential, fluoxymesterone was a potent inhibitor of human 11β-HSD2 (half-maximal inhibitory concentration [IC(50)] of 60-100nM in cell lysates; IC(50) of 160nM in intact SW-620, and 530nM in MCF-7 cells). Measurements with rat kidney microsomes and lysates of cells expressing recombinant mouse 11β-HSD2 revealed much weaker inhibition by the AAS tested, indicating that the adverse effects of AAS-dependent 11β-HSD2 inhibition cannot be investigated in rats and mice. Furthermore, we provide evidence that fluoxymesterone is metabolized to 11-oxofluoxymesterone by human 11β-HSD2. Structural modeling revealed similar binding modes for fluoxymesterone and cortisol, supporting a competitive mode of inhibition of 11β-HSD2-dependent cortisol oxidation by this AAS. No direct modulation of mineralocorticoid receptor (MR) function was observed. Thus, 11β-HSD2 inhibition by fluoxymesterone may cause cortisol-induced MR activation, thereby leading to electrolyte disturbances and contributing to the development of hypertension and cardiovascular disease.

The Journal of Steroid Biochemistry and Molecular Biology, 2011

Modulation of intracellular glucocorticoid availability is considered as a promising strategy to ... more Modulation of intracellular glucocorticoid availability is considered as a promising strategy to treat glucocorticoid-dependent diseases. 18␤-Glycyrrhetinic acid (GA), the biologically active triterpenoid metabolite of glycyrrhizin, which is contained in the roots and rhizomes of licorice (Glycyrrhiza spp.), represents a well-known but non-selective inhibitor of 11␤-hydroxysteroid dehydrogenases (11␤-HSDs). However, to assess the physiological functions of the respective enzymes and for potential therapeutic applications selective inhibitors are needed. In the present study, we applied bioassays and 3D-structure modeling to characterize nine 11␤-HSD1 and fifteen 11␤-HSD2 inhibiting GA derivatives. Comparison of the GA derivatives in assays using cell lysates revealed that modifications at the 3-hydroxyl and/or the carboxyl led to highly selective and potent 11␤-HSD2 inhibitors. The data generated significantly extends our knowledge on structure-activity relationship of GA derivatives as 11␤-HSD inhibitors. Using recombinant enzymes we found also potent inhibition of mouse 11␤-HSD2, despite significant species-specific differences. The selected GA derivatives potently inhibited 11␤-HSD2 in intact SW-620 colon cancer cells, although the rank order of inhibitory potential differed from that obtained in cell lysates. The biological activity of compounds was further demonstrated in glucocorticoid receptor (GR) transactivation assays in cells coexpressing GR and 11␤-HSD1 or 11␤-HSD2. 3D-structure modeling provides an explanation for the differences in the selectivity and activity of the GA derivatives investigated. The most potent and selective 11␤-HSD2 inhibitors should prove useful as mechanistic tools for further anti-inflammatory and anti-cancer in vitro and in vivo studies.

Modulation of intracellular glucocorticoid availability is considered as a promising strategy to ... more Modulation of intracellular glucocorticoid availability is considered as a promising strategy to treat glucocorticoid-dependent diseases. 18␤-Glycyrrhetinic acid (GA), the biologically active triterpenoid metabolite of glycyrrhizin, which is contained in the roots and rhizomes of licorice (Glycyrrhiza spp.), represents a well-known but non-selective inhibitor of 11␤-hydroxysteroid dehydrogenases (11␤-HSDs). However, to assess the physiological functions of the respective enzymes and for potential therapeutic applications selective inhibitors are needed. In the present study, we applied bioassays and 3D-structure modeling to characterize nine 11␤-HSD1 and fifteen 11␤-HSD2 inhibiting GA derivatives. Comparison of the GA derivatives in assays using cell lysates revealed that modifications at the 3-hydroxyl and/or the carboxyl led to highly selective and potent 11␤-HSD2 inhibitors. The data generated significantly extends our knowledge on structure-activity relationship of GA derivatives as 11␤-HSD inhibitors. Using recombinant enzymes we found also potent inhibition of mouse 11␤-HSD2, despite significant species-specific differences. The selected GA derivatives potently inhibited 11␤-HSD2 in intact SW-620 colon cancer cells, although the rank order of inhibitory potential differed from that obtained in cell lysates. The biological activity of compounds was further demonstrated in glucocorticoid receptor (GR) transactivation assays in cells coexpressing GR and 11␤-HSD1 or 11␤-HSD2. 3D-structure modeling provides an explanation for the differences in the selectivity and activity of the GA derivatives investigated. The most potent and selective 11␤-HSD2 inhibitors should prove useful as mechanistic tools for further anti-inflammatory and anti-cancer in vitro and in vivo studies.

Biotechnology Advances, 2015

Journal of Agricultural and Food Chemistry, 2015

Blockage of the human ether-à-go-go related gene (hERG) channel can result in life-threatening ve... more Blockage of the human ether-à-go-go related gene (hERG) channel can result in life-threatening ventricular tachyarrhythmia. In an in vitro screening of herbal materials for hERG blockers using an automated two-microelectrode voltage clamp assay on Xenopus oocytes, an alkaloid fraction of Nelumbo nucifera Gaertn. (lotus) leaves induced ∼50% of hERG current inhibition at 100 μg/mL. Chromatographic separation resulted in the isolation and identification of (-)-asimilobine, 1, nuciferine, 2, O-nornuciferine, 3, N-nornuciferine, 4, and liensinine, 5. In agreement with in silico predicted ligand-target interactions, 2, 3, and 4 revealed distinct in vitro hERG blockages measured in HEK293 cells with IC50 values of 2.89, 7.91, and 9.75 μM, respectively. Because lotus leaf dietary weight loss supplements are becoming increasingly popular, the identified hERG-blocking alkaloids were quantitated in five commercially available products. Results showed pronounced differences in the content of hERG-blocking alkaloids ranging up to 992 μg (2) in the daily recommended dose.

Scripta Materialia, 2002

In a 2650-T8 aluminium, the initial bi-modal homogeneous precipitation (GPB fine needles and S′ p... more In a 2650-T8 aluminium, the initial bi-modal homogeneous precipitation (GPB fine needles and S′ precipitates) evolves during a thermal exposure at 150 °C: the GPB fine needles disappear. This dissolution is accelerated by creep and leads to a loss of mechanical resistance.

Phytochemistry, Jan 6, 2014

The species complex around the medicinal fungus Ganoderma lucidum Karst. (Ganodermataceae) is wid... more The species complex around the medicinal fungus Ganoderma lucidum Karst. (Ganodermataceae) is widely known in traditional medicines, as well as in modern applications such as functional food or nutraceuticals. A considerable number of publications reflects its abundance and variety in biological actions either provoked by primary metabolites, such as polysaccharides, or secondary metabolites, such as lanostane-type triterpenes. However, due to this remarkable amount of information, a rationalization of the individual Ganoderma constituents to biological actions on a molecular level is quite challenging. To overcome this issue, a database was generated containing meta-information, i.e., chemical structures and biological actions of hitherto identified Ganoderma constituents (279). This was followed by a computational approach subjecting this 3D multi-conformational molecular dataset to in silico parallel screening against an in-house collection of validated structure- and ligand-base...

Mediators of inflammation, 2014

Cyclooxygenases and lipoxygenases are proinflammatory enzymes; the former affects platelet aggreg... more Cyclooxygenases and lipoxygenases are proinflammatory enzymes; the former affects platelet aggregation, vasoconstriction, vasodilatation and later the development of atherosclerosis. Red wines from Georgia and central and western Europe inhibited cyclooxygenase-1 (COX-1) activity in the range of 63-94%, cyclooxygenase-2 (COX-2) activity in the range of 20-44% (tested at a concentration of 5 mL/L), and 5-lipoxygenase (5-LOX) activity in the range of 72-84% (at a concentration of 18.87 mL/L). White wines inhibited 5-LOX in the range of 41-68% at a concentration of 18.87 mL/L and did not inhibit COX-1 and COX-2. Piceatannol (IC 50 = 0.76 M) was identified as a strong inhibitor of 5-LOX followed by luteolin (IC 50 = 2.25 M), quercetin (IC 50 = 3.29 M), and myricetin (IC 50 = 4.02 M). trans-Resveratrol was identified as an inhibitor of COX-1 (IC 50 = 2.27 M) and COX-2 (IC 50 = 3.40 M). Red wine as a complex mixture is a powerful inhibitor of COX-1, COX-2, and 5-LOX, the enzymes involved in eicosanoid biosynthetic pathway.

European Journal of Medicinal Chemistry, 2015

Several new 4-phenylpyrimidine-2(1H)-thiones have been prepared and investigated for their potenc... more Several new 4-phenylpyrimidine-2(1H)-thiones have been prepared and investigated for their potencies to inhibit COX-1 and COX-2 enzymes, and COX-2 expression in THP-1 cells. Structure-activity-relationships and physicochemical parameters are discussed. Pharmacophore screening and docking studies were carried out for the most active compound.

The Journal of Steroid Biochemistry and Molecular Biology, 2013

The prevalence of sex hormone-dependent cancers, reproductive problems, obesity, and cardiovascul... more The prevalence of sex hormone-dependent cancers, reproductive problems, obesity, and cardiovascular complications has risen especially in the Western world. It has been suggested, that the exposure to various endocrine disrupting chemicals (EDCs) contributes to the development and progression of these diseases. EDCs can interfere with various proteins: nuclear steroid hormone receptors, such as estrogen-, androgen-, glucocorticoid- and mineralocorticoid receptors (ER, AR, GR, MR), and enzymes that are involved in steroid hormone synthesis and metabolism, for example hydroxysteroid dehydrogenases (HSDs). Numerous chemicals are known as endocrine disruptors. However, the mechanism of action for most of these EDCs is still unknown. It is exhaustive and time consuming to test in vitro all chemicals - potential EDCs - used in industry, agriculture or as food preservatives against their effects on the endocrine system. Computational methods, such as virtual screening, quantitative structure activity relationships and docking, are already well recognized and used in drug development. The same methods could also aid the research on EDCs. So far, the computational methods in the search of EDCs have been retrospective. There are, however, some prospective studies reporting the use of in silico methods: five studies reporting the identification of previously unknown 17β-HSD3 inhibitors, MR agonists, and ER antagonists/agonists. This review provides an overview of case studies and in silico methods that are used in the search of EDCs. This article is part of a Special Issue entitled 'CSR 2013'.

Planta Medica, 2012

The natural quinone compounds are produced by a number of plants, fungi, and also by animals. Som... more The natural quinone compounds are produced by a number of plants, fungi, and also by animals. Some of them found application in industry as colorants and in medicine as laxatives. However, natural quinone compounds also exert other various biological (particularly antibacterial, fungicidal, and cytotoxic) effects including anti-inflammatory activity [1-3]. As the best examples can be mentioned diacerein and its active metabolite rhein, the anthraquinones with interleukine-1β inhibitory activity used as symptomatic, slowacting drugs in osteoarthritis . The naphthoquinones shikonin and alkannin as well as the benzoquinone thymoquinone exhibit in vivo anti-inflammatory activity when administered to rats . It has been shown that thymoquinone is able to inhibit catalytic activity of cyclooxygenase-1 (COX-1) and -2 (COX-2) in our previous study . However, no systematic study on quinones and their derivatives regarding their COXinhibiting activity and mechanism of action has been reported yet.

Journal of Chemical Information and Modeling, 2007

Parallel Screening has been introduced as an in silico method to predict the potential biological... more Parallel Screening has been introduced as an in silico method to predict the potential biological activities of compounds by screening them with a multitude of pharmacophore models. This study presents an early application example employing a Pipeline Pilot-based screening platform for automatic large-scale virtual activity profiling. An extensive set of HIV protease inhibitor pharmacophore models was used to screen a selection of active and inactive compounds. Furthermore, we aimed to address the usually critically eyed point, whether it is possible in a parallel screening system to differentiate between similar molecules/molecules acting on closely related proteins, and therefore we incorporated a collection of other protease inhibitors including aspartic protease inhibitors. The results of the screening experiments show a clear trend toward most extensive retrieval of known active ligands, followed by the general protease inhibitors and lowest recovery of inactive compounds.

Journal of Chemical Information and Modeling, 2012

Liver X receptors (LXRs) are members of the nuclear receptor family. Activators of LXRs are of hi... more Liver X receptors (LXRs) are members of the nuclear receptor family. Activators of LXRs are of high pharmacological interest as LXRs regulate cholesterol, fatty acid, and carbohydrate metabolism as well as inflammatory processes. On the basis of different X-ray crystal structures, we established a virtual screening workflow for the identification of novel LXR modulators. A two-step screening concept to identify active compounds included 3D-pharmacophore filters and rescoring by shape alignment. Eighteen virtual hits were tested in vitro applying a reporter gene assay, where concentration-dependent activity was proven for four novel lead structures. The most active compound 10, a 1,4-naphthochinone, has an estimated EC₅₀ of around 5 μM.

Bioorganic & Medicinal Chemistry Letters, 2012

The release of arachidonic acid, a precursor in the production of prostaglandins and leukotrienes... more The release of arachidonic acid, a precursor in the production of prostaglandins and leukotrienes, is achieved by activity of the cytosolic phospholipase A 2 a (cPLA 2 a). Signaling mediated by this class of bioactive lipids, which are collectively referred to as eicosanoids, has numerous effects in physiological and pathological processes. Herein, we report the development of a ligand-based pharmacophore model and pharmacophore-based virtual screening of the National Cancer Institute (NCI) database, leading to the identification of 4-(hexadecyloxy)-3-(2-(hydroxyimino)-3-oxobutanamido)benzoic acid (NSC 119957) as cPLA 2 a inhibitor in cell-free and cell-based in vitro assays.

Bioorganic & Medicinal Chemistry, 2010

The inhibition of 11b-hydroxysteroid dehydrogenase 1 (11b-HSD1), which catalyzes the conversion o... more The inhibition of 11b-hydroxysteroid dehydrogenase 1 (11b-HSD1), which catalyzes the conversion of inactive 11-ketoglucocorticoids to active 11b-hydroxyglucocorticoids, emerged as promising strategy to treat symptoms of the metabolic syndrome, including obesity and type 2 diabetes. In this study the leaves of the anti-diabetic medicinal plant loquat (Eriobotrya japonica) were phytochemically investigated following hints from a pharmacophore-based virtual screening and a bioactivity-guided approach. Determination of the 11b-HSD1 and 11b-HSD2 inhibitory activities in cell lysates revealed triterpenes from the ursane type as selective, low micro-molar inhibitors of 11b-HSD1, that is, corosolic acid (1), 3-epicorosolic acid methyl ester (4), 2-a hydroxy-3-oxo urs-12-en-28-oic acid (6), tormentic acid methyl ester (8), and ursolic acid (9). Importantly, a mixture of loquat constituents with moderate activities displayed a pronounced additive effect. By means of molecular modeling studies and the identification of the 11b-HSD1-inhibiting 11-keto-ursolic acid (17) and 3-acetyl-11-keto-ursolic acid (18) a structure-activity relationship was deduced for this group of pentacyclic triterpenes. The mechanism of action elucidated in the present work together with the previously determined pharmacological activities provides these natural products with an astonishing multi-targeted anti-diabetic profile.

Bioorganic & Medicinal Chemistry Letters, 2013

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.

Bioorganic Medicinal Chemistry, Feb 15, 2010

The inhibition of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1), which catalyzes the conver... more The inhibition of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1), which catalyzes the conversion of inactive 11-ketoglucocorticoids to active 11beta-hydroxyglucocorticoids, emerged as promising strategy to treat symptoms of the metabolic syndrome, including obesity and type 2 diabetes. In this study the leaves of the anti-diabetic medicinal plant loquat (Eriobotrya japonica) were phytochemically investigated following hints from a pharmacophore-based virtual screening and a bioactivity-guided approach. Determination of the 11beta-HSD1 and 11beta-HSD2 inhibitory activities in cell lysates revealed triterpenes from the ursane type as selective, low micro-molar inhibitors of 11beta-HSD1, that is, corosolic acid (1), 3-epicorosolic acid methyl ester (4), 2-alpha hydroxy-3-oxo urs-12-en-28-oic acid (6), tormentic acid methyl ester (8), and ursolic acid (9). Importantly, a mixture of loquat constituents with moderate activities displayed a pronounced additive effect. By means of molecular modeling studies and the identification of the 11beta-HSD1-inhibiting 11-keto-ursolic acid (17) and 3-acetyl-11-keto-ursolic acid (18) a structure-activity relationship was deduced for this group of pentacyclic triterpenes. The mechanism of action elucidated in the present work together with the previously determined pharmacological activities provides these natural products with an astonishing multi-targeted anti-diabetic profile.

Toxicological Sciences, 2012

Anabolic androgenic steroids (AAS) are testosterone derivatives used either clinically, in elite ... more Anabolic androgenic steroids (AAS) are testosterone derivatives used either clinically, in elite sports, or for body shaping with the goal to increase muscle size and strength. Clinically developed compounds and nonclinically tested designer steroids often marketed as food supplements are widely used. Despite the considerable evidence for various adverse effects of AAS use, the underlying molecular mechanisms are insufficiently understood. Here, we investigated whether some AAS, as a result of a lack of target selectivity, might inhibit 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2)-dependent inactivation of glucocorticoids. Using recombinant human 11β-HSD2, we observed inhibitory effects for several AAS. Whereas oxymetholone, oxymesterone, danazol, and testosterone showed medium inhibitory potential, fluoxymesterone was a potent inhibitor of human 11β-HSD2 (half-maximal inhibitory concentration [IC(50)] of 60-100nM in cell lysates; IC(50) of 160nM in intact SW-620, and 530nM in MCF-7 cells). Measurements with rat kidney microsomes and lysates of cells expressing recombinant mouse 11β-HSD2 revealed much weaker inhibition by the AAS tested, indicating that the adverse effects of AAS-dependent 11β-HSD2 inhibition cannot be investigated in rats and mice. Furthermore, we provide evidence that fluoxymesterone is metabolized to 11-oxofluoxymesterone by human 11β-HSD2. Structural modeling revealed similar binding modes for fluoxymesterone and cortisol, supporting a competitive mode of inhibition of 11β-HSD2-dependent cortisol oxidation by this AAS. No direct modulation of mineralocorticoid receptor (MR) function was observed. Thus, 11β-HSD2 inhibition by fluoxymesterone may cause cortisol-induced MR activation, thereby leading to electrolyte disturbances and contributing to the development of hypertension and cardiovascular disease.

The Journal of Steroid Biochemistry and Molecular Biology, 2011

Modulation of intracellular glucocorticoid availability is considered as a promising strategy to ... more Modulation of intracellular glucocorticoid availability is considered as a promising strategy to treat glucocorticoid-dependent diseases. 18␤-Glycyrrhetinic acid (GA), the biologically active triterpenoid metabolite of glycyrrhizin, which is contained in the roots and rhizomes of licorice (Glycyrrhiza spp.), represents a well-known but non-selective inhibitor of 11␤-hydroxysteroid dehydrogenases (11␤-HSDs). However, to assess the physiological functions of the respective enzymes and for potential therapeutic applications selective inhibitors are needed. In the present study, we applied bioassays and 3D-structure modeling to characterize nine 11␤-HSD1 and fifteen 11␤-HSD2 inhibiting GA derivatives. Comparison of the GA derivatives in assays using cell lysates revealed that modifications at the 3-hydroxyl and/or the carboxyl led to highly selective and potent 11␤-HSD2 inhibitors. The data generated significantly extends our knowledge on structure-activity relationship of GA derivatives as 11␤-HSD inhibitors. Using recombinant enzymes we found also potent inhibition of mouse 11␤-HSD2, despite significant species-specific differences. The selected GA derivatives potently inhibited 11␤-HSD2 in intact SW-620 colon cancer cells, although the rank order of inhibitory potential differed from that obtained in cell lysates. The biological activity of compounds was further demonstrated in glucocorticoid receptor (GR) transactivation assays in cells coexpressing GR and 11␤-HSD1 or 11␤-HSD2. 3D-structure modeling provides an explanation for the differences in the selectivity and activity of the GA derivatives investigated. The most potent and selective 11␤-HSD2 inhibitors should prove useful as mechanistic tools for further anti-inflammatory and anti-cancer in vitro and in vivo studies.

Modulation of intracellular glucocorticoid availability is considered as a promising strategy to ... more Modulation of intracellular glucocorticoid availability is considered as a promising strategy to treat glucocorticoid-dependent diseases. 18␤-Glycyrrhetinic acid (GA), the biologically active triterpenoid metabolite of glycyrrhizin, which is contained in the roots and rhizomes of licorice (Glycyrrhiza spp.), represents a well-known but non-selective inhibitor of 11␤-hydroxysteroid dehydrogenases (11␤-HSDs). However, to assess the physiological functions of the respective enzymes and for potential therapeutic applications selective inhibitors are needed. In the present study, we applied bioassays and 3D-structure modeling to characterize nine 11␤-HSD1 and fifteen 11␤-HSD2 inhibiting GA derivatives. Comparison of the GA derivatives in assays using cell lysates revealed that modifications at the 3-hydroxyl and/or the carboxyl led to highly selective and potent 11␤-HSD2 inhibitors. The data generated significantly extends our knowledge on structure-activity relationship of GA derivatives as 11␤-HSD inhibitors. Using recombinant enzymes we found also potent inhibition of mouse 11␤-HSD2, despite significant species-specific differences. The selected GA derivatives potently inhibited 11␤-HSD2 in intact SW-620 colon cancer cells, although the rank order of inhibitory potential differed from that obtained in cell lysates. The biological activity of compounds was further demonstrated in glucocorticoid receptor (GR) transactivation assays in cells coexpressing GR and 11␤-HSD1 or 11␤-HSD2. 3D-structure modeling provides an explanation for the differences in the selectivity and activity of the GA derivatives investigated. The most potent and selective 11␤-HSD2 inhibitors should prove useful as mechanistic tools for further anti-inflammatory and anti-cancer in vitro and in vivo studies.

Biotechnology Advances, 2015

Journal of Agricultural and Food Chemistry, 2015

Blockage of the human ether-à-go-go related gene (hERG) channel can result in life-threatening ve... more Blockage of the human ether-à-go-go related gene (hERG) channel can result in life-threatening ventricular tachyarrhythmia. In an in vitro screening of herbal materials for hERG blockers using an automated two-microelectrode voltage clamp assay on Xenopus oocytes, an alkaloid fraction of Nelumbo nucifera Gaertn. (lotus) leaves induced ∼50% of hERG current inhibition at 100 μg/mL. Chromatographic separation resulted in the isolation and identification of (-)-asimilobine, 1, nuciferine, 2, O-nornuciferine, 3, N-nornuciferine, 4, and liensinine, 5. In agreement with in silico predicted ligand-target interactions, 2, 3, and 4 revealed distinct in vitro hERG blockages measured in HEK293 cells with IC50 values of 2.89, 7.91, and 9.75 μM, respectively. Because lotus leaf dietary weight loss supplements are becoming increasingly popular, the identified hERG-blocking alkaloids were quantitated in five commercially available products. Results showed pronounced differences in the content of hERG-blocking alkaloids ranging up to 992 μg (2) in the daily recommended dose.

Scripta Materialia, 2002

In a 2650-T8 aluminium, the initial bi-modal homogeneous precipitation (GPB fine needles and S′ p... more In a 2650-T8 aluminium, the initial bi-modal homogeneous precipitation (GPB fine needles and S′ precipitates) evolves during a thermal exposure at 150 °C: the GPB fine needles disappear. This dissolution is accelerated by creep and leads to a loss of mechanical resistance.

Phytochemistry, Jan 6, 2014

The species complex around the medicinal fungus Ganoderma lucidum Karst. (Ganodermataceae) is wid... more The species complex around the medicinal fungus Ganoderma lucidum Karst. (Ganodermataceae) is widely known in traditional medicines, as well as in modern applications such as functional food or nutraceuticals. A considerable number of publications reflects its abundance and variety in biological actions either provoked by primary metabolites, such as polysaccharides, or secondary metabolites, such as lanostane-type triterpenes. However, due to this remarkable amount of information, a rationalization of the individual Ganoderma constituents to biological actions on a molecular level is quite challenging. To overcome this issue, a database was generated containing meta-information, i.e., chemical structures and biological actions of hitherto identified Ganoderma constituents (279). This was followed by a computational approach subjecting this 3D multi-conformational molecular dataset to in silico parallel screening against an in-house collection of validated structure- and ligand-base...