Novel mannosylerythritol lipid biosurfactant structures from castor oil revealed by advanced structure analysis.

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by fungi of the Ustilaginaceae family in the presence of hydrophobic carbon sources like plant oils. In the present study, we investigated the structural composition of MELs produced from castor oil using seven different microorganisms and compared them to MEL structures resulting from other plant oils. Castor oil is an industrially relevant plant oil that presents as an alternative to currently employed edible plant oils like rapeseed or soybean oil. The main fatty acid in castor oil is the mono-hydroxylated ricinoleic acid, providing the possibility to produce novel MEL structures with interesting features. Analysis of the produced MELs from castor oil by different chromatographic and mass spectrometry techniques revealed that all seven microorganisms were generally able to integrate hydroxylated fatty acids into the MEL molecule, although at varying degrees. These novel MELs containing a hydroxy fatty acid (4-O-[2'-O-alka(e)noyl-3'-O-hydroxyalka(e)noyl-4'/6'-O-acetyl-ß-D-mannopyranosyl]-erythritol) were more hydrophilic than conventional MEL and therefore showed a different elution behavior in chromatography. Large shares of novel hydroxy MELs (around 50% of total MELs) were found for the two MEL-B/C producing species Ustilago siamensis and Ustilago shanxiensis, but also for the MEL-A/B/C producer Moesziomyces aphidis (around 25%). In addition, tri-acylated hydroxylated MELs with a third long-chain fatty acid esterified to the free hydroxyl group of the hydroxy fatty acid were identified for some species. Overall, production of MEL from castor oil with the investigated organisms provided a complex mixture of various novel MEL structures that can be exploited for further research.

Structure-Based Design of Potent Selective Nanomolar Type-II Inhibitors of Glycogen Synthase Kinase-3ß.

For the first time, the in silico design, screening, and in vitro validation of potent GSK-3ß type-II inhibitors are presented. In the absence of crystallographic evidence for a DFG-out GSK-3ß activation loop conformation, computational models were designed using an adapted DOLPHIN approach and a method consisting of Prime loop refinement, induced-fit docking, and molecular dynamics. Virtual screening of the Biogenics subset from the ZINC database led to an initial selection of 20 Phase I compounds revealing two low micromolar inhibitors in an isolated enzyme assay. Twenty more analogues (Phase II compounds) related to the hit [pyrimidin-2-yl]amino-furo[3,2-b]furyl-urea scaffold were selected for structure-activity relationship analysis. The Phase II studies led to five highly potent nanomolar inhibitors, with compound 23 (IC50 =0.087 µM) > 100 times more potent than the best Phase I inhibitor, and selectivity for GSK-3ß inhibition compared to homologous kinases was observed. Ex vivo experiments (SH-SY5Y cell lines) for tau hyperphosphorylation revealed promising neuroprotective effects at low micromolar concentrations. The type-II inhibitor design has been unraveled as a potential route toward more clinically effective GSK-3ß inhibitors.

MacroEvoLution: A New Method for the Rapid Generation of Novel Scaffold-Diverse Macrocyclic Libraries.

Macrocycles are a structural class bearing great promise for future challenges in medicinal chemistry. Nevertheless, there are few flexible approaches for the rapid generation of structurally diverse macrocyclic compound collections. Here, an efficient method for the generation of novel macrocyclic peptide-based scaffolds is reported. The process, named here as "MacroEvoLution", is based on a cyclization screening approach that gives reliable access to novel macrocyclic architectures. Classification of building blocks into specific pools ensures that scaffolds with orthogonally addressable functionalities are generated, which can easily be used for the generation of structurally diverse compound libraries. The method grants rapid access to novel scaffolds with scalable synthesis (multi gram scale) and the introduction of further diversity at a late stage. Despite being developed for peptidic systems, the approach can easily be extended for the synthesis of systems with a decreased peptidic character.

Chemical composition and biological activity of Paris quadrifolia L.

A study of the components of Paris quadrifolia was undertaken to identify compounds with potential influence on cardiac cells, since previous reports suggested a cardiotoxic risk of this plant. Compounds isolated and identified included one new steroidal saponin, (23S,24S)-spirosta-5,25(27)-diene-1beta,3beta,21,23,24-pentol-1-O-beta-D-apiofuranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-glucopyranoside 21-O-beta-D-apiofuranoside 24-O-beta-D-fucopyranoside (1), demonstrating quite unusual structural features, as well as the known compounds 26-O-beta-D-glucopyranosyl-(25R)-5-en-furost-3beta,17alpha,22alpha,26-tetraol-3-O-alpha-L-rhamnopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->4)-[alpha-L-rhamnopyranosyl--(1-->2)]-beta-D-glucopyranoside (2), pennogenin 3-O-alpha-L-rhamnopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->4)-[alpha-L-rhamnopyranosyl-(1-->2)]-beta-D-glucopyranoside (3), 7-O-beta-D-glucopyranosyl-kaempferol-3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-galactopyranoside (4), kaempferol-3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-galactopyranoside (5), 5-hydroxyecdysterone (6), and 20-hydroxyecdysone (7). The pennogenin derivative 3 showed strong cardiotoxic effects in an in vitro cellular model system, whereas the respective furostanol derivative 2 was inactive.

Natural products in parallel chemistry--novel 5-lipoxygenase inhibitors from BIOS-based libraries starting from alpha-santonin.

Recently, we developed a concept known as biology-oriented synthesis (BIOS), which targets the design and synthesis of small- to medium-sized compound libraries on the basis of genuine natural product templates to provide screening compounds with high biological relevance. We herein describe the parallel solution phase synthesis of two BIOS-based libraries starting from alpha-santonin (1). Modification of the sesquiterpene lactone 1 by introduction of a thiazole moiety followed by a Lewis-acid-mediated lactone opening yielded a first library of natural product analogues. An acid-mediated dienone-phenol rearrangement of 1 and a subsequent etherification/amidation sequence led to a second natural product-based library. After application of a fingerprint-based virtual screening on these compounds, the biological screening of 23 selected library members against 5-lipoxygenase resulted in the discovery of four potent novel inhibitors of this enzyme.

Identification of inhibitors for mycobacterial protein tyrosine phosphatase B (MptpB) by biology-oriented synthesis (BIOS).

Protein phosphatases have recently emerged as important targets for research in chemical biology and medicinal chemistry, and new classes of phosphatase inhibitors are in high demand. BIOS (biology-oriented synthesis) employs the criteria of relevance to nature and biological prevalidation for the design and synthesis of compound collections. In an application of the BIOS principle, an efficient solid-phase synthesis of highly substituted indolo[2,3-a]quinolizidines by using a vinylogous Mannich-Michael reaction in combination with phosgene- or acid-mediated ring closure was developed. Screening of this library for phosphatase inhibitors yielded a new inhibitor class for the Mycobacterium tuberculosis phosphatase MptpB.

Natural products in combinatorial chemistry: an andrographolide-based library.

The generation of a natural-product-based library starting from andrographolide is described. Utilizing andrographolide itself in parallel solution-phase synthesis leads to a 360-membered library. The initial transformation of the starting material via ozonolysis is followed by the conversion into a suitable template by introduction of a thiazole moiety. Subsequent decoration at two points of diversity yields the desired natural product derivatives. The selection of actually synthesized compounds is based on a virtually generated library and the assessment of its members with respect to physicochemical parameters, thus ensuring pharmacological relevance of the compounds.