EVALUATION OF POMEGRANATE PEEL AS A SUBSTRATE FOR CITRIC ACID PRODUCTION BY ASPERGILLUS NIGER

Objective: The present study aimed to evaluate dried pomegranate peels as a substrate for citric acid production by Aspergillus niger. Methods: The morphological study of Aspergillus niger was carried out by wet mount with lactophenol cotton blue and slide culture method. A preliminary qualitative screening of citric acid-producing ability of this fungal strain was also performed by using the Czapek-Dox agar medium containing Bromocresol green. Dried and finely powdered Pomegranate peel was used as a principal substrate for the production of citric acid by submerged fermentation. Classical method of citric acid recovery involved a precipitation technique using calcium hydroxide followed by filtration and subsequent treatment with sulphuric acid. The citric acid produced was also chemically detected and titrimetrically estimated by 0.1 N NaOH. Results: The present experiment demonstrated that pomegranate peels may serve as an inexpensive medium for the production of citric acid with a yield of 19.39 g/l by using Aspergillus niger. Conclusion: This study provided an alternative basis to recycle the fruit peel waste of pomegranate in order to achieve industrially feasible and environmentally sustainable bio-production of pharmaceutically significant citric acid

Exploring a Hypothetical Giga-Library of Synthesizable Macrocyclic Composites for the Identification of New Ligands for Protein Surfaces

Many actively pursued pharmacological targets are difficult to drug using conventional small molecule therapeutics because they lack conventional binding sites. These so called ‘undruggable’ targets typically interact with other proteins via shallow, solvent exposed interfaces. Peptidomimetic macrocycles have the potential to mediate such systems because the embedded peptide can mimic native protein structure and recognition elements, and the ring structures contribute to structural preorganization, lowering entropic penalties upon target binding. Compounds of this type having precise shapes and drug-like character are coveted, but are relatively difficult to synthesize. Our lab has developed methods to synthesize shape-defined macrocycles from small linear peptides. These experiments run as processes, wherein designed templates react incrementally with unprotected oligomers to form composite products. The resulting compounds retain molecular recognition elements in the oligomer, yet display that functionality as part of stable polycyclic structures. Our experimental work is based on proteinogenic amino acids and the reactivity of their nucleophilic side chains. However, using unnatural amino acids, the hypothetical scope of the chemistry becomes vast and far outpaces the capacity of our experimental format. Here, we describe the development of a computational rendering of our experimental platform, Composite Peptide Macrocycle Generator (CPMG). This open-source platform simulates our multi-step reaction chemistry using a large, tailored monomer set. We have used the algorithms to anticipate product outcomes of >2 billion processing sequences. We have further developed software to generate three- dimensional structures for each product. Every library member has feature constraints meant to increase the probability of it being bioavailable. We discuss efforts to merge our experimental and computational abilities into a single, iterative workflow to discover new macrocyclic ligands for challenging protein targets. We describe new computational tools and techniques to allow rapid, flexible docking of conformationally dynamic ligands onto multiple protein targets. We describe experiments to validate predictions by synthesizing novel arene amino acids and engaging them in macrocyclizations to generate previously unknown ring systems. We show how the interplay between calculations and synthesis can offer insight into molecular properties and applications

Unprecedented Alkene Transposition in Phthalate-Amino Acid Adducts

A detailed account on the outcome of the thermal reaction between benzylidene phthalides and various amino acid derivatives is reported. It was discovered that the tricyclic pyrroles as previously described are not the products formed in these reactions. Instead under high-temperature conditions decarboxylated phthalamide adducts are formed within 5-10 minutes. Additionally, an unprecedented alkene transposition mechanism has been identified leading to the final products of these reactions.Royal SocietySchool of Chemistry, University College Dublin2020-10-06 JG: PDF replaced with correct versio

Computational generation of an annotated gigalibrary of synthesizable, composite peptidic macrocycles

Peptidomimetic macrocycles have the potential to regulate challenging therapeutic targets. Structures of this type having precise shapes and drug-like character are particularly coveted, but are relatively difficult to synthesize. Our laboratory has developed robust methods that integrate small-peptide units into designed scaffolds. These methods create macrocycles and embed condensed heterocycles to diversify outcomes and improve pharmacological properties. The hypothetical scope of the methodology is vast and far outpaces the capacity of our experimental format. We now describe a computational rendering of our methodology that creates an in silico three-dimensional library of composite peptidic macrocycles. Our open-source platform, CPMG (Composite Peptide Macrocycle Generator), has algorithmically generated a library of 2,020,794,198 macrocycles that can result from the multistep reaction sequences we have developed. Structures are generated based on predicted site reactivity and filtered on the basis of physical and three-dimensional properties to identify maximally diverse compounds for prioritization. For conformational analyses, we also introduce ConfBuster++, an RDKit port of the open-source software ConfBuster, which allows facile integration with CPMG and ready parallelization for better scalability. Our approach deeply probes ligand space accessible via our synthetic methodology and provides a resource for large-scale virtual screening

In Search of Small Molecules That Selectively Inhibit MBOAT4.

Ghrelin is a 28-residue peptide hormone produced by stomach P/D1 cells located in oxyntic glands of the fundus mucosa. Post-translational octanoylation of its Ser-3 residue, catalyzed by MBOAT4 (aka ghrelin O-acyl transferase (GOAT)), is essential for the binding of the hormone to its receptor in target tissues. Physiological roles of acyl ghrelin include the regulation of food intake, growth hormone secretion from the pituitary, and inhibition of insulin secretion from the pancreas. Here, we describe a medicinal chemistry campaign that led to the identification of small lipopeptidomimetics that inhibit GOAT in vitro. These molecules compete directly for substrate binding. We further describe the synthesis of heterocyclic inhibitors that compete at the acyl coenzyme A binding site

In Search of Small Molecules That Selectively Inhibit MBOAT4

Ghrelin is a 28-residue peptide hormone produced by stomach P/D1 cells located in oxyntic glands of the fundus mucosa. Post-translational octanoylation of its Ser-3 residue, catalyzed by MBOAT4 (aka ghrelin O-acyl transferase (GOAT)), is essential for the binding of the hormone to its receptor in target tissues. Physiological roles of acyl ghrelin include the regulation of food intake, growth hormone secretion from the pituitary, and inhibition of insulin secretion from the pancreas. Here, we describe a medicinal chemistry campaign that led to the identification of small lipopeptidomimetics that inhibit GOAT in vitro. These molecules compete directly for substrate binding. We further describe the synthesis of heterocyclic inhibitors that compete at the acyl coenzyme A binding site

Convergent synthesis of thiodiazole dioxides from simple ketones and amines through an unusual nitrogen-migration mechanism

We report the modular preparation of dihydro-1,2,5-thiodiazole dioxide heterocycles starting from methyl ketones and primary amines. This one-pot, three-component coupling employs 2,3-dimethylimidazole-1-sulfonyl azide triflate as a coupling reagent and oxidant. The transformation is scalable and various ketones and amines can be used, yielding thiodiazole dioxide products in up to 89% yield. In addition, 15N- and 13C-labeling studies suggest a mechanism involving a 1,2-nitrogen migration. Together with the mechanistic studies, DFT calculations provide insight into the reaction pathway and set the stage for further exploration of the mechanistic nuances of reactions that use sulfamoyl azides. In combination with the demonstrated modularity of the approach reported herein, the derivatization of the thiodiazole dioxide products highlights the potential of this methodology to rapidly access diverse chemical structures