Mario Salazar - Academia.edu (original) (raw)

Papers by Mario Salazar

Natural products and bioprospecting, Jun 1, 2024

The generation of chemically engineered essential oils (CEEOs) prepared from bi-heteroatomic reac... more The generation of chemically engineered essential oils (CEEOs) prepared from bi-heteroatomic reactions using ammonium thiocyanate as a source of bioactive compounds is described. The impact of the reaction on the chemical composition of the mixtures was qualitatively demonstrated through GC-MS, utilizing univariate and multivariate analysis. The reaction transformed most of the components in the natural mixtures, thereby expanding the chemical diversity of the mixtures. Changes in inhibition properties between natural and CEEOs were demonstrated through acetylcholinesterase TLC autography, resulting in a threefold increase in the number of positive events due to the modification process. The chemically engineered Origanum vulgare L. essential oil was subjected to bioguided fractionation, leading to the discovery of four new active compounds with similar or higher potency than eserine against the enzyme. The results suggest that the directed chemical transformation of essential oils can be a valuable strategy for discovering new acetylcholinesterase (AChE) inhibitors.

ACS Combinatorial Science, Dec 17, 2010

The chemical composition and the biomolecular properties of a crude plant extract were altered th... more The chemical composition and the biomolecular properties of a crude plant extract were altered through bromination leading to the discovery of an acetylcholinesterase inhibitor.

ACS Combinatorial Science, May 13, 2016

The generation of fluorinated essential oils as a source of bioactive compounds is described. Mos... more The generation of fluorinated essential oils as a source of bioactive compounds is described. Most of the components of the natural mixtures were altered, leading to the discovery of a new fluorinated tyrosinase inhibitor.

N a-benzenesulfonylhistamine, a new semi-synthetic b-glucosidase inhibitor, was obtained by bioac... more N a-benzenesulfonylhistamine, a new semi-synthetic b-glucosidase inhibitor, was obtained by bioactivityguided isolation from a chemically engineered extract of Urtica urens L. prepared by reaction with benzenesulfonyl chloride. In order to identify better b-glucosidase inhibitors, a new series of N a ,N s-diarylsulfonyl and N a-arylsulfonyl histamine derivatives was prepared. Biological studies revealed that the b-glucosidase inhibition was in a micromolar range for several N a-arylsulfonyl histamine compounds of the series, N a-4-fluorobenzenesulfonyl histamine being the most powerful compound. Besides, this reversible and competitive inhibitor presented a good selectivity for b-glucosidase with respect to other target enzymes including a-glucosidase.

Phytochemical Analysis, Jun 23, 2015

Introduction-The prevailing treatment for Alzheimer's disease is the use of acetylcholinesterase ... more Introduction-The prevailing treatment for Alzheimer's disease is the use of acetylcholinesterase (AChE) inhibitors. Natural extracts are the principal source of AChE's inhibitors. However, their chemical complexity demands for simple, selective and rapid assays. Objective-To develop a strategy for identification of AChE inhibitors present in mixtures employing high resolution mass spectrometry (HRMS) and thin layer chromatography (TLC)-biological staining. Methodology-The strategy uses an autographic assay based on the α-naphthyl acetatefast blue B system for the detection of AChE activity. The immobilisation of AChE in agar allowed the extraction of the compounds for analysis by HRMS. Three TLC experiments employing different solvent systems were used in parallel and the mass spectra of the compounds extracted from the inhibition halos, were compared. The analysis was performed under MatLab environment. Results-The strategy was used to detect the presence of physostigmine in an extract of Brassica rapa L. spiked with the inhibitor. Similarly, caffeine was straightforwardly spotted as responsible for the inhibitory properties of an extract of Ilex paraguariensis Saint-Hilaire. Comparison of the HRMS profiles lead to the facile identification of the [M+H] + and [M+Na] + of the compounds responsible for the inhibition. Conclusion-The proposed methodology, coupling TLC-AChE autography-HRMS, illustrates the feasibility of assigning molecular formulas of active compounds present in complex mixtures directly from autography. The new AChE agar-immobilised assay presented a more homogenous colour and a better definition than direct spraying methods, reducing the cost of the assay and improving its sensitivity.

Accounts of Chemical Research, Feb 28, 2011

B iological research and drug discovery critically depend on access to libraries of small molecul... more B iological research and drug discovery critically depend on access to libraries of small molecules that have an affinity for biomacromolecules. By virtue of their sustained success as sources of lead compounds, natural products are recognized as "privileged" starting points in structural space for library development. Compared with synthetic compounds, natural products have distinguishing structural properties; indeed, researchers have begun to quantify and catalog the differences between the two classes of molecules. Measurable differences in the number of chiral centers, the degree of saturation, the presence of aromatic rings, and the number of the various heteroatoms are among the chief distinctions between natural and synthetic compounds. Natural products also include a significant proportion of recurring molecular scaffolds that are not present in currently marketed drugs: the bioactivity of these natural substructures has been refined over the long process of evolution. In this Account, we present our research aimed at preparing libraries of semisynthetic compounds, or chemically engineered extracts (CEEs), through chemical diversification of natural products mixtures. The approach relies on the power of numbers, that is, in the chemical alteration of a sizable fraction of the starting complex mixture. Major changes in composition can be achieved through the chemical transformation of reactive molecular fragments that are found in most natural products. If such fragments are common enough, their transformation represents an entry point for chemically altering a high proportion of the components of crude natural extracts. We have searched for common reactive fragments in the Dictionary of Natural Products (CRC Press) and identified several functional groups that are expected to be present in a large fraction of the components of an average natural crude extract. To date, we have used reactions that incorporate (i) nitrogen atoms through carbonyl groups, (ii) sulfur by transformation of-OH and amines, and (iii) bromine through double bonds and aromatic rings. The resulting CEEs had different composition and biomolecular properties than their natural progenitors. We isolated a semisynthetic β-glucosidase inhibitor from a CEE prepared by reaction with benzenesulfonyl chloride, an antifungal pyrazole from a CEE prepared by reaction with hydrazine, and an acetylcholinesterase inhibitor from a CEE prepared through bromination. Our results illustrate how biological activity can be generated through chemical diversification of natural product mixtures. Moreover, the level of control that can be asserted in the process by judicious design and experimental choices underscores the potential for further development of CEEs in both basic research and drug discovery.

Food Chemistry, Oct 1, 2022

Microchemical Journal, Sep 1, 2018

Argentine citrus industry stands out among the top ten largest producers of citrus of the world. ... more Argentine citrus industry stands out among the top ten largest producers of citrus of the world. Traceability is a key point of the quality control in the international trade context. Discrimination between orange juices produced from different geographical regions in Argentina (San Pedro and Entre Ríos), has been achieved by applying principal components analysis (PCA) and partial least-squaresdiscriminant analysis (PLS-DA) to 1 H NMR spectra of the juices. Different regions of the spectra were analyzed in view of the large range of signal intensities and the chemometric treatment of the NMR data has successfully distinguished the juice of different origins/varieties, as well as the metabolites responsible for their separation. Examination of the PCA loadings showed that citric acid and ethanol levels were the main chemical variables for sample discrimination.

RSC Advances, 2018

RSC Advances, 2016

A set of chemically engineered essential oils has been generated through chemical diversification... more A set of chemically engineered essential oils has been generated through chemical diversification by reaction with bromine, leading to the discovery of a new brominated xanthine oxidase inhibitor.

Bioorganic & Medicinal Chemistry Letters, Sep 1, 2009

The chemical composition and the biomolecular properties of a series of crude plant extracts were... more The chemical composition and the biomolecular properties of a series of crude plant extracts were altered without previous knowledge of their detailed chemical composition.

Studies in natural products chemistry, 2019

Abstract Natural products are recognized as privileged starting points in the structural space fo... more Abstract Natural products are recognized as privileged starting points in the structural space for library development by virtue of their sustained success as sources of lead compounds. Natural products have more distinct structural properties than synthetic compounds. They differ in the number of chiral centers, degree of saturation, presence of aromatic rings, and number of heteroatoms. Natural products also include a significant proportion of recurring molecular scaffolds that have been refined over the long process of evolution. This review chapter discusses research aimed at preparing chemically engineered extracts (CEEs) by chemically diversifying natural product mixtures. The approach relies on the power of numbers (i.e., chemical alteration of a sizable fraction of the starting complex mixture). Major changes in composition can be achieved by chemical transformation of reactive molecular fragments that are found in most natural products. If such fragments are common enough, their transformation represents an entry point to chemically alter a high proportion of the components of crude natural extracts. To date, different reactions have been used to incorporate nitrogen, sulfur, bromine, fluorine, etc. The resulting CEEs had different compositions and biomolecular properties than their natural progenitors and have been the sources for semisynthetic bioactive compounds such as a β-glucosidase inhibitor from a CEE prepared by reaction with benzenesulfonyl chloride, antifungal or antiamyloidogenic pyrazoles from a CEE prepared by reaction with hydrazine, an acetylcholinesterase inhibitor, a xanthine oxidase inhibitor from CEEs prepared through bromination, and a tyrosinase inhibitor from a CEE prepared by fluorination. These examples illustrate how biological activity can be generated by chemically diversifying natural product mixtures.

RSC medicinal chemistry, 2020

A series of simple N-arylbenzenesulfonyl histamine derivatives were prepared and screened against... more A series of simple N-arylbenzenesulfonyl histamine derivatives were prepared and screened against α-glucosidase. Inhibition was in the micromolar range for several Nα,Nτ-di-arylsulfonyl compounds, with Nα,Nτ-di-4-trifluorobenzenesulfonyl histamine (IId) being the best inhibitor. Compound IId is a reversible and competitive α-glucosidase inhibitor, and presented good selectivity with respect to other target enzymes, including β-glucosidase and α-amylase, and interesting predicted physicochemical properties. Docking studies have been run to postulate ligand–enzyme interactions to account for the experimental results. In vivo, compound IId produced a similar hypoglycemic effect to acarbose with half of its dose.

European Journal of Organic Chemistry

Concomitant selective dehydroxylation during the transformation of flavones into pyrazoles with h... more Concomitant selective dehydroxylation during the transformation of flavones into pyrazoles with hydrazine is determined by the A‐ring substitution pattern and propensity to keto enol tautomerization. The obtained pyrazoles show varied tyrosinase inhibition properties, including one nanomolar inhibitor.

Methods in Molecular Biology

Enzymatic bioautography enables the detection of enzyme inhibitors absorbed on a thin-layer chrom... more Enzymatic bioautography enables the detection of enzyme inhibitors absorbed on a thin-layer chromatography plate. Therefore, it is an assay format that is particularly useful for the detection of inhibitors present in complex mixtures. The inhibition properties of compounds separated by thin-layer chromatography can be directly analyzed to produce an inhibition profile. Here, we describe the conditions to detect inhibitor of the enzymes xanthine oxidase and β-glucosidase immobilized on agar gel.

Industrial Crops and Products, 2020

Abstract Chemical transformation of plant extracts can lead to the generation of semisynthetic de... more Abstract Chemical transformation of plant extracts can lead to the generation of semisynthetic derivatives that display biomolecular properties that were absent in the natural components of the starting material. The objective of this work was to produce new α-glucosidase inhibitors through O-sulfonylation of essential oils. Thirteen essential oils were chemically diversified with benzenesulfonyl chloride and screened for their in vitro α-glucosidase inhibitory effect. The chemically engineered Origanum vulgare L. (Lamiaceae) essential oil showed the highest inhibition percentage of the series. Using chromatography, nuclear magnetic resonance, and mass spectrometry, the benzenesulfonyl esters of thymol and carvacrol were identified as responsible compounds for the observed α-glucosidase inhibition. Therefore, a series of twelve arylsulfonyl esters of carvacrol and thymol was prepared. These compounds showed interesting physicochemical properties in silico. Their α-glucosidase inhibition evaluation revealed three compounds with half maximal inhibitory concentration values in the low micromolar range (≅ 2.5 μM), i.e., fifty times more active than acarbose. These compounds showed good selectivity for α-glucosidase compared with α-amylase, β-glucosidase, and β-galactosidase. The two most potent compounds, 7 and 8, are reversible and mixed type α-glucosidase inhibitors. The results indicate that the directed chemical transformation of essential oils can be a useful strategy to discover new α-glucosidase inhibitors.

ACS Combinatorial Science, 2019

The enzyme tyrosinase is involved in the biosynthesis of melanin and the enzymatic browning of fr... more The enzyme tyrosinase is involved in the biosynthesis of melanin and the enzymatic browning of fruits and vegetables, so its inhibitors have potential as agents to treat hyperpigmentary disorders or as food anti-browning agents. The use of hydrazine monohydrate as reagent to prepare chemically engineered extracts can lead to semisynthetic compounds that contain the portion N-N, a fragment rarely found in natural products and present in some tyrosinase inhibitors. Here, we report the tyrosinase inhibition screening of a series of chemically engineered extracts diversified by reaction with hydrazine. LC-MS was used to evaluate the change in composition produced by the reaction. Bioguided fractionation of the most active chemically engineered extract, prepared from Matricaria recutita L., led to the discovery of a pyrazole that inhibits tyrosinase with an IC 50 value of 28.20  1.13 µM. This compound was produced by a one-pot double chemical transformation, of its natural precursor, that includes an unexpected selective removal of one-OH group.

Phytochemical Analysis, 2007

A new bioautographic assay suitable for the localisation of beta-glucosidase inhibitors present i... more A new bioautographic assay suitable for the localisation of beta-glucosidase inhibitors present in a complex matrix is described. Enzyme activity was detected using esculin as the substrate to produce esculetin, which reacts with ferric ion to form a brown complex.

Journal of Biological Chemistry, 2013

Background: The PhoP/PhoQ system governs crucial Salmonella typhimurium pathogenic traits. Result... more Background: The PhoP/PhoQ system governs crucial Salmonella typhimurium pathogenic traits. Results: A screening of natural compounds showed that long chain fatty acids present in the bacterial growth medium downregulate the PhoP/PhoQ-dependent regulon. Conclusion: Long chain unsaturated fatty acids specifically inhibit PhoQ autokinase activity. Significance: The novel PhoQ input signal reveals a new scenario for the control of Salmonella virulence, providing a rationale for future antibacterial strategies.

Bioorganic & Medicinal Chemistry Letters, 2009