Contact Ion Pairs on a Protonated Azamacrocycle: the Role of the Anion Basicity

A potassium-containing hexaazamacrocyclic dication, [M•H•K]2+, is able to add in the gas phase mono- and dicarboxylate anions as well as inorganic anions by forming the corresponding monocharged adducts, the structure of which markedly depends on the basicity of the anion. With anions, such as acetate or fluoride, the neutral hexaazamacrocycle M acts as an acceptor of monosolvated K+ ion. With less basic anions, such as trifluoroacetate or chloride, the protonated hexaazamacrocycle [M•H]+ performs the unusual functions of an acceptor of contact K+/anion pairs

Chemical Composition and Anti-Candida Activity of Mentha suaveolens Ehrh. Essential Oils Obtained by Different Distillation Processes

A comparative study on essential oils extracted from Mentha suaveolens Ehrh. from Italy is reported. Two extraction procedures were investigated: hydrodistillation and steam distillation, carried out as a continuous and fractionated procedure. Fresh and dried plant material from two harvests was used. The hydrodistillation method yielded a higher amount of essential oil. The dried plant was significantly richer in essential oil per kg of starting plant material. Gas chromatography-mass spectrometry analysis of 112 samples showed that the essential oils belong to the piperitenone oxide-rich chemotype. In addition, piperitenone, p-cymen-8-ol, and limonene were among the most abundant compounds in the different samples. A higher amount of piperitenone oxide was obtained by hydrodistillation, while steam distillation gave a higher percentage of piperitenone and limonene. The essential oils were characterized for their anti-Candida albicans activity; higher potency was observed for the samples rich in piperitenone oxide, with MIC values ranging from 0.39 to 0.78 mg·mL−1 (0.039% and 0.078% p/v). The results of this work provide a deep insight into the methodology of essential oil extraction and the associated chemical variability of M. suaveolens Ehrh. Some of the essential oils are potent against C. albicans and could be considered for potential use in therapy

Effect of different soil treatments on production and chemical composition of essential oils extracted from Foeniculum vulgare Mill., Origanum vulgare L. and Thymus vulgaris L

The aim of the present study was to investigate how essential oil production and associated chemical composition and related biological activity could be influenced by different cultivation treatments and distillation method. Foeniculum vulgare Mill. (fennel), Origanum vulgare L. (oregano), and Thymus vulgaris L. (thyme) were cultivated in absence of any fertilizer (control) and in presence of three different fertilizers: a chemical one with augmented of mineral phosphorus and potassium, a second added with hydrolysed organic substance and mineral phosphorus and potassium (organic-mineral) and a third one treated with high content of organic nitrogen of protein origin (organic). The plants were subjected to steam distillation using two modalities: recycled and continuous to obtain 32 essential oil samples. Chemical composition analysis was performed by gas chromatography-mass spectrometry; in vitro antimicrobial activity was evaluated by broth microdilution method. In general, the recycled distillation method appeared to have a slightly higher yield than the continuous method. The "mineral" and "organic-mineral" treatments resulted in the higher yield compared to the "organic" or "control" treatments, and this was particularly evident in the recycled method. The "control" plants had a lower yield of essential oils. Anethole (13.9-59.5%) and estragole (13.4-52.2%) were the main constituents of fennel oils, p-cymene and its derivatives carvacrol and thymol were the main constituents of oregano and thyme samples. The antimicrobial activity of thyme oils on Staphylococcus aureus ranged from 0.31 to 0.16% (v/v); a lower effect of oregano samples and no activity of fennel samples were observed. The essential oils failed to inhibit the growth of Pseudomonas aeruginosa strains

Chemico-biological characterization of Torpedino Di Fondi® tomato fruits. A comparison with San Marzano cultivar at two ripeness stages

Torpedino di Fondi (TF) is a hybrid tomato landrace developed in Sicily and recently introduced in the south Lazio area along with the classical San Marzano (SM) cultivar. The present study aimed at characterizing TF tomatoes at both pink and red ripening stages, and at comparing them with traditional SM tomatoes. A multidisciplinary approach consisting of morphological, chemical (FT‐ICR MS, NMR, HPLC, and spectrophotometric methods), and biological (antioxidant and antifungal in vitro activity) analyses was applied. Morphological analysis confirmed the mini‐ San Marzano nature and the peculiar crunchy and solid consistency of TF fruits. Pink TF tomatoes displayed the highest content of hydrophilic antioxidants, like total polyphenols (0.192 mg/g), tannins (0.013 mg/g), flavonoids (0.204 mg/g), and chlorophylls a (0.344 mg/g) and b (0.161 mg/g), whereas red TF fruits were characterized by the highest levels of fructose (3000 mg/100 g), glucose (2000 mg/100 g), tryptophan (2.7 mg/100 g), phenylalanine (13 mg/100 g), alanine (25 mg/100 g), and total tri‐unsaturated fatty acids (13% mol). Red SM fruits revealed the greatest content of lipophilic antioxidants, with 1234 mg/g of total carotenoids. In agreement with phenolics content, TF cultivar showed the greatest antioxidant activity. Lastly, red TF inhibited Candida species (albicans, glabrata and krusei) growth

Top predator status and trends: ecological implications, monitoring and mitigation strategies to promote ecosystem-based management

The conservation and management of marine ecosystems hinge on a comprehensive understanding of the status and trends of top predators. This review delves into the ecological significance of marine top predators, examining their roles in maintaining ecosystem stability and functioning through an integrated analysis of current scientific literature. We first assess the efficacy of various monitoring methods, ranging from traditional field observations to cutting-edge technologies like satellite tracking and environmental DNA (eDNA) analysis and evaluating their strengths and limitations in terms of accuracy, spatial coverage, and cost-effectiveness, providing resource managers with essential insights for informed decision-making. Then, by synthesizing data from diverse marine ecosystems, this study offers a comprehensive overview of the trends affecting top predator populations worldwide. We explore the multifaceted impacts of human activities, climate change, and habitat degradation on the abundance and distribution of these key species. In doing so, we shed light on the broader implications of declining top predator populations, such as trophic cascades and altered community structures. Following a thorough assessment of successful strategies for reversing the decline of top predators, a compilation of recommendations is presented, encompassing effective governance interventions. A crucial aspect of effective ecosystem-based management is the implementation of robust monitoring strategies. Mitigation measures are imperative to reverse the adverse impacts on marine top predators. We present a comprehensive array of mitigation options based on successful case studies. These include the establishment of marine protected areas, the enforcement of fisheries regulations, and the promotion of sustainable fishing practices. We deepen the synergies between these strategies and their potential to mitigate human-induced stressors on top predator populations to safeguard their pivotal role in maintaining marine ecosystem structure and function. By examining marine top predators’ ecological significance, analyzing population trends, discussing monitoring techniques, and outlining effective mitigation strategies, we provide a comprehensive resource for researchers, policymakers, and stakeholders engaged in fostering ecosystem-based management approaches. We conclude that integrating these insights into current management frameworks will be essential to safeguard both top predators and the broader marine environment for future generations

Enantioselective supramolecular devices in the gas phase

Resorcin[4]arenes represents a class of widely studied macrocycles with remarkable complexing properties towards inorganic and organic compounds. In 2007 Zhang et al. indicated them as the third best host molecules, right after cyclodextrin and crown ethers. Their success in the host-guest chemistry is principally due to the tunability of their synthesis. In principle the lower rim’s chains of resorcin[4]arenes can be functionalized with a large number of chemical groups, which strictly influences the conformational space available to the structure. Furthermore the conformation of the macrocycle defines its coordinating capabilities as well as its selectivity. Such a versatility can include the possibility to employ even a supramolecular chirality which can be obtained in two ways: 1) the presence of stereogenic centres in the lateral chains; 2) the hindered spatial arrangement of achiral subunits forming a chiral macrocyclic scaffold. In the last decade the application of resorcin[4]arenes in different analytical and biochemical fields has been continuously growing: i) chromatography, as stationary phase as well as component of liquid phases;(1,2) ii) NMR, as solvating agent;(3) iii) pharmacology, as biocompatible drug carrier.(4) These applications are usually carried out in liquid media, where the host-guest interactions result from the superimposition of the intrinsic effect of the non-covalent supramolecular interactions and the solvation effect.Here we present a comprehensive gas phase study of the molecular recognition of several chiral resorcin[4]arenes towards different enantiopure compounds (i.e. amino acids and their derivatives, nucleosides, alkaloids).(5-9) The isolated state allows us to exclude the solvation effects and to purely investigate the intimate nature of the host-guest interactions. The gaseous adducts have been studied by means of different mass spectrometry approaches which provided us multifaceted information on the structure (IRMPD), thermodynamics (ESI-CID), and reactivity (ESI-FT-ICR) of resorcin[4]arenes based adducts, in order to shed light on the effect which supramolecular chirality exerts on chemico-physical properties of these host-guest complexes. Information of this kind provide the organic chemists a positive feedback to stimulate or even inspire the synthesis of new macrocycles applicable to different chemical fields

Does a Chiral Alcohol Really Racemize when Its OH Group Is Protected with Boyer's Reaction?

Chiral reactants have been employed for assessing the real stereochemistry of the BiBr(3)-catalyzed synthesis of benzylic ethers, a very useful reaction for protecting alcoholic groups. The results of this investigation are in clear contrast with the conclusions of previous studies (Boyer et al., Tetrahedron 2001;57:1917-1921). Indeed, chiral GC-MS analysis of the ethereal products gives unequivocal evidence of the complete racemization of the benzylic moiety and the complete retention of configuration of the protected alcoholic substrate. Such findings make BiBr(3) a powerful and stereo-chemically preservative catalyst for benzylation of chiral alcohols, and a potential candidate for orthogonal protecting group strategies applicable to polyhydroxy compounds. Chirality 22:88-91, 2010. (C) 2009 Wiley-liss, Inc

Reaction diastereoselectivity of chiral aminoalcohols/[Co(II)NO3]+ complexes in evaporating ESI nanodroplets: new insights from a joint experimental and computational investigation.

The nature of the ionic species, formed by electrospray ionization (ESI) of Co(NO3)2/CH3OH solns. with a pair of aminoalcs. W and Y, has been investigated by mass spectrometric and computational methods. Collision induced dissocn. (CID) of ions, formally corresponding to the [WYCoNO3]+ structures, yields fragmentation patterns which reflect not only the expected [WYCoNO3]+ connectivity but also that of other isomeric structures. Formation of these latter species is obsd. only in the presence of a tertiary aminoalc., like N-methylpseudoephedrine. The CID patterns are found to be strongly dependent on the chem. form (whether the free aminoalc. or its hydrochloride), the configuration, and the relative concn. of the W and Y aminoalcs. This variability parallels the results of classical MD (mol. dynamics) simulations of the [WYCoNO3]+ adducts which show a drastic alteration of the mech.-dynamical features of the adducts by simply changing the charge state of W and/or Y, their abs. configuration, or by removing the solvent. The present exptl. and computational study confirms the observation of fast stereoselective reactions in ESI nanodroplets before their evapn. and warns against any automatic correlation between the ESI spectrum of an analyte and its structure in soln

Intramolecular n-type proton/hydrogen network in basic structures of vitamin B6 investigated by IRMPD spectroscopy

A combined IRMPD and DFT study of the isomeric forms of protonated pyridoxine, pyridoxamine and pyridoxal has allowed to establish the spectroscopic and some peculiar structural features of these basic components of the vitamin B6 group in the gas phase, with the aim to offer a standpoint free from the environmental effects, which could help in understanding their behavior in the condensed phase typical of biological systems. The imine-enamine and the neutral-zwitterion tautomerism have been considered. Analyzing the experimental and theoretical data a detailed characterization of the protonation sites and intramolecular proton/hydrogen bonding interactions emerged. The comparison between experimental and theoretical signals of free N-H and O-H bonds and when they are involved as proton/hydrogen bond donors towards n-acceptors suggests a correspondence between their anharmonicity and the intensity of the IRMPD signals, up to the so called IRMPD transparency. (C) 2019 Elsevier B.V. All rights reserved

Theoretical-computational modeling of gas-state thermodynamics in flexible molecular systems: ionic liquids in the gas phase as a case study

A theoretical-computational procedure based on the quasi-Gaussian entropy (QGE) theory and molecular dynamics (MD) simulations is proposed for the calculation of thermodynamic properties for molecular and supra-molecular species in the gas phase. The peculiarity of the methodology reported in this study is its ability to construct an analytical model of all the most relevant thermodynamic properties, even within a wide temperature range, based on a practically automatic sampling of the entire conformational repertoire of highly flexible systems, thereby bypassing the need for an explicit search for all possible conformers/rotamers deemed relevant. In this respect, the reliability of the presented method mainly depends on the quality of the force field used in the MD simulations and on the ability to discriminate in a physically coherent way between semi-classical and quantum degrees of freedom. The method was tested on six model systems (n-butane, n-butane, n-octanol, octadecane, 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic pairs), which, being experimentally characterized and already addressed by other theoretical-computational methods, were considered as particularly suitable to allow us to evaluate the method's accuracy and efficiency, bringing out advantages and possible drawbacks. The results demonstrate that such a physically coherent yet relatively simple method can represent a further valid computational tool that is alternative and complementary to other extremely efficient computational methods, as it is particularly suited for addressing the thermodynamics of gaseous systems with a high conformational complexity over a large range of temperature