Screening and characterization of medicinal plants extracts with bactericidal activity against Streptococcus mutans

Abstract

The aim of the present study was to perform a screening of extracts obtained from 15 medicinal plants using water (at 25 and 90?°C) or ethanol (at 25?°C), to bactericidal activity against cariogenic S. mutans ATCC 25175, as well as to carry out the preliminary phytochemical characterization of the extracts and HPLC/MS assay for selected extracts. The extractions were carried out for 5?h at 400?rpm. Only five from 45 tested extracts were selected based on their antibacterial activity. The IC₅₀ varied from of 28?ppm for Quercus ilex up to 250?ppm for Jatropha dioica. Different polyphenolic and quinic acids, flavonoids, anthocyanin or tyrosol were identified by HPLC/MS in selected extracts from Rosa gallica L., Jatropha dioica Sessé, Mimosa tenuiflora (Willd.) Poir, Quercus ilex L., and Solanum nigrum. The obtained results confirm that selected extracts are good candidates to be used for cariogenic bacteria control.     

Water Purification and Microplastics Removal Using Magnetic Polyoxometalate‐Supported Ionic Liquid Phases (magPOM‐SILPs)

Filtration is an established water‐purification technology. However, due to low flow rates, the filtration of large volumes of water is often not practical. Herein, we report an alternative purification approach in which a magnetic nanoparticle composite is used to remove organic, inorganic, microbial, and microplastics pollutants from water. The composite is based on a polyoxometalate ionic liquid (POM‐IL) adsorbed onto magnetic microporous core–shell Fe₂O₃/SiO₂ particles, giving a magnetic POM‐supported ionic liquid phase (magPOM‐SILP). Efficient, often quantitative removal of several typical surface water pollutants is reported together with facile removal of the particles using a permanent magnet. Tuning of the composite components could lead to new materials for centralized and decentralized water purification systems.     

Molecular complexity and the control of self-organising processes

In this article we investigate the complexity of the molecular architectures of liquid crystals based on rod-like mesogens. Starting from simple monomeric systems founded on fluoroterphenyls, we first examine the effects of aromatic core structure on mesophase formation from the viewpoint of allowable polar interactions, and then we model these interactions as a function of terminal aliphatic chain length. By incorporating a functional group at the end of one, or both, of the aliphatic chains we study the effects caused by intermolecular interfacial interactions in lamellar phases, and in particular the formation of synclinic or anticlinic modifications. We then develop these ideas with respect to dimers, trimers, tetramers, etc. We show, for dendritic systems, that at a certain level of molecular complexity the local mesogenic interactions become irrelevant, and it is gross molecular shape that determines mesophase stability. The outcome of these studies is to link the complexity of the molecular interactions at the nanoscale level, which lead to the creation of the various liquid-crystalline polymorphs, with the formation of mesophases that are dependent on complex shape dependencies for mesoscopic supermolecular architectures.     

Influence of matrix on suitability of four methods for organochlorine pesticide analysis in waters

The monitoring of organochlorine pesticides has raised a great concern in the last years due to their toxicity (some of them are carcinogenic and endocrine disruptor compounds) and persistence. European Directive 2008/105/EC establishes very restrictive levels for organochlorine pesticides in surface waters. Therefore, simple, fast, highly sensitive and low cost analytical methods are required to detect and quantify these pollutants in water. In the present work, four procedures for extraction and determination are proposed and compared for the analysis of 28 organochlorine pesticides in tap, surface and sea waters. The suitability of each method of analysis was evaluated for each kind of water. The extraction methods proposed were: two solid-phase extraction methods using C₁₈ laminar disk and Oasis HLB cartridges, a solid-phase microextraction procedure using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, and a micro liquid–liquid extraction procedure using ethyl acetate as solvent. Determination of pesticides was performed by large volume on-column injector-gas chromatography-electron capture detection (LVOCI-GC-ECD), splitless-GC-ECD and GC-MS (mass spectrometry). All methods present a good sensitivity with method detection limits lower than 10?ng?L^?1, good accuracy with recoveries between 75 and 120% (with some exceptions) and good precision (relative standard deviations <15%), according to the Commission Decision 2002/657/EC criteria. The advantages and disadvantages of each method are discussed in terms of the green chemistry principles, the figures of merit and the matrix effect. This work tries to be a useful guidance for routine and control analysis laboratories.     

Determination of microcystins in biological samples from freshwater fish

A new HPLC–DAD method has been developed to identify and quantify free microcystins (MC) in biological samples from fish (intestine and liver). The toxins were extracted from 500 mg sample with a mixture of methanol–water (85 : 15, v/v) and the extracts obtained were purified employing immunoaffinity columns (IAC). The purification step was optimised by a full factorial 3² design. MC were separated using conventional C18 column and an acetonitrile-acidified water (pH 3) gradient. Detection and quantification limits resulted equal for the two toxins assayed (MC-RR and MC-LR) and were 0.15 and 0.5 µg g^?1, respectively. The accuracy for each MC in liver samples were 96% (range 80–113%) for MC-RR and 101% (range 93–118%) for MC-LR. The results were slightly lower for intestine samples, with recoveries ranging between 85% (75–93%) for MC-RR and 88% (80–97%) for MC-LR. The proposed method was applied for the determination of free MC in fish intoxicated with these toxins, in order to determine its utility to evaluate the potential risks for human health if MC-contaminated fish are consumed. The results showed the transference of MC-LR from cyanobacterial cells to fish tissues.     

Biological study and electrochemical characterization of Cu(II) and 1,8-bis-(2-pyridyl)-3,6-dithiaoctane (pdto) complex

Preliminary proliferation assays in human tumor cervix line HeLa, using the coordination compound [Cu(pdto)H₂O]²⁺ (pdto = 1,8-bis-(2-pyridyl)-3,6-dithiaoctane) and its precursors Cu(NO₃)₂ · 2.5H₂O and pdto, were carried out. The results showed that the copper complex has a behavior similar to that of the reference drug cis-platin. No biological activity for the non-coordinated ligand and the copper salt was found. It was established by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy, that the complex [Cu(pdto)H₂O]²⁺ presents an electrochemical reversible Cu(II)/Cu(I) reduction, in acetonitrile solution, meanwhile, the copper salt Cu(NO₃)₂ · 2.5H₂O exhibited an electrochemical irreversible behavior. A comparison between biological and electrochemical results corresponding to [Cu(pdto)H₂O]²⁺ and Cu(NO₃)₂ · 2.5H₂O let us to proposed, the electrochemical reversibility, as one important factor in the antitumoral activity of the copper complex. Due to the nature of the studies presented in this work, other factors like intercalation properties with DNA cannot be neglected in the antitumoral activity of the complex.     

Mo4(η3‐allyl)4Cl2(OH)2(CO)8: the first cubane‐type Mo2+ organometallic complex with μ3‐OH and μ3‐Cl bridges

The reaction between fluorenyllithium and Mo(η³‐C₃H₅)Cl(NCMe)₂(CO)₂ led to the isolation of di‐μ₃‐chlorido‐di‐μ₃‐hydroxido‐tetrakis[(η³‐allyl)dicarbonylmolybdenum(II)]–9‐fluorenone–tetrahydrofuran (1/1/1), [Mo₄(C₃H₅)₄Cl₂(OH)₂(CO)₈]·C₄H₈O·C₁₃H₈O. The tetrametallic Mo₄ unit constitutes the first example of a complex containing simultaneously two μ₃‐OH groups and two μ₃‐Cl anions capping the metallic trigonal prism. The four crystallographically independent Mo²⁺ centres exhibit distorted octahedral geometry with the η³‐allyl groups being trans‐coordinated to a μ₃‐OH group and the carbonyl groups occupying the equatorial plane. Space‐filling tetrahydrofuran and 9‐fluorenone molecules are engaged in strong O—H...O hydrogen‐bonding interactions with Mo₄(η³‐allyl)₄Cl₂(OH)₂(CO)₈ complexes.     

An optimization model for the design of a capacitated multi-product reverse logistics network with uncertainty

In this work the design of a reverse distribution network is studied. Most of the proposed models on the subject are case based and, for that reason, they lack generality. In this paper we try to overcome this limitation and a generalized model is proposed. It contemplates the design of a generic reverse logistics network where capacity limits, multi-product management and uncertainty on product demands and returns are considered. A mixed integer formulation is developed which is solved using standard B&B techniques. The model is applied to an illustrative case.     

Spectroscopic analysis of imidazolidines. Part I: Electron impact mass spectrometry

The electron impact mass spectral fragmentation pathways for a series of 1,3‐di‐ and 1,2,3‐trisubstituted imidazolidines were investigated. The data show remarkable differences depending on the location and identity of substituents. The atypical 1,2,2,3‐tetrasubstituted imidazolidine, 2‐cyano‐1‐methyl‐3‐(p‐nitro‐phenyl)‐2‐phenylimidazolidine, was also investigated.