State of the Art on Developments of (Bio)Sensors and Analytical Methods for Rifamycin Antibiotics Determination.

This review summarizes the literature data reported from 2000 up to the present on the development of various electrochemical (voltammetric, amperometric, potentiometric and photoelectrochemical), optical (UV-Vis and IR) and luminescence (chemiluminescence and fluorescence) methods and the corresponding sensors for rifamycin antibiotics analysis. The discussion is focused mainly on the foremost compound of this class of macrocyclic drugs, namely rifampicin (RIF), which is a first-line antituberculosis agent derived from rifampicin SV (RSV). RIF and RSV also have excellent therapeutic action in the treatment of other bacterial infectious diseases. Due to the side-effects (e.g., prevalence of drug-resistant bacteria, hepatotoxicity) of long-term RIF intake, drug monitoring in patients is of real importance in establishing the optimum RIF dose, and therefore, reliable, rapid and simple methods of analysis are required. Based on the studies published on this topic in the last two decades, the sensing principles, some examples of sensors preparation procedures, as well as the performance characteristics (linear range, limits of detection and quantification) of analytical methods for RIF determination, are compared and correlated, critically emphasizing their benefits and limitations. Examples of spectrometric and electrochemical investigations of RIF interaction with biologically important molecules are also presented.

Chemical Composition, Antipathogenic and Cytotoxic Activity of the Essential Oil Extracted from Amorpha fruticosa Fruits.

The purpose of this paper was to characterize and investigate the antimicrobial potential of Amorpha fruticosa fruits essential oil (EO). The EO was extracted by hydrodistillation, analyzed by GC-MS, and then evaluated for its interaction with microbial and mammalian cells. The antimicrobial activity was assessed against bacterial and fungal strains, in a planktonic and adherent growth state, using qualitative and quantitative assays. The main components identified in A. fruticosa fruits EO were δ-cadinene, γ-muurolene, and α-muurolene. The Gram-positive strains proved to be more susceptible than Gram-negative bacteria and fungal strains. The EO exhibited good antibiofilm activity, inhibiting the microbial adherence to the inert (96-well plates and Foley catheter section) and cellular substrata. The flow cytometry analysis revealed as one of the possible mechanisms of antimicrobial action the alteration of cell membrane hydrophobicity. The cytotoxicity on the L929 cell line occurred at concentrations higher than 0.3 mg/mL. Taken together, our results demonstrate that A. fruticosa fruits EO contains active compounds with selective inhibitory effect on different microbial strains in planktonic and biofilm growth state, explained at least partially by the interference with microbial membranes due to their hydrophobic character.

An experimental design for the optimization of the extraction methods of metallic mobile fractions from environmental solid samples.

The evaluation of the cadmium and lead mobile forms from environmental solid samples provides information about their mobility and bioavailability. In the present study, the Cd and Pb mobile fractions were obtained by two modified extraction methods applied to industrial and acidic pH soils or to polluted sediments. In order to highlight that the extraction procedure does not significantly influence the quantitative atomic absorption spectrometric determination of cadmium and lead, the robustness of the extraction methods was evaluated and proven applying a Youden and Steiner factorial design. Within this experimental design, the shaking rate, the shaking time, and the solid/liquid extraction ratio were modified. The measurement uncertainty of the whole analytical procedure was assessed, the contribution of the factors involved in the extraction process being insignificant compared to the other uncertainty sources. The importance of the study is related to the fact that it proves the applicability in the routine laboratory practice of the modified extraction methods by increasing the extraction ratio following thorough optimization and robustness studies.

Voltammetric determination of polyphenolic content as rosmarinic acid equivalent in tea samples using pencil graphite electrodes.

The quasi-reversible, diffusion controlled behavior of rosmarinic acid (RA) on a disposable pencil graphite electrode (PGE) was established by cyclic voltammetry. Using the anodic oxidation peak presented by RA on the PGE a differential pulse voltammetric (DPV) method was developed for the quantitative determination of RA. The linear range was 10(-8) - 10(-5) M RA and the detection and quantification limits were 7.93 × 10(-9) M and 2.64 × 10(-8) M RA, respectively. The applicability of the developed method was tested by recovery studies and by the assessment of the total polyphenolic contents (TPCDPV) of green, white and black Turkish teas, which were found to be 40.74, 30.04 and 23.97 mg rosmarinic acid equivalent/g dry tea, respectively. These results were in good agreement with those obtained by the Folin-Ciocalteu method. The developed method is a sensitive and cheap tool for the rapid and precise evaluation of TPCDPV of tea samples.

Chemical Composition and Antipathogenic Activity of Artemisia annua Essential Oil from Romania.

The essential oil extracted by hydrodistillation from Romanian Artemisia annua aerial parts was characterized by GC/MS analysis, which allowed the identification of 94.64% of the total oil composition. The main components were camphor (17.74%), α-pinene (9.66%), germacrene D (7.55%), 1,8-cineole (7.24%), trans-ß-caryophyllene (7.02%), and artemisia ketone (6.26%). The antimicrobial activity of this essential oil was evaluated by determining the following parameters: minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), minimal fungicidal concentration (MFC), and minimal biofilm eradication concentration (MBEC). Moreover, the soluble virulence factors were quantified with different biochemical substrates incorporated in the culture media. The reference and resistant, clinical strains proved to be susceptible to the A. annua oil, with MICs ranging from 0.51 to 16.33 mg/ml. The tested essential oil also showed good antibiofilm activity, inhibiting both the initial stage of the microbial cell adhesion to the inert substratum and the preformed mature biofilm. When used at subinhibitory concentrations, the essential oil proved to inhibit the phenotypic expression of five soluble virulence factors (hemolysins, gelatinase, DNase, lipases, and lecithinases). Briefly, the present results showed that the A. annua essential oil contained antimicrobial compounds with selective activity on Gram-positive and Gram-negative bacterial strains as well as on yeast strains and which also interfere with the expression of cell-associated and soluble virulence factors.

Curcumin Electrochemistry-Antioxidant Activity Assessment, Voltammetric Behavior and Quantitative Determination, Applications as Electrode Modifier.

Curcumin (CU) is a polyphenolic compound extracted from turmeric, a well-known dietary spice. Since it has been shown that CU exerts beneficial effects on human health, interest has increased in its use but also in its analysis in different matrices. CU has an antioxidant character and is electroactive due to the presence of phenolic groups in its molecule. This paper reviews the data reported in the literature regarding the use of electrochemical techniques for the assessment of CU antioxidant activity and the investigation of the voltammetric behavior at different electrodes of free or loaded CU on various carriers. The performance characteristics and the analytical applications of the electrochemical methods developed for CU analysis are compared and critically discussed. Examples of voltammetric investigations of CU interaction with different metallic ions or of CU or CU complexes with DNA as well as the CU applications as electrode modifiers for the enhanced detection of various chemical species are also shown.

Voltammetric Investigation of Ferulic Acid at Disposable Pencil Graphite Electrode.

Ferulic acid (FA), a monohydroxycinnamic acid, is an antioxidant with multiple beneficial effects on human health, presenting also importance in the food and cosmetics industry. Its electrochemical behavior was investigated at the disposable and cost-effective pencil graphite electrode (PGE). Cyclic voltammetry emphasized its pH-dependent, diffusion-controlled oxidation. Using the optimized conditions (HB type PGE, Britton Robinson buffer pH 4.56) differential pulse and square-wave voltammetric techniques were applied for its quantitative determination in the range 4.00 × 10-7-1.00 × 10-3 mol/L FA. The developed methods were employed for the rapid and simple assessment of the FA content from a commercially available powder designed for cosmetic use.

Chemical and Biological Studies of Achillea setacea Herba Essential Oil-First Report on Some Antimicrobial and Antipathogenic Features.

The essential oil of Achillea setacea was isolated by hydrodistillation and characterized by GC-MS. The antioxidant and antimicrobial activity of Achillea setacea essential oil was evaluated, as well as its biocompatibility (LDH and MTT methods). DPPH, FRAP, and CUPRAC methods were applied for antioxidant activity evaluation, while qualitative and quantitative assays (inhibition zone diameter, minimum inhibitory concentration, and minimum fungicidal concentration), NO release (by nitrite concentration determination), and microbial adhesion capacity to the inert substrate (the biofilm microtiter method) were used to investigate the antimicrobial potential. A total of 52 compounds were identified by GC-MS in A. setacea essential oil, representing 97.43% of the total area. The major constituents were borneol (32.97%), 1,8-cineole (14.94%), camphor (10.13%), artemisia ketone (4.70%), α-terpineol (3.23%), and γ-eudesmol (3.23%). With MICs ranging from 0.78 to 30 µg/mL, the A. setacea essential oil proved to inhibit the microbial adhesion and induce the NO release. To the best of our knowledge, the present study reports for the first time the antimicrobial activity of A. setacea EO against clinically and biotechnologically important microbial strains, such as Shigella flexneri, Listeria ivanovii, L. innocua, Saccharomyces cerevisiae, Candida glabrata, Aspergillus niger, Rhizopus nigricans, Cladosporium cladosporioides, and Alternaria alternata, demonstrating its antimicrobial applications beyond the clinical field.

Past and Present of Electrochemical Sensors and Methods for Amphenicol Antibiotic Analysis.

Amphenicols are broad-spectrum antibiotics. Despite their benefits, they also present toxic effects and therefore their presence in animal-derived food was regulated. Various analytical methods have been reported for their trace analysis in food and environmental samples, as well as in the quality control of pharmaceuticals. Among these methods, the electrochemical ones are simpler, more rapid and cost-effective. The working electrode is the core of any electroanalytical method because the selectivity and sensitivity of the determination depend on its surface activity. Therefore, this review offers a comprehensive overview of the electrochemical sensors and methods along with their performance characteristics for chloramphenicol, thiamphenicol and florfenicol detection, with a focus on those reported in the last five years. Electrode modification procedures and analytical applications of the recently described devices for amphenicol electroanalysis in various matrices (pharmaceuticals, environmental, foods), together with the sample preparation methods were discussed. Therefore, the information and the concepts contained in this review can be a starting point for future new findings in the field of amphenicol electrochemical detection.

Electroanalysis of Naringin at Electroactivated Pencil Graphite Electrode for the Assessment of Polyphenolics with Intermediate Antioxidant Power.

A simple and rapid differential pulse voltammetric (DPV) method using a single-use electroactivated pencil graphite electrode (PGE*) is proposed for the rapid screening of the total content of polyphenolics (TCP) with intermediate antioxidant power (AOP) in grapefruit peel and fresh juice. The results were compared and correlated with those provided by the HPLC-DAD-MS method. NG voltammetric behavior at PGE* was studied by cyclic voltammetry and an oxidation mechanism was suggested. The experimental conditions (type of PGE, electroactivation procedure, pH, nature and concentration of supporting electrolyte) for NG DPV determination were optimized. The NG peak current varied linearly with the concentration in the ranges 1.40 × 10-6-2.00 × 10-5 and 2.00 × 10-5-1.40 × 10-4 mol/L NG and a limit of detection (LoD) of 6.02 × 10-7 mol/L NG was attained. The method repeatability expressed as relative standard deviation was 7.62% for the concentration level of 2.00 × 10-6 mol/L NG. After accumulation for 240 s of NG at PGE* the LoD was lowered to 1.35 × 10-7 mol/L NG, the linear range being 6.00 × 10-7-8.00 × 10-6 mol/L NG. The developed electrochemical system was successfully tested on real samples and proved to be a cost-effective tool for the simple estimation of the TCP with intermediate AOP in citrus fruits.

Facile Electrochemical Sensor for Sensitive and Selective Determination of Guaifenesin, Phenylephrine and Paracetamol on Electrochemically Pretreated Pencil Graphite Electrode.

Guaifenesin (GFS), phenylephrine (PHE) and paracetamol (PAR), drugs used in combination for the relief of cold and flu symptoms, were determined at electrochemically pretreated pencil graphite electrode. Differential pulse voltammetry (DPV) was used for the first time for the concomitant determination of the target compounds based on the electro-oxidation of PAR at 0.43 V, PHE at 0.74 V and GFS at 1.14 V in Britton-Robinson buffer pH 6.0. Under optimized experimental conditions, two linear ranges were obtained for PAR (2.50 × 10-6 M-1.00 × 10-5 M and 1.00 × 10-5 M-1.00 × 10-4 M) and for PHE and GFS linearity was proved between 5.00 × 10-6 M-2.00 × 10-4 M and 2.50 × 10-6 M-2.00 × 10-4 M, respectively. The detection limits were 8.12 × 10-7 M for PAR, 1.80 × 10-6 M for PHE and 8.29 × 10-7 M for GFS. The selective and sensitive DPV method and the electrochemically treated electrode were employed for simultaneous analysis of the analytes in pharmaceutical samples with good recoveries.

Bee Pollen Extracts: Chemical Composition, Antioxidant Properties, and Effect on the Growth of Selected Probiotic and Pathogenic Bacteria.

This paper evaluated the chemical and biological properties of bee pollen samples from Romania. Firstly, the bee pollen alcoholic extracts (BPEs) were obtained from raw bee pollen harvested by Apis mellifera carpatica bees. The chemical composition of BPE was obtained by determination of total phenol content and total flavonoid content, UHPLC-DAD-ESI/MS analysis of phenolic compounds, and GC-MS analysis of fatty acids, esters, and terpenes. Additionally, the antioxidant activity was evaluated by the Trolox Equivalent Antioxidant Capacity method. Furthermore, the biological properties of BPE were evaluated (antimicrobial and cytotoxic activity). The raw BP samples studied in this paper had significant phenolic acid and flavonoid content, and moderate fatty acid, ester, and terpene content. P1, P2, and P4 have the highest TPC and TFC levels, and the best antioxidant activity. All BPEs studied had antimicrobial activity on pathogenic strains isolated from the clinic or standard strains. A synergistic antimicrobial effect of the BPEs was observed along with the soluble compounds of L. rhamnosus MF9 and E. faecalis 2M17 against some pathogenic (clinical) strains and, considering the tumour proliferation inhibitory activity, makes BP a potential prebiotic and antitumour agent for the gut environment.

Disposable Pencil Graphite Electrode for Diosmin Voltammetric Analysis.

Diosmin (DIO) is a naturally occurring flavonoid with multiple beneficial effects on human health. The presence of different hydroxyl groups in diosmin structure enables its electrochemical investigation and quantification. This work presents, for the first time, diosmin voltammetric behavior and quantification on the cost-effective, disposable pencil graphite electrode (PGE). Diosmin oxidation on PGE involves two irreversible steps, generating products with reversible redox behaviors. All electrode processes are pH-dependent and predominantly adsorption-controlled. Differential pulse (DPV) and adsorptive stripping differential pulse (AdSDPV) voltammetric methods have been optimized for diosmin quantification o an H-type PGE, in 0.100 mol/L H2SO4. The linear ranges and limits of detection were for DPV 1.00 × 10-6-1.00 × 10-5 mol/L and 2.76 × 10-7 mol/L DIO for DPV and 1.00 × 10-7-2.50 × 10-6 mol/L and 7.42 × 10-8 mol/L DIO for AdSDPV, respectively. The DPV method was successfully applied for diosmin quantification in dietary supplement tablets. The percentage recovery was 99.87 ± 4.88%.

Actualities in immunological markers and electrochemical sensors for determination of dopamine and its metabolites in psychotic disorders (Review).

Psychotic disorders represent a serious health concern. At this moment, anamnestic data, international criteria for diagnosis/classification from the Diagnostic and Statistical Manual of Mental Disorders-5 and the International Classification of Diseases-10 and diagnostic scales are used to establish a diagnosis. The most commonly used biomarkers in psychotic illnesses are those regarding the neuroimmune system, metabolic abnormalities, neurotrophins and neurotransmitter systems and proteomics. A current issue faced by clinicians is the lack of biomarkers to help develop a more accurate diagnosis, with the possibility of initiating the most effective treatment. The detection of biological markers for psychosis has the potential to contribute to improvements in its diagnosis, prognosis and treatment effectiveness. The mixture of multiple biomarkers may improve the ability to differentiate and classify these patients. In this sense, the aim of this study was to analyze the literature concerning the potential biomarkers that could be used in medical practice and to review the newest developments in electrochemical sensors used for dopamine detection, one of the most important exploited biomarkers.

Current advances in metabolomic studies on non-motor psychiatric manifestations of Parkinson's disease (Review).

Life expectancy has increased worldwide and, along with it, a greater prevalence of age-dependent disorders, chronic illnesses and comorbidities can be observed. In 2019, in both Europe and the Americas, dementias ranked 3rd among the top 10 causes of death. Parkinson's disease (PD) is the second most frequent type of neurodegenerative disease. In the last decades, globally, the number of people suffering from PD has more than doubled to over 6 million. Of all the neurological disorders, PD increased with the fastest rate. This troubling trend highlights the stringent need for accurate diagnostic biomarkers, especially in the early stages of the disease and to evaluate treatment response. To gain a broad and complex understanding of the recent advances in the '-omics' research fields, electronic databases such as PubMed, Google Academic, and Science Direct were searched for publications regarding metabolomic studies on PD to identify specific biomarkers for PD, and especially PD with associated psychiatric symptomatology. Discoveries in the fields of metagenomics, transcriptomics and proteomics, may lead to an improved comprehension of the metabolic pathways involved in disease etiology and progression and contribute to the discovery of novel therapeutic targets for effective treatment options.

Rapid voltammetric method for quinine determination in soft drinks.

A novel voltammetric assay for quinine (QN) determination using an electrochemically pretreated pencil graphite electrode is described. The detection limit of QN was 2 × 10-7 M. The method possesses some obvious advantages including extreme simplicity, rapid response, and low cost.

Pencil Graphite Electrodes: A Versatile Tool in Electroanalysis.

Due to their electrochemical and economical characteristics, pencil graphite electrodes (PGEs) gained in recent years a large applicability to the analysis of various types of inorganic and organic compounds from very different matrices. The electrode material of this type of working electrodes is constituted by the well-known and easy commercially available graphite pencil leads. Thus, PGEs are cheap and user-friendly and can be employed as disposable electrodes avoiding the time-consuming step of solid electrodes surface cleaning between measurements. When compared to other working electrodes PGEs present lower background currents, higher sensitivity, good reproducibility, and an adjustable electroactive surface area, permitting the analysis of low concentrations and small sample volumes without any deposition/preconcentration step. Therefore, this paper presents a detailed overview of the PGEs characteristics, designs and applications of bare, and electrochemically pretreated and chemically modified PGEs along with the corresponding performance characteristics like linear range and detection limit. Techniques used for bare or modified PGEs surface characterization are also reviewed.

Studies on Chemical Composition and Antioxidant Activity of Rudbeckia triloba.

The paper describes the physicochemical studies made on the decorative plant, Rudbeckia triloba (Asteraceae). For this purpose, essential oil, infusion, decoction, and hydroalcoholic macerate obtained from different aerial parts of Rudbeckia triloba were analyzed. The main phytochemical constituents identified by GC-MS analysis were found to be α-pinene (in dried leaves (46.0%) and flowers (40.1%)) and ß-phellandrene (in essential oil of dried inflorescences (26.09%)). The Folin-Ciocalteu and quercetin assays revealed different values of total phenolic and flavonoid contents of petals, leaves, and seeds as a function of the solvent used and extraction procedure. The hydroalcoholic macerate of petals was found to present the maximum phenolic and flavonoid contents (130.29 ± 5.58 mg gallic acid equivalent/g dry vegetable material and 30.72 ± 1.35 mg quercetin equivalent/g dry vegetable material, resp.) and also exhibits the lower value of EC50 (0.32% (v/v)), obtained by applying the DPPH· assay. Comparing the extraction methods applied, the maceration was found to be the most effective for phenolic compounds, most likely due to the solvent (70% ethanol). The use of water-alcohol mixture leads to an improvement of the extraction yield of phenolic compounds (including those with higher molecular weights) than by using water as extractive solvent, in the case of infusions and decocts.

Comparative Chemical Analysis of Mentha piperita and M. spicata and a Fast Assessment of Commercial Peppermint Teas.

The hydrodistilled essential oils and volatile compounds (by static headspaces technique) of Mentha piperita L. and M spicata L. were characterized by GC-MS. Headspace analysis of Mentha piperita revealed the existence of menthone (25.4%), 1,8-cineole (17.7%) and menthol (12.1%) as the main components, while the essential oil contained high amounts of menthol (46.8%) and menthone (25.6%). By contrast, headspace analysis of M. spicata showed a high content of limonene (37.0%) together with carvone (13.0%), ß-pinene (10.4%) and α-pinene (9.8%), while the essential oil was reach in carvone (51.7%), dihydrocarveol (11.5%) and cis-dihydrocarvone (9.1%). Eleven samples of peppermint tea available on the Romanian market were analysed by headspace GC-MS. The volatile profile of the tea samples was compared with that of Mentha piperita L. and certain differences were emphasized and discussed.

Rapid determination of total polyphenolic content in tea samples based on caffeic acid voltammetric behaviour on a disposable graphite electrode.

The present paper describes the voltammetric behaviour and the quantitative determination of caffeic acid (CA) on a disposable pencil graphite electrode (PGE). The anodic peak current of CA recorded by differential pulse voltammetry (DPV) varies linearly with CA concentration in the range 1×10(-7)-3×10(-3) M. The detection and quantification limits were 8.83×10(-8) M and 2.94×10(-7) M caffeic acid, respectively. The mean recoveries of CA from Turkish green, white and black teas were 98.30%, 99.57% and 91.46%. For these three tea types the corresponding total polyphenolic contents (TPCs) evaluated by DPV on PGE were 35.81, 34.59 and 31.21 mg caffeic acid equivalent/g tea, respectively. These TPC values were in good accordance with those obtained by the Folin-Ciocalteu method. The developed DPV on PGE method constitutes a simple and inexpensive tool for the rapid assessment of TPC of tea samples.