Kenan Can Tok

In this study, a capillary electrophoresis (CE) method was developed for the determination of naltrexone, an opioid antagonist, and its primary metabolite, 6‐β‐naltrexol (6‐β‐NTX). Naltrexone is commonly used in the treatment of opioid and alcohol dependence. Accurate quantification of such drugs and their metabolites is essential for ensuring therapeutic efficacy and safety. Reliable determination of NTX and 6‐β‐NTX in plasma is important for bioanalytical and clinical investigations involving naltrexone therapy. Method optimization was carried out using Box–Behnken design within the framework of response surface methodology to achieve maximum resolution between naltrexone and 6‐β‐naltrexol. Separation was performed at 15°C using a 10 mM phosphate buffer (pH 2.0) under an applied voltage of 20 kV, without the addition of organic modifiers. The method was validated in accordance with bioanalytical validation guidelines, providing a validated lower limit of quantification (LLOQ) of 0.05 µg/mL for both analytes, with precision (% relative standard deviation [RSD]) below 7% at the LLOQ. The validated method was successfully applied to plasma samples obtained from patients receiving treatment for alcohol and opioid use disorders. Furthermore, the environmental sustainability of the proposed CE method and its sample preparation steps was assessed using green analytical chemistry metrics, such as AGREE, AGREEprep, and MoGAPI, demonstrating its greener profile compared to reported methods.

Lactiplantibacillus plantarum is a member of lactic acid bacteria that improves the quality of fermented foods while also having a positive impact on human health. In this study, L. plantarum F2 was studied for characteristics such as biochemical and genetic identification, metabolite production, antimicrobial activity, and plasmid content. This strain exerts antimicrobial activity against some Gram-positive and Gram-negative pathogens ( Listeria monocytogenes , Staphylococcus aureus , Salmonella , and Escherichia coli ) with inhibition zone diameters ranging between 17.0 and 29.0 mm; it can ferment glucose, arabinose, galactose, lactose, and demonstrated the ability to grow at high temperature (50°C). Another physiological specification of the strain was the morphology of the isolate in selective medium, the de Man, Rogosa, Sharpe medium (MRS medium containing triphenyl tetrazolium chloride), which exhibits a chromogenic colony (characterized as purple colonies) on the modified-MRS (mMRS) medium. Metabolites such as lactic acid and diacetyl production of the strain F2 were also investigated using chromatography and found to be 10.07 and 0.05 µg/mL, respectively. The peptides of the isolate’s cell-free supernatant were determined to be ∼80 kDa, and finally, the plasmid isolated from the strain F2 was identified as L. plantarum strain KLDS1.0386 plasmid p4, which may be responsible for some characteristic properties, such as antimicrobial peptide production of the strain.

Objective: To develop and validate a rapid, sensitive, and cost-effective HPLC-UV method for the quantification of pregabalin (PRG) in both bulk drug substance and pharmaceutical dosage formulations, addressing the growing need for robust analytical techniques in pharmaceutical quality control and forensic toxicology. Material and Method: An HPLC-UV method was developed using an Agilent 1100/1200 system equipped with a UV detector and a Merck monolithic silica column (100 mm x 4.6 mm). The mobile phase consisted of acetonitrile and water (5:95, v/v) adjusted to pH 7.0 with orthophosphoric acid and sodium hydroxide, at a flow rate of 2.0 ml/min and a column temperature of 45°C. UV detection was set at 200 nm. The method was validated according to ICH Q2(R1) guidelines, evaluating linearity, sensitivity, accuracy, precision, recovery, and stability-indicating properties through forced degradation studies. Result and Discussion: The developed HPLC-UV method demonstrated rapid analysis with a pregabalin retention time of 1.44 minutes and a total run time under 2 minutes. System suitability parameters met pharmacopeial requirements. The method exhibited excellent linearity in the range of 1 to 150 µg/ml (R² > 0.999), with LOD and LOQ values of 0.25 µg/ml and 0.76 µg/ml, respectively. Intra-day and inter-day accuracy ranged from 96.09% to 99.68% and 95.07% to 98.78%, respectively, with RSD values for precision consistently below 2.22%. Recovery from pharmaceutical formulations was between 99.0% and 101.75%. Forced degradation studies revealed that pregabalin is stable under acidic, oxidative, and thermal stress conditions, as well as during freeze-thaw and autosampler storage, but is susceptible to base hydrolysis. The validated HPLC-UV method is demonstrated to be rapid, accurate, precise, and stability-indicating, making it suitable for routine quality control of pregabalin in pharmaceutical products and for forensic applications.

Recent studies indicate that niclosamide demonstrates considerable promise as both an anthelmintic agent and a possible anticancer medication. Given the increasing interest in nano-sized drug delivery methods for cancer therapy, lipid nanocapsules (LNCs) have emerged as a viable approach to enhance the bioavailability of poorly soluble pharmaceuticals due to their beneficial properties. This research intends to develop niclosamide-loaded lipid nanocapsules (NIC-LNCs) using the phase inversion technique, followed by the optimization of these formulations via the Box-Behnken experimental design. A reverse-phase high-performance liquid chromatography (RP-HPLC) method was devised and validated for quantifying niclosamide in the LNC formulations. Optimal chromatographic separation was attained utilizing an Agilent Eclipse XDB-C18 column (150×4.6 mm, 5 µm i.d.) with a mobile phase of a 50:50 (v/v) mixture of acetonitrile and 0.1% H3PO4 phosphate buffer, at a flow rate of 1.2 mL/min. The detection wavelength was set at 335 nm, and the analysis was performed at 35°C. The developed analytical methodology was validated through a comprehensive evaluation of accuracy, linearity, precision, limit of detection, limit of quantitation, specificity, and stability. The optimization of the NIC-LNC formulation through the Box-Behnken design resulted in an optimal formulation labeled LNC5, consisting of 4% niclosamide, 20% lipid, and 20% surfactant. The proven RPHPLC method enables accurate quantification of NIC in the LNC formulations. The refined NIC-LNC formulation exhibited developed attributes as assessed by the design. The findings indicate that LNC systems are a promising method for drug administration, especially for anticancer drugs with limited solubility in water.

In the present study, lactic acid bacteria (LAB) isolated from various fermented food sources, were studied on their antimicrobial properties alongside quantifying the production levels of lactic acid and diacetyl. Based on the findings of 16S rRNA sequencing, Pediococcus spp. were identified in 4 out of 11 isolates, Lactiplantibacillus spp. in 2 isolates, Leuconostoc spp. in 2 isolates, and Enterococcus spp. in 3 isolates. Except for isolate 8, all tested isolates demonstrated inhibitory effects against the pathogens used in the antimicrobial activity assays conducted in this study. Isolate F2 exhibited the highest lactic acid production, reaching a concentration of 10.07 mg/mL, while isolate 8 showed the highest diacetyl production at 0.8 µg/mL. Particularly, strains 40, 50, F2, AF1, and AF2 exhibited significant lactic acid production and demonstrated strong antimicrobial effects. Consequently, isolates exhibiting elevated levels of lactic acid production also demonstrated heightened antimicrobial effects, suggesting a contributory role of lactic acid production in antimicrobial activity.

One health is an approach that gains importance in the protection of public health and advocates that the environment-animal-human health is linked. Microbial resistance occurring in any of these three factors circulates directly or indirectly between species and affects health. In this study, antimicrobial, anti-quorum sensing activity and potential probiotic properties of Lactobacillus acidophilus and Enterococcus faecalis 1 and 2 isolates from Apis mellifera gut were investigated. Results showed that isolates were found to be resistant to gentamicin, streptomycin, erythromycin, and clindamycin tested. It was determined that isolates were gamma haemolytic and resistant to acid and enzymatic environment conditions. Enterococcus faecalis isolates had antimicrobial activity on Escherichia coli ATCC 25922, Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853 and anti-quorum sensing activity of the culture supernatants of all isolates was detected by a violacein pigment inhibition of Chromobacterium violaceum strain.

In this study, the antibacterial activity of methanol and acetone extracts of Chlorella sp. was examined. The chemical contents of the extracts were clarified by GC/MS analysis. Antibacterial activity of Chlorella sp. extracts was determined as a minimum inhibitory concentration by broth microdilution method against Bacillus subtilis ATCC 6633, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213. It was found that methanol and acetone extracts of Chlorella sp. showed antibacterial activity against B. subtilis ATCC 6633 (625 µg/ml and 1250 µg/ml, respectively), E. faecalis ATCC 29212 (>5000 µg/ml and 1250 µg/ml, respectively), E. coli ATCC 25922 (>5000 µg/ml), P. aeruginosa ATCC 27853 (>5000 µg/ml), S. aureus ATCC 29213 (2500 µg/ml) at the specified concentrations. In the chemical analysis of the extracts, it was determined that the fatty acids were in high amounts, 33.22% and 40.41%, respectively, in the methanol and acetone extracts. Among the alternative methods to show activity against pathogenic microorganisms, algae can be a good natural resource. This study showed that Chlorella sp. contains high fatty acids and has potential as an antibacterial agent of natural origin.

Amaç: Silene L. (Caryophyllaceae) türleri geleneksel olarak iltihap, idrar yolu iltihabı, göz rahatsızlığı, cilt sorunu, mide ağrısı, dizanteri, diş çürümesi, ateş, baş ağrısı, sıtma, sivilce ve sırt ağrısı tedavisinde kullanılmaktadır. Silene türlerinin kimyasal bileşenleri flavonoidler, antosiyanidinler, terpenoidler, triterpen saponinler, fitoekdisteroidler, benzenoidler, vitaminlerden oluşur ve antioksidan, antiinflamatuar, antitümör, antiviral aktivite gösterirler. Silene ruscifolia (Hub.-Mor. & Reese) Hub.-Mor. Türkiye'de "gizli nakıl" olarak adlandırılır.Gereç ve Yöntem: Bitki materyali Beynam Ormanı'ndan (Ankara/Türkiye) toplandı. Bitkinin toprak üstü kısımları ultrasonik banyoda metanol ile ekstre edildi. Otomatik örnekleyici, ikili pompa, kolon fırını ve bir UV dedektörüne sahip HPLC sistemi (Agilent 1260 Serisi), Çift Sprey Agilent Jet Stream elektrosprey iyonizasyon kaynağına sahip bir iFunnel Quadrupole Time-of-Flight LC-MS system (Agilent G6550A) ile birleştirildi. Bileşiklerin ayrılması için Agilent TC C-18 (4.6 mm x 150 mm x 5 µm) kolonu kullanıldı. Ekstrenin GC-MS analizi, bir Agilent 5973N dört kutuplu kütle spektrometresi (Agilent, ABD) ile donatılmış bir Agilent 6890 gaz kromatografı kullanılarak yapıldı. Bileşiklerin belirlenmesi ve tanımlanması için Mass Hunter yazılımı (Qualitative Analysis B.07.00) ve NIST Mass Spectral Library (2014) kullanıldı.Sonuç ve Tartışma: LC-MS Q-TOF analizi, S. ruscifolia'nın rutin, narsissin, luteolin, izoramnetin, ramnetin ve kersetin dimetil eter içerdiğini gösterdi. GC-MS analizi, ekstrenin şeker (%50.5) ve şeker alkolleri (%46.39) olarak en yüksek içeriğe sahip olduğunu göstermiştir. Ayrıca karboksilik asit (%0.47), yağ asidi (%0.64), şeker asidi (%0.42), glikozit (%0.48), karotenoidler (%0.61) ve benzoik asit esteri (%0.49) içerir. D-pinitol, %41.14 ile ekstredeki en yüksek içeriğe sahiptir.

In a recent study, opposite enantiomer elution order was observed for ketoprofen enantiomers on two amylose-phenylcarbamate-based chiral columns with the same chemical composition of the chiral selector but in one case with coated while in the other with an immobilized chiral selector. In the present study, the influence of this uncommon effect on method validation parameters for the determination of minor enantiomeric impurity in dexketoprofen was studied. The validated methods with two alternative elution orders for enantiomers were applied for the evaluation of enantiomeric impurity in six marketed dexketoprofen formulations from various vendors. In most of these formulations except one the content of enantiomeric impurity exceeded 0.1% (w/w).