Mustafa Özyürek

1. Piperazine substituted compounds have attracted great attention for synthetic chemists for their importance in drug design as they show antibacterial activities against a wide variety of pathoge...

Aronia melanocarpa (black chokeberry) is a fruit rich in phenolic compounds and well-known for its potent antioxidant capacity; however, comparative investigations comparing fresh berries and their processed counterparts remain scarce. In this work, microwave-assisted extraction (MAE) was optimized via response surface methodology (RSM) to enhance the recovery of antioxidant constituents from Aronia fruits cultivated in Türkiye. Extraction time (5–30 min), temperature (40–100 °C), solvent-to-solid ratio (mL/0.1 g dry sample, DS), and solvent composition (20–100%) were systematically modeled, while antioxidant performance was assessed using the CUPRAC assay. The optimal conditions (100 °C, 24 min, 34% ethanol, 14 mL per 0.1 g DS) yielded a maximum TAC value of 0.998 mmol TE/g DS. Both raw fruits and commercial preparations (juice, concentrate, dried fruit, jam, vinegar, gummies, herbal capsules) were then characterized by spectrophotometric assays (CUPRAC, Folin–Ciocalteu, pH differential) and by chromatographic analysis (HPLC-PDA). Major anthocyanins—including cyanidin-3-O-xyloside, cyanidin-3-O-arabinoside, cyanidin-3-O-glucoside, and cyanidin-3-O-galactoside—and phenolics such as chlorogenic acid, neochlorogenic acid, epicatechin, and gallic acid were identified and quantified. Substantial compositional differences were observed between fresh fruit and processed products, with pronounced losses of anthocyanins attributed to industrial processing. This study provides the first integrated assessment of Turkish Aronia fruits and related commercial products, by uniting MAE optimization with comprehensive antioxidant and phytochemical profiling, and offering new insights into their nutritional and functional potential.

Hypochlorous acid (HOCl) is a potent nonradical oxidant involved in various physiological processes, particularly within the human immune system. In this study, we introduce a novel, rapid, and highly efficient fluorometric method for the detection of HOCl. The method utilizes a near-infrared (NIR)-based fluorescent probe, NIR-QBH, which is characterized by its high sensitivity and chemical stability. NIR-QBH, containing olefinic C=C bonds, exhibits strong NIR emission at 660 nm (λex = 618 nm). The detection mechanism relies on the oxidation of the C=C bond in the NIR-QBH structure by HOCl, resulting in the formation of non-fluorescent products. With a detection limit of 0.23 μM, the probe demonstrates a fast response time of 4 min. Glutathione (GSH), an essential biothiol, was employed as a reference HOCl scavenger, and its HOCl scavenging activity was evaluated with an IC50 value of 8.97 μM. Furthermore, the developed fluorometric assay was successfully applied for the detection of HOCl in fetal bovine serum (FBS) and aqueous solutions.

Detection of intracellular biothiols (cysteine (CYS), N-acetyl cysteine (NAC) and glutathione (GSH)) with high-selectivity and sensitivity is important to reveal biological functions. In this study, 2-(2-methoxy-4-methylphenoxy)-3-chloro-5,8-dihydroxynaphthalene-1,4-dione (3) (DDN-O) compound was newly synthesized and used as a fluorogenic probe (detector molecule) in the fluorometric method for the rapid, highly selective and sensitive determination of biothiols. The intensity values (λex = 260 nm, λem = 620 nm) of the product were measured by adding biotihols to the reaction medium at varying concentrations and the glutathione equivalent thiol content (GETC) values of each biotiol were calculated. Using the compoud (3), the reference biotiol GSH was detected in the linear concentration range of 10-70 μM and the LOD value was found to be 0.11 μM. Biothiol detection with the structurally simple compoud (3) was performed at the cellular level within 1 min, and this probe has also been successfully used in bioimaging with low citotoxicity. It is evaluated that this probe can be an alternative to existing fluorescence-based biothiol probes, can be used in rapid biothiol detection at the cellular level in biological functions. To evaluate the molecular structure of (3), conformational analysis was performed using the PM3 semi-empirical method. The obtained most stable molecular geometry was then optimized at DFT/wb97xd/6-311++G(d,p) level of theory. Frontier molecular orbitals (HOMO and LUMO) and molecular electrostatic potential (MEP) map analyses were performed for the optimized structure. The molecular docking studies demonstrated the interactions of (3) with HAS (1AO6) and FhGST (2FHE) target proteins.

1. In recent years, the importance of preventing reactive oxygen species (ROS) from damaging macromolecules such as protein, lipid and DNA in living organisms under oxidative stress conditions has ...

Measurement uncertainty is a metrological concept that characterizes distributions/variations that can make the measurement results logical and is linked to the result of the measurement. The measurement uncertainty of the method was estimated using two basic approaches (top-down and bottom-up approach). The top-down approach covers in-house validation data (trueness, repeatability and intra-lab reproducibility), while the bottom-up approach involves individual contributions to all uncertainty at each stage of the analysis/process. We estimated measurement uncertainty of BPA analysis by HPLC-FLD test according to JCGM GUM and EURACHEM-CITAC guidelines. The relative expanded uncertainties at the BPA concentration by the bottom-up approach and top-down approaches were ±3.2% and ±4.8% respectively (95% confidence interval, k=2). Thus, although it is seen that the results of the two approaches are different in chromatographic BPA analysis, it is concluded that the measurement uncertainty related to BPA analysis, especially in food analysis laboratories, can be determined by a simpler top-down approach.

As the carrier of various inorganics and organics from various media, micro(nano)plastics have an impact on the environment and human health. Recently, many studies have examined the sorption of various organics including antibiotics. However, while vitamins have critical roles in the environment and microsystems from humans to plant life, the sorption of vitamins onto micro(nano)plastics are still uninvestigated. Therefore, the aim of this study was to examine the sorption of vitamin B1 onto various micro(nano)plastics from food packages under different pHs using batch technique; sorption kinetics and isotherms models were investigated as well. The results indicated that higher capacities were obtained between 360 min to 1440 min in polypropylene and polyethylene micro(nano)plastics, and similar kinetic behaviors observed in different pHs. However, the sorption responses (sorption capacity, equilibrium time) of polyethylene terephthalate and polystyrene were varied. The sorption kinetics between vitamin B1 and micro(nano)plastics showed that the pseudo-first-order model was better to fit for polyethylene terephthalate and polystyrene compared to the pseudo-second-order kinetics, however it was changed for polypropylene and polyethylene. Moreover, the obtained results suggest a complex nature of vitamin B1 sorption, including both chemical and physical sorption occur under various pHs and polymer types.

The estimation of uncertainty –taking into account all sources of error- is an important tool allowing the identification the influence of each stage of the analytical procedure on the overall quality of the results. Measurement uncertainty - reported with the measurement result - is a parameter that indicates the distribution of the probabilities attributable to the measurement results. The aim of this study is the first time estimation of measurement uncertainty for total antioxidant capacity (TAC) of a Turkish commercial apple juice by the main CUPRAC method that uses Cu(II)-neocuproine (Nc)/Cu(I)-Nc redox couple to measure the TAC levels of various biological fluids and foods. The individual source of uncertainties such as repeatability, calibration curve, concentration of the trolox (TR, reference) solutions, pH, temperature and redox factor in the CUPRAC reaction between TR and Cu(II)-Nc were considered in this work. It was found that the measurement uncertainty was dominantly affected by the total CTR standard solution (ur(CTR) =0.0124). Each uncertainty parameter was evaluated separately, and the relative expanded uncertainty value was calculated as ±3.05% with a 95% confidence interval (k=2).