Cholesterol (C₂₇H₄₆O) is a lipid-derived substance found in lipoproteins and cell membranes. It is also one of the main sources for the production of bile acids, vitamin D, and steroid hormones. Today, foods are evaluated by consumers not only according to their taste and nutritional content but also according to their effects on consumer health. For example, many consumers choose foods according to their cholesterol level. The cholesterol in the food can directly affect the blood cholesterol level when consumed, which can lead to cardiovascular diseases. High levels of cholesterol can lead to diet-related human diseases such as cardiac arrest, paralysis, type II diabetes, and cerebral hemorrhage. In societies with high living standards, interest in and consumption of foods that lower or have low cholesterol levels have increased recently. Accordingly, efforts to increase the variety of foods with reduced cholesterol levels are on the rise. This has indirectly led to the accurate measurement of cholesterol levels in blood and food being of great importance. Classical chemical, enzymatic, colorimetric, polarographic, chromatographic, and spectrophotometric methods; enzymatic, nonenzymatic, and electrochemical sensors; and biosensors are used for the determination of cholesterol in foods. The purpose of this review is to reveal and explore current and future trends in cholesterol detection methods in foods. This review will summarize the most appropriate and standard methods for measuring cholesterol in biological components and foods.

In this study, bromocresol purple was electropolymerized on the surface of a pencil graphite electrode (PGE) and electrochemically doped with cerium (Ce) nanoparticles. The Ce-doped poly­(bromocresol purple) (Ce/PBCP)-modified PGE was characterized using energy dispersive X-ray spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The prepared Ce/PBCP electrode was investigated for the electrochemical determination of melatonin in the presence of dopamine. The electrochemical activity of the Ce/PBCP electrode was compared with that of undoped PBCP, Ce/PGE, and bare PGE. The peak potential and peak current for melatonin oxidation were +800 mV and 820 μA cm^–2, respectively. The detection limit of melatonin was 0.038 μM, and the Ce/PBCP electrode exhibited high activity in the presence of interfering species. In addition, the use of a Ce/PBCP electrode for detecting melatonin in a terebinth sample, a real food sample, was also investigated, and the produced electrode demonstrated high performance.

In this study, Ag nanoparticles decorated poly(l-cysteine) (PCs) electrodes (Ag@PCs) were developed for the non-enzymatic determination of H₂O₂. Additionally, the electrochemical synthesis of Ag@PCs nanostructures on the pencil graphite electrode surface was achieved for the first time. Different techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy were used in the analytical and morphological characterization of the produced Ag@PCs modified electrodes. As-prepared Ag@PCs electrodes were examined as electrode materials in the non-enzymatic determination of H₂O₂. Electrochemical determination of H₂O₂ was investigated using cyclic voltammetry and chronoamperometry techniques. While the detection limit of the sensor was 0.26 µM, its sensitivity and linear range were calculated as 142.47 μA μM⁻¹ and 250−3560 µM, respectively. Moreover, high selectivity towards H₂O₂ was achieved in the presence of interfering species at the Ag@PCs electrode. Ag@PCs electrodes have great potential for applications involving the electrochemical detection of H₂O₂.

The objective of this study was to investigate the possibility of using natural and bacteria-modified Erzurum clayey soil with Methylobacterium extorquens as an alternative to high cost commercial adsorbent materials for the removal of copper from aqueous solution. The copper concentrations in the samples of the polluted river water and CuCl₂ solutions treated by the natural and bacteria-modified Erzurum clayey soil (ECS) have been determined by spectrophotometric method. Firstly, the surface of ECS was modified with M. extorquens and surface functionality was increased. Then, the adsorption of Cu (II) from solution phases was studied with respect to varying metal concentration, pH, and temperature and agitation time. The maximum adsorption of Cu (II) for natural and bacteria-modified Erzurum clayey soil was observed at pH: 5.0. At different copper concentrations, copper adsorption analysis was performed on 1 g using clay soil or modified clay soil. Maximum adsorption of Cu (II) was obtained as 45.7 and 48.1 mg g^-1 at initial concentration (50 mg/50 mL) and optimal conditions by natural and bacteria-modified clay soil, respectively. The copper concentration was decreased in the substantial amount of the leachates solutions of natural and bacteria-modified clay soil. Langmuir and Freundlich isotherms were used to describe the adsorption behavior of Cu (II) ions. The results showed that modified clay soil had a high level of adsorption capacity for copper ion. The various thermodynamic parameters such as ΔG°, ΔH° and ΔS° were analyzed to observe the nature of adsorption. The structural properties of the natural and bacteria-modified-ECS have been characterized by SEM, FTIR and XRD techniques. Consequently, it was concluded that the bacteria-modified clay soil could be successfully used for the removal of the copper ions from the aqueous solutions.

Cholesterol is a lipid-derived substance found in lipoproteins and cell membranes. It is also one of the main sources for the production of bile acids, vitamin D, and steroid hormones. Today, foods are evaluated by consumers not only according to their taste and nutritional content but also according to their effects on consumer health. For example, many consumers choose foods according to their cholesterol level. The cholesterol in the food can directly affect the blood cholesterol level when consumed, which can lead to cardiovascular diseases. High levels of cholesterol can lead to diet-related human diseases such as cardiac arrest, paralysis, type II diabetes cerebral hemorrhage. In societies with high living standards, interest in and consumption of foods that lower or have low cholesterol levels have increased recently. Accordingly, efforts to increase the variety of foods with reduced cholesterol levels are on the rise. This has indirectly insulted in accurate measurement of cholesterol levels in blood and food being of great importance. Classical chemical, enzymatic, colorimetric, polarographic, chromatographic, spectrophotometric methods, and enzymatic, nonenzymatic, and electrochemical sensors and biosensors are used for the determination of cholesterol in foods. The purpose of this review is to reveal and explore current and future trends in cholesterol detection methods in foods. The review will summarize the most appropriate and standard methods for measuring cholesterol in biological components and foods.

Melatonin is an important hormone with a methoxy-indole structure. It is secreted regularly by the pineal gland of mammals. It takes part in many chemical, biological, and physiological activities of the body. Melatonin, acts as a basic hormone, and is responsible for circadian rhythm regulation and sleep control. It has been shown to occur in the highest concentration in organisms during the night times. In living organisms, many activities that have physiological, biological, hormonal, and psychological characteristics follows a certain rhythm. Body temperature, hormone levels, sleep-wakefulness, and some other cognitive functions in humans also change with the circadian rhythm. Its synthesis and release begin with darkness and end with light. This review aims to explore the functions of melatonin such as its stimulating effects on antioxidant enzymes, reducing lipid peroxidation, and protecting brain tissue from oxidative damage. It also has properties that stop the proliferation of cancer cells and prevent tumor growth. Melatonin, which was previously known only as an animal hormone, has been found to also exist in plants. Research has shown that melatonin is present in almost all plant species analyzed to date and that it performs functions similar to those in animals. In plants, it plays a vital role in dealing with various abiotic and biotic stresses. Melatonin acts as an important antioxidant in post-harvest technology and extends the post-harvest life of fruits and vegetables. It also takes part in the regulation of stress-specific genes and the activation of pathogenesis-related proteins and antioxidant enzymes. The most prominent roles of melatonin in plants include regulating circadian rhythm, growth, and development, and increasing tolerance to a wide range of environmental stress factors. The review reveals the effects of melatonin as an extremely important secondary metabolite, on human, animal, and plant metabolism. The use of PRISMA guidelines was used for reporting, search, selection, and synthesis. Information up to 2024 was searched from search engines for the occurrence, nature and function of melatonin. Key words such as structural function, hormonal function, secretion and metabolism were used in the search of publications.