Determination of free concentration of endocannabinoids in brain tissue.

The release of metabolites from their bound to free forms is the main regulatory path in living species. Therefore, the ability to determine the free concentrations of small molecules is highly critical in many biological samples. The main challenges in achieving this task are the interferences inherent to complex matrices and the ability to distinguish between the free and total concentrations. This paper presents a non-invasive microextraction method that enables the determination of endocannabinoids in brain tissue. The proposed method is based on two key principles: the availability of the free concentration of endocannabinoids for partitioning to the solid-phase microextraction (SPME) fiber; and negligible depletion enabled by the small volume of extraction phase on the fiber. These features allow the presented SPME method to provide information about the free concentration of analytes without disturbing the binding equilibrium between the analytes and the matrix. The determination of spiked samples with known concentrations enables the percentage of analyte bound to the tissue to be calculated, which can then be applied to calculate the total concentration from the determined free concentration. This manuscript focuses on the determination of the free concentration and tissue binding percentages of endocannabinoids in brain tissue. Significantly, SPME's small size and potential for non-invasive sampling enable its application in live animal subjects with minimal tissue damage.

Standard Water Generating Vials for Lipophilic Compounds.

The study of non-polar compounds in aqueous environments has always been challenging due to their poor solubility in aqueous media. The low affinity of non-polar compounds toward polar solutions facilitates their attachment to glassware, which results in unstable sample concentrations. To address this challenge, and to enable the preparation of a stable mixture of hydrophobic compounds in an aquatic environment, we introduce an in-vial standard water generating system consisting of a vial containing appropriate aqueous solution and a polydimethylsiloxane thin film spiked with target compounds. In this system, a solution with a stable analyte concentration is attained once equilibrium between the thin-film and aqueous solution has been achieved. The developed standard water system was studied using endocannabinoids and phospholipids as model hydrophobic compounds of biological importance, with results indicating that the concentration of hydrophobic compounds in water can remain stable over multiple days. The results also showed that analytes released from the thin film can compensate for analyte loss due to extractions with solid-phase microextraction fibers, thereby re-establishing equilibrium. Thus, the vial is suitable for the repeatable generation of non-polar standards for routine analysis and quality control. The results of this work show that the developed system is stable and reproducible and therefore appropriate for studies requiring the measurement of free concentrations and accurate quantification.

Determination of fingerprints contents of different extracts and parts of six endemic Salvia taxa by GC-MS: Source species for valuable compounds with drug or drug potential.

Public use of Salvia species and their importance in the scientific world is continually increasing. It is known that this use and the importance of Salvia species are mostly due to the terpenoid compounds that they contain. In this context, the terpenoid-steroid-flavonoid contents of extracts of six endemic Salvia (S. kurdica, S. pseudeuphratica, S. rosifolia, S. siirtica, S. cerino-pruinosa var. cerino-pruinosa and S. cerino-pruinosa var. elazigensis) species prepared with different solvents were determined by gas chromatography-mass spectrometry. Within the framework of the ingredient analysis, content analysis of the ethanol extracts of the root, branch, leaf and flower parts of the species collected in the same period between 2015 and 2017 years was performed. In general, extracts prepared with chloroform and ethanol were found to contain a wide variety of compounds while petroleum ether extracts were found to contain much less varied compounds. In addition, in general, root extracts are richer in terpenoid compounds than aerial part extracts. Some species can be used as source species in terms of ferruginol, cryptanol, 6,7-dehydroroyleanone, lup-(20)29-ene-2α-hydroxy-3ß-acetate, salvigenin and ß-sitosterol contents (52,114.28, 75,979.08, 101,247.41, 40,071.29, 33,952.13 and 34,010.90 µg analyte/g extract, respectively).

A High-Performance Liquid Chromatographic Method for the Determination of Meropenem in Serum.

In this study, a new, sensitive and selective high-performance liquid chromatographic method was developed for the determination of meropenem (MEM) in human serum. In the developed method, C18 column (3.9 × 150 mm, 5 µm) was selected as stationary phase at 30°C, and methanol: acetic acid solution mixture was used as mobile phase with gradient program. Chromatographic separation was carried out at a flow rate of 1 mL/min, and detection was performed at 300 nm with diode array detector. Doripenem was selected as an internal standard, and the analytes were extracted from serum using protein precipitation method with ortho-phosphoric acid: methanol. Detection wavelength was selected as 300 nm. The developed method was validated according to International Council for Harmonisation (ICH) guidelines. The calibration curve was linear over a concentration range of 4-240 µg/mL with correlation coefficient of 0.9985. The limit of detection and limit of quantification values were found as 0.057 and 0.192 µg/mL, respectively. The validated method was successfully applied for the determination of MEM in human serum samples collected from patient volunteers at different time intervals, and therapeutic drug monitoring of MEM has been investigated.