Gut microbiota in neurological diseases: Melatonin plays an important regulatory role.

Melatonin is a highly conserved molecule produced in the human pineal gland as a hormone. It is known for its essential biological effects, such as antioxidant activity, circadian rhythm regulator, and immunomodulatory effects. The gut is one of the primary known sources of melatonin. The gut microbiota helps produce melatonin from tryptophan, and melatonin has been shown to have a beneficial effect on gut barrier function and microbial population. Dysbiosis of the intestinal microbiota is associated with bacterial imbalance and decreased beneficial microbial metabolites, including melatonin. In this way, low melatonin levels may be related to several human diseases. Melatonin has shown both preventive and therapeutic effects against various conditions, including neurological diseases such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis. This review was aimed to discuss the role of melatonin in the body, and to describe the possible relationship between gut microbiota and melatonin production, as well as the potential therapeutic effects of melatonin on neurological diseases.

Determination of Enrofloxacin and Ciprofloxacin Residues in Five Different Kinds of Chicken Tissues by Dispersive Liquid-Liquid Microextraction Coupled with HPLC.

Contamination of food producing animals by veterinary drug residues, particularly quinolones, is an essential issue in food safety that causes increasing concern in consumers. The aim of this study was to investigate the occurrence of enrofloxacin and its main metabolite, ciprofloxacin, in chicken tissue samples slaughtered in Tabriz, Iran. Totally 250 samples including liver, muscle, gizzard, heart, and skin were studied. Dispersive liquid-liquid microextraction technique (DLLME) was used as a simple, high performance, low-cost, and fast sample pre-treatment method followed by a high-performance liquid chromatography with UV detection for quantitative analysis. The residues of enrofloxacin were detected and quantified in 26 liver (52%) and 10 skin (20%) samples and ciprofloxacin residues were detected in 3 skin (6%) samples and accurately determined in 15 liver (30%) samples; however they were not detected in gizzard, heart, and muscle samples. The results showed the accumulation of enrofloxacin and ciprofloxacin residues in chicken liver and skin.

Dispersive Liquid-Liquid Microextraction for HPLC-UV Determination of PAHs in Milk.

A simple and rapid analytical method for the extraction and quantification of four polycyclic aromatic hydrocarbons in milk sample has been developed using dispersive liquid-liquid microextraction followed by the use of HPLC. Benzo(a)pyrene, benzo(a)anthracene, and benzo(b)fluoranthene were used as model compounds; the milk sample was spiked with these compounds to assess the extraction procedure. Experimental parameters that influence the extraction efficiency, including the nature and volume of the disperser and extraction solvents, pH, and the volume of milk sample, were optimized. Under the optimum extraction conditions (extraction solvent: chloroform, 200 µL; dispersive solvent: acetonitrile, 700 µL; and extraction time 5 s or less), the performance of the proposed method was evaluated. The chromatographic peak area was linear with concentrations in the range of 0.2-10 ng/mL(-1) and with correlation coefficients ranging from 0.9968 to 0.9985. The LODs, based on a S/N ratio of 3, ranged from 0.06 to 0.18 ng/mL(-1). The RSDs varied from 3.68 to 9.7% (n = 3). The recoveries of these compounds were from 88.38 to 100%. The performance of the present method was evaluated for the determination of polycyclic aromatic hydrocarbons in various types of milk samples.

Optimized Dispersive Liquid-Liquid Microextraction Method and High Performance Liquid Chromatography with Ultraviolet Detection for Simultaneous Determination of Sorbic and Benzoic Acids and Evaluation of Contamination of These Preservatives in Iranian Foods.

A rapid, simple, and sensitive dispersive liquid-liquid microextraction procedure followed by HPLC-UV was applied to determine the benzoate and sorbate in foods. The method was optimized for some variables including extraction solvent type and volume, dispersing solvent type and volume, and the effects of salt and pH. Optimum conditions were determined as follows: sample volume, 5 mL; extraction solvent (chloroform) volume, 250 µL; disperser solvent (acetone) volume, 1.2 mL; NaCl amount, 0.75 g/5 mL at pH 4. Sixty samples were analyzed, including 15 doogh, 15 fruit juice, 15 cookie, and 15 tomato paste; benzoic acid was detected in 57 samples (95%) at levels up to 448.1 µg/mL and sorbic acid in 31 samples (51.6%) at levels up to 1369 µg/mL. Under the optimum experimental conditions, the LOD and LOQ were determined as 0.1 and 0.5 µg/mL for benzoate and 0.08 and 0.3 µg/mL for sorbate, respectively. The results showed that these preservatives are commonly used at high levels in yogurt drinks (dooghs) and cookies. Also, the concentration of benzoic acid that was detected in the tomato paste and fruit juice samples was low but may affect children and sensitive persons.

Benzoic and sorbic acid in soft drink, milk, ketchup sauce and bread by dispersive liquid-liquid microextraction coupled with HPLC.

Benzoic acid and sorbic acid are widely used for food preservation. These preservatives are generally recognised as safe. The aim of this study was to determine the level of benzoic and sorbic acid in food samples that are usually consumed in Iran. Therefore, 54 samples, including 15 soft drinks, 15 ultra-high-temperature milk, 15 ketchup sauces and 9 bread samples, were analysed by high-performance liquid chromatography with UV detection. Benzoic acid was detected in 50 (92.5%) of the samples ranging from 3.5 to 1520 µg mL⁻¹, while sorbic acid was detected in 29 (50.3%) samples in a range of 0.8 and 2305 µg mL⁻¹. Limits of detection and limits of quantification for benzoate were found to be 0.1 and 0.5 µg mL⁻¹, respectively, and for sorbate 0.08 and 0.3 µg mL⁻¹, respectively. The results showed that benzoic acid and sorbic acid widely occur in food products in Iran.

Single dose bioequivalence study of alpha-methyldopa tablet formulations using a modified HPLC method.

BACKGROUND AND OBJECTIVE: The purpose of the present study was to compare the bioavailability of a new methyldopa (CAS 555-30-6) tablet formulation with that of a reference formulation in 12 healthy male subjects using a modified HPLC method. METHODS: The study was designed as an open label, single-dose, randomized study with a cross-over design. Under fasting conditions, each subject received one 250-mg tablet orally as a single dose of a test or reference formulation on two treatment days. The treatment periods were separated by a one-week washout period. The blood samples were collected at different time points after each administration and determined using a rapid and reliable modified HPLC method. The method used was validated for specificity, accuracy, precision and sensitivity. The pharmacokinetic parameters (Cmax, AUC0-t, AUC0-infinity) were statistically compared by analysis of variance (ANOVA) for test and reference formulations. RESULTS AND DISCUSSION: All validation criteria for the developed HPLC method were in acceptable range. The maximum plasma concentration (Cmax) of alpha-methyldopa was 270.3-1864.9 ng/ml for the test and 224.5-1585.6 ng/ml for the reference formulation. The mean AUC0-infinity of alpha-methyldopa was 2002.1-10614.8 and 2076.8- 9056.3 ng x h/ml for the test and reference formulation, respectively. The calculated 90% confidence intervals for the mean test/reference ratios of mentioned parameters were 92.48-115.94, and 88.82-101.13 which are in the bioequivalence range. The statistical tests did not show any statistical differences between formulations suggesting that methyldopa tablet of test and reference can be considered as bioequivalent preparations. CONCLUSION: A rapid and reliable HPLC method with fluorescence detector was developed to analyze alpha-methyldopa in human plasma. Based on the obtained results the test formulation of alpha-methyldopa is bioequivalent to the reference formulation.

Intracerebroventricular administration of riluzole prevents morphine-induced apoptosis in the lumbar region of the rat spinal cord.

Opiates are the most effective drugs for pain relief. However, the repeated use of opiates induces tolerance to their analgesic effects. It has been shown that this morphine-induced tolerance is associated with apoptosis in the central nervous system. The aim of this study is to evaluate the effects of intracerebroventricular (i.c.v.) administration of riluzole, an anti-glutamatergic drug, on morphine-induced apoptosis in the lumbar region of the rat spinal cord. Animals were given daily injections of morphine and vehicle, morphine and riluzole, or riluzole alone. Nociception was assessed using a hot plate apparatus, and apoptosis was assessed using the in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method. The levels of anti-apoptotic factors Bcl-2 and HSP 70 and the pro-apoptotic agent caspase-3 were evaluated using immunoblotting. The glutamate concentration in the lumbar spinal cord was measured with high performance liquid chromatography (HPLC). The results indicate that the i.c.v. administration of riluzole attenuated morphine tolerance and reduced the number of TUNEL positive cells. Immunoblotting revealed that the levels of the selected anti-apoptotic agents were greater in the treatment groups compared to the controls. Furthermore, the results demonstrated that the administration of riluzole can attenuate the morphine-induced elevation of glutamate in the lumbar spinal cord. In conclusion, i.c.v. administration of riluzole attenuated morphine-induced tolerance to analgesia and apoptosis in addition to preventing the morphine-induced increase of glutamate in the lumbar spinal cord of rats.

Development of a simple and sensitive high-performance liquid chromatography method for determination of glucosamine in pharmaceutical formulations.

A column high-performance liquid chromatography (HPLC) method was developed for the determination of glucosamine in dosage forms. Glucosamine was derivatized by addition of a solution containing orthophthaldialdehyde. The HPLC separation was achieved on a Spherimage 80 ODS2 column (250 x 4 mm id, 5 microm particle size) using an isocratic mobile phase containing phosphate buffer-methanol (90 + 10, v/v, pH 6.50) and methanol-tetrahydrofuran (97 + 3, v/v) in proportions of 85 + 15 at a flow rate of 1 mL/min, followed by fluorescence detection. The method was validated for specificity, linearity, accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ). The detector response for glucosamine HCI was linear over the concentration range of 0.1-20 microg/mL with a correlation coefficient of 0.9980. The accuracy was between 99.4 and 100.8%. The LOD and the LOQ were 0.009 and 0.027 microg/mL, respectively. The method was applied to determination of glucosamine in solid dosage forms.

Preparation of glucosamine from exoskeleton of shrimp and predicting production yield by response surface methodology.

Chitin was prepared from Persian Gulf shrimp (Metapenaeus monoceros), and then, the obtained chitin was hydrolyzed by hydrochloric acid solutions. The production yield of glucosamine hydrochloride from chitin was optimized, and the effect of three factors (acid concentration, acid to chitin ratio, and reaction time) was investigated. A Box-Behnken design by Minitab software created 12 reactions with different conditions. Each reaction was performed in two replicates. Response surface methodology was used for predicting the glucosamine preparation. The optimum conditions for glucosamine hydrochloride preparation were 30 and 37% hydrochloric acid, 9:1 (v/w) acid solution to solid ratio, and 4 h of reaction time. Time ratio and time acid concentrations were the effective factors on the yield.