Melatonin is a hormone found in animals, plants, fungi, and bacteria, which can be used as a sleep aid and in the treatment of sleep disorders. Here, a rapid and accurate method was developed for the determination of melatonin in plasma, milk, and egg using high-performance liquid chromatography with fluorimetric detection (HPLC-FLD) and ultra high performance liquid chromatography-quadrupole-orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS). Sample was extracted with methanol and cleaned by passing through hydrophilic-lipophilic balanced (HLB) solid phase extraction cartridge. The method validation results showed that recovery for melatonin was between 80.3 and 105.1 % with relative standard deviations less than 9.8 %. UHPLC-Q-Orbitrap HRMS was employed as a further means of confirmation to assure accuracy of the results. Limits of detection for melatonin were 0.13 ng g −1 and 0.14 ng mL −1 for solid and liquid samples, respectively. Thus, the proposed method can be applied to detect melatonin in milk, plasma, and egg samples. Meanwhile, the metabolites of melatonin were identified using Q-Orbitrap HRMS. The approach identified five metabolites; among them, a novel metabolite, named mono-oxygenation-demethylation-melatonin, was found in plasma.

Purpose: To prepare and evaluate colon specific drug delivery system of diclofenac sodium for highly localized delivery to the colon.Methods: The colon specific drug delivery system was prepared as matrix-type microspheres using Ethyl Cellulose (EC), Cellulose Acetate Phthalate (CAP), and Eudragit L 100-55 by the Solvent Evaporation Method. Microspheres were evaluated for physical properties like drug content, particle size, bulk density and angle of repose.Results: The size range of the microcapsules was 228 to 608 μm while drug content was between 74.49 and 91.50 % depending on the polymer used and the  polymer ratio. Mean bulk density was < 1.2 g/ml which indicates the good flow properties, while angle of repose was < 40 o, indicating free-flowing properties. The microspheres were spherical in shape with smooth and nonporous surface, except that the microspheres containing EC and CAP exhibited a rough and porous  surface. The microspheres containing Eudragit L 100-55 in combination with other polymers gave better sustained release (78.9 and 76.6 % at the end of 8 h for  formulation F4 and F5, respectively) than the others.Conclusion: Microspheres prepared with drug: EC: CAP ratio of 1:2:1 show the highest drug content, possess good flow properties and surface morphology, as well as promising drug release for colon specific drug delivery of diclofenac sodium for possible treatment of colorectal cancer.Keywords: Diclofenac, Colorectal cancer, Microspheres, Ethyl cellulose, Cellulose acetate phthalate, Eudragit L 100-55