Determination of Melatonin in Rat Pineal Gland and Drug with Flow‐Injection Chemiluminescence

Abstract

A flow-injection chemiluminescence (CL) method for the determination of melatonin based on the CL reaction of melatonin with hydrogen peroxide and sodium hypochlorite (NaOCl) in a basic alkaline solution was developed. The possible CL mechanism has been discussed, and a proposal for the reaction pathway was given that singlet oxygen was clarified to be produced in this reaction system and was responsible for the CL emission. Under the optimized conditions, the linear concentration range of application was 1.0×10 -7 -2.5×10 -4 mol•L -1 with a detection limit of 5.0×10 -8 mol•L -1 (S/N＝3). The relative standard deviation for eight repeated measurements of 1.0 ×10 -6 mol•L -1 melatonin was 2.8%. The interferences of several important biological substances, some indole compound, cations and anions were studied. No interference was found for the anions, glucose, starch, most of cations and low concentration (less than 3.0×10 -6 mol•L -1 ) of some biological substances and indole compound. The method was applied to the determination of melatonin in rat pineal gland and drug with satisfactory results. The sample throughput was 90 injections per hour.

Dna Targeting as a Molecular Mechanism Underlying Endogenous Indoles Biological Effects

“…Similar results have also been reported by Wei et al following in vitro research on the interactions of gatifloxacin mesylate compounds (antibiotics from the fluoroquinolone class) and Mitoxantron (anti-tumour drug) with the DNA. It has been concluded that the masking of the fluorescent signal is due to an intercalation process of the studied compounds inside the DNA double strand [30]. The linearity of the graphs obtained in the assessment of the indoles-DNA interactions and the Stern-Volmer constants values reveal the existence of a single fluorophore agent, namely the indole molecules, in the analysed samples and prove the existence of a direct connection between DNA and the studied bio-indoles, as well as the affinity thereof for the formation of specific bonds with the DNA structure, process followed by the quenching of the samples' fluorescence.…”

“…The fluorescence quenching is a process which decreases the intensity of the fluorescent signal issued by the analysed sample. The literature describes 2 major processes of fluorescence quenching that can also take place simultaneously in the same sample: dynamic fluorescence quenching and static fluorescence quenching [30,32]. The dynamic fluorescence quenching is due to a diffusion process between the fluorophore agent (indole molecules) and the molecules triggering the florescence quenching (DNA).…”

“…Nevertheless, DNA interaction with several compounds fixed at the level of specific sites of the DNA structure is the starting point of some processes inducing the reversible or irreversible degradation of nucleic acids. Therefore, the study of the interaction between drugs or endogen key molecules and DNA plays a key role in elucidating biochemical mechanisms of action and it is of great significance for the synthesis of new therapeutic molecules targeted to DNA [1,15,[20][21][22][23][28][29][30]. In cancer therapy, small molecules are synthesized for binding to various parts of DNA by groove binding, via intercalation, cross-linking or even DNA strandscission [10,13].…”

Determination of Rifampicin by Peroxomonosulfate‐Cobalt(II) Chemiluminescence System

“…Chemiluminescence (CL), which owns excellent sensitivity, wide linear dynamic range and requires relatively simple and inexpensive instrumentation, is a powerful analytical technique. [15][16][17] Nowadays, the CL has been applied to the determination of rifampicin. Li et al 18 made use of continuous-flow chemiluminescence with artificial neural network calibration to carry out the simultaneous determination of the rifampicin and isoniazid, but both the relative standard errors and the detection limit were not satisfactory.…”