Electrocatalytic Oxidation and Determination of Morin at a Poly(2,5-dimercapto-1,3,4-thiadiazole) Modified Carbon Fiber Paper Electrode

Abstract

Voltammetric determination of morin on carbon fiber paper (CFP) electrode modified by electropolymerization of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) in phosphate buffer solution (PB, pH 9.0) have been studied. This modified electrode showed strong electrocatalytic activity toward the oxidation of morin, a flavonoid at physiological pH (PB, pH 7.0). Morin gave a sensitive anodic peak at 0.245 V (vs. SCE). The parameters influencing the anodic peak of morin such as effect of pH, effect of scan rate and concentration have been optimized. The electrochemical process was found to be irreversible and adsorption-controlled. Under the optimum conditions, the anodic peak current was linear to concentration of morin in the range of 2.5 × 10 −10 -2.75 × 10 −9 M and detection limit was found to be 8.3 × 10 −11 M. The practical application of the modified electrode was successfully demonstrated for the determination of morin in mulberry leaves.Flavonoids consist of a broad group of polyphenol compounds that are characterized by the presence of a benzene-γ-pyrone structure. They are naturally occurring antioxidants present in plants. 1 Flavonoids are increasingly appreciated for being an important component in the human diet due to their ability to prevent various diseases. One of the most common flavonols present in nature, morin (3,2,4,5,7-pentahydroxyflavone) is, originally isolated from members of the Moraceae family, such as mulberry, figs and some traditional Chinese medicinal herbs. These phenolic secondary metabolites are widely distributed in plants, fruits, flowers and plant-derived foods like tea, coffee and cereal grains. 2,3 Morin possesses various biological and biochemical effects including antitumor, anti-inflammatory, antiviral, antiallergic and cardioprotective activities. 4 Epidemiological studies indicate that adequate intake of flavonoid-rich foods may decrease the risk of coronary heart disease and certain cancers. 5,6 Morin inhibits the growth of COLO205 cells in nude mice, 8 exhibits intestinal anti-inflammatory activity in the acute phase of trinitrobenzenesulfonic acid model of rat colitis and exhibits chemopreventive effects on chemically induced rat tongue carcinogenesis. 9,10 Morin is a potent antioxidant and has excellent metal ion chelating capacity. The antioxidant activity of morin can be explained in direct scavenging of singlet oxygen species and inhibition of enzymes involved in the production of reactive oxygen species. 11,12 The chelating ability of morin with low valent metal ions makes it a good antioxidant as the latter is capable of catalysing peroxidation of lipids and promote oxidation of other biological molecules. 13 It has been reported that the antioxidant activity of morin is due to its chemical structure (Scheme 1). 14 The structure of morin consists of two aromatic rings namely A and B which are linked by an oxygen containing heterocycle C. Ring B with m-hydroxyls at positions 2 and 4 is the radical target site of morin. The additional hydroxyl groups present at 5 and 7 posi...

Highly Productive Synthesis, Characterization, and Fluorescence and Heavy Metal Ion Adsorption Properties of Poly(2,5-dimercapto-1,3,4-thiadiazole) Nanosheets

“…Accordingly, it is desirable to synthesize poly(2,5-dimercapto-1,3,4-thiadiazole) (PBT) as a promising adsorbent for heavy metal ions. However, the chemical oxidative polymerization of the 1,3,4-thiadiazole ring containing derivatives has been demonstrated to be very difficult, though the electrochemical polymerization method has proved to be feasible [18,19]. Sun, Qin, and coworkers [20,21,22] have attempted to synthesize a 1,3,4-thiadiazole ring containing polymers by using the chemical oxidative method, but merely obtained metal coordination polymers instead of genuine polymers like polypyrrole and polythiophene.…”

β-Cyclodextrin-PANI decorated pencil graphite electrode for the electrochemical sensing of morin in almonds and mulberry leaves

“…Literature study shows that not many electrochemical methods are available for the analysis of morin. Electrochemically prepared electrodes for determination of morin include vanadium pentoxide nanoflake film decorated glassy carbon electrode (GCE) [11], polyvinylpyrolidone (PVP) doped carbon paste electrode, Pt electrode [12], bare glassy carbon electrode (GCE) [13] and hanging mercury drop electrode [14], Ir decorated poly(3,4-ethylenedioxythiophene) on carbon fiber paper (Ir-PEDOT/ CFP) [15], 2,5-dimercapto-1,3,4-thiadazole modified carbon fiber paper (p-DMTD/CFP) [16] are also reported. An electrochemical sensing method with molecular imprinting mechanism using Pd nanoparticles-porous graphene carbon nanotubes (CNTs)/GCE has also been listed for quercetin [17].…”

Determination of morin on an electrochemically activated carbon-paste electrode

“…These sensors are based on a glassy carbon electrode modified with carboxylated nanotubes; 9 a composite of graphene oxide, poly-3,4-ethylenedioxythiophene, and gold nanoparticles; 10 1-butyl-3-methylimidazoliumhexafluorophosphat and chitosan; 11 poly(tetrafluroethylene)-deoxyribonucleate acid; 12 and vanadium pentoxide. 13 Sensors developed based on a mixture of carbon nanotubes and paraffin oil, 14 renewable pencil electrodes 15 , and carbon fiber paper electrode modified with poly(2,5-dimercapto-1,3,4-thiadiazole) 16 were also proposed (comparative characteristics of the proposed sensors are presented in Table 1). In the above studies it was established that, in the determination of morin, the oxidation current has a predominantly adsorptive character.…”