Simultaneous Electrochemical Monitoring of Metabolites Related to the Xanthine Oxidase Pathway Using a Grinded Carbon Electrode

Abstract

Using a mechanically grinded pyrolytic graphite electrode in edge orientation, a sensitive electrochemical method was developed for simultaneous determination of uric acid (UA), xanthine (XAN), hypoxanthine (HYP) (products of purine catabolism in human), allopurinol (ALO), and oxypurinol (OXY) (a drug used in treatment of purine catabolism disorders and its metabolite, respectively). It is demonstrated that differential pulse voltammetry in connection with this electrode can serve as a simple and efficient tool for monitoring transformation of purine catabolites (HYP --> XAN --> UA) catalyzed by xanthine oxidase (XO) as well as inhibition of this pathway by ALO being enzymatically converted to OXY. Our protocol is based on direct electrochemical measurement of oxidation peaks for each of the substances during in vitro reactions in a single detection step by the same electrode system. In addition, we show that the proposed electrochemical technique can be applied to parallel detection of metabolites involved in the XO pathway excreted in urine without any pretreatment of the clinical samples.

Voltammetric Study of Aminopurines on Pencil Graphite Electrode in the Presence of Copper Ions

“…An increasing number of amino groups results in a negative shift in E p . Similarly, the same effect was observed in a set of hydroxypurines (hypoxanthine, xanthine, uric acid) [42]. Addition of copper ions to the sample resulted in the appearance of peaks Ox com , which were lower compared to Ade Ox com .…”

Ru(DMSO)4Cl2 nano-aggregated Nafion membrane modified electrode for simultaneous electrochemical detection of hypoxanthine, xanthine and uric acid

“…X and X ? UA) on the working electrode interphase during the anodic sweep, which may further result in slight variation in the current signal of the fixed analytes [35]. Surface concentration of electro-active ruthenium species (C Ru ) were estimated by performing chrono-coulometric experiment in the respective analyte working potential windows and the values are; 0.0113 (0-0.5 V), 0.213 (0.4-0.9 V) and 0.793 Â 10 À12 mol cm À2 (0.6-1.1 V vs. Ag/AgCl) ( Fig.…”

“…In general, these methods are complicated, time consuming and several difficulties have been found to achieve satisfactory separation, sensitivity and enzyme stability. In this regard, few non-enzyme based electrochemical methods for the simultaneous detection of Hx, X and UA were reported till date, with examples being, unmodified glassy carbon electrode in 1 M H 2 SO 4 [32], carbon paste electrodes polarized in a dilute alkaline medium (2 mM NaOH + 10 mM NaClO 4 ) [33], pre-anodized (2 V vs. Ag/AgCl) Nontronite clay coated screen-printed electrode in pH 7.5 phosphate buffer solution (PBS) [34], grinded carbon electrode in pH 4.8 acetate buffer solution [35] and Nafion/lead-ruthenate pyrochlore chemically modified electrode (preliminary results) [36]. Unfortunately, existing electrodes were having complicated preparations along with series of surface activation and pre-concentration steps.…”

Electrochemical Detection of Uric Acid in Mixed and Clinical Samples: A Review

“…One simple method to enhance UA voltammetric sensing is to utilise mechanically ground carbon/graphite electrodes [61,62]. Both glassy carbon and pyrolytic graphite electrodes have been utilised and were modified by simple mechanical grinding using 15 mm silicon carbide particles.…”