Xanthine is an intermediate of the purine nucleotide and deoxynucleotide metabolism and present in most of our body tissues and fluids [1]. The normal concentration of xanthine in human plasma ranges from 0.5 to 2.5 μM (40−160 μM in urine) [2]. As the metabolic precursor of uric acid, xanthine is the first indicator of an abnormal purine profile and can serve as a marker of many diseases including hyperuricemia[3], gout[4], xanthinuria[5], perinatal asphyxia[6], cerebral ischemia[7], tumor hyperthermia[8] and pre-eclampsia[9]. Uric acid is typically present at serum concentrations of ∼200−400 μM and is by far the dominant purine of this class in biological fluids [10-15]. Hypoxanthine is the precursor to xanthine and is typically present at plasma concentrations of ∼10−30 μM in healthy humans [15].
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The accumulation of xanthine is at the expense of uric acid whose concentrations are very low [2]. In the food industry xanthine is also an important biomarker. Inosine monophosphate (present in fresh fish samples) degrades (by microbial action or the action of other endogenous enzymes) to inosine, then to hypoxanthine and xanthine. Elevated levels of hypoxanthine and xanthine are a sign of spoilage [16]. Thus, developing a stable, sensitive, and selective of hypoxanthine/xanthine sensor may also has applications in food quality control. Widely employed assays for xanthine oxido reductase activity are spectrophotometric quantitation of uric acid, the final product of the reaction [20] quantitation of hypoxanthine, xanthine or uric acid by high performance liquid chromatography (HPLC)
The accumulation of xanthine is at the expense of uric acid whose concentrations are very low [2]. In the food industry xanthine is also an important biomarker. Inosine monophosphate (present in fresh fish samples) degrades (by microbial action or the action of other endogenous enzymes) to inosine, then to hypoxanthine and xanthine. Elevated levels of hypoxanthine and xanthine are a sign of spoilage [16]. Thus, developing a stable, sensitive, and selective of hypoxanthine/xanthine sensor may also has applications in food quality control. Widely employed assays for xanthine oxido reductase activity are spectrophotometric quantitation of uric acid, the final product of the reaction [20] quantitation of hypoxanthine, xanthine or uric acid by high performance liquid chromatography (HPLC)