Assessment of the degree of interference of polyphenolic compounds on glucose oxidation/peroxidase assay.
The glucose oxidase/peroxidase assay (GOP) is a coupled enzymatic assay commonly used in measuring glucose concentrations in biological sciences and food chemistry, particularly for quantification of α-glucosidase activity. However, we found that the GOP assay is prone to interference, especially from reducing substances such as polyphenolic compounds, which are commonly found in botanical materials. To establish the scope and limitation of the assay in measuring α-glucosidase inhibition activity, we systematically investigated the structural features of the polyphenolic compounds that can lead to false positives. Utilizing sodium dodecyl sulfate (SDS) as surrogate for the meriquinone intermediate formed during the reaction, we measured the reactivity of this redox active intermediate toward common flavonoids. Our results show that flavonoids with o-dihydroxy groups in the B-ring cause strong interference and that compounds with little DPPH scavenging activity do not have interference. Our results highlight the need for checking the suitability of the GOP assay first before it is applied in measuring α-glucosidase inhibition activity. In addition, when the literature data on α-glucosidase inhibition activity of botanical extracts or polyphenolic compounds using GOP assay are interpreted, potential false positives due to interference on the assay will need to be taken into consideration.
Food Science and Technology Program, Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore.
Adeline Ik Chian
AI
Wong
Dejian
D
Huang
D057075:Enzyme Assays; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D005949:Glucose Oxidase / Q000032:analysis* / Q000037:antagonists & inhibitors; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000032:analysis* / Q000037:antagonists & inhibitors; D059808:Polyphenols / Q000737:chemistry*
D004791:Enzyme Inhibitors; D059808:Polyphenols; D005949:Glucose Oxidase; D010544:Peroxidases; C023057:glucose peroxidase; D005947:Glucose