Sensitive and fast beverage/fruit antioxidant evaluation by TiO2 -Au/graphene nanocomposites coupled with MALDI-MS

Because the ratio of tripeptide glutathione (GSH) to glutathione disulphide (GSSG) is tightly associated with the oxidative stress and antioxidant level of an organism, it is often considered to be an indicator of the redox states of cells. Therefore, developing an integrated protocol for rapid, efficient, and low-cost detection of GSH to measure antioxidant ability is of significant importance for the diagnosis of oxidative stress-associated diseases.

TiO2 -Au/graphene nanocomposites were synthesized to integrate the characteristics of graphene as matrix for MALDI-MS, gold NPs as selective probes for GSH and the photocatalytic property of TiO2 . Under UV-visible (UV-Vis) light irradiation, OH can be produced by the TiO2 -Au/G composites, which can oxidize GSH to form GSSG. When various antioxidants are introduced into the aforementioned system, OH can be scavenged, thereby leaving part of GSH in its reductive format. Based on the ratio of GSH/GSSG, the antioxidative capability of various beverages and fruits can be determined.

TiO2 -Au/G composites were employed to enrich GSH, where 0.01 mg/mL GSH can be efficiently extracted by the nanocomposites from aqueous solution and detected by MS with high signal-to-noise ratio. The proposed strategy was applied to evaluate three often-used antioxidants: Vitamin C, Vitamin E, and β-carotene; and demonstrated that the antioxidative ability of VC is the strongest. To further evaluate the feasibility of the proposed strategy for antioxidative ability evaluation of complex sample, commercial juices and fresh fruit were also studied.

A novel strategy for sensitive and fast characterization of the antioxidative ability of various beverages and fruits was developed based on TiO2 -Au/G nanocomposites coupled with MALDI-MS. Copyright © 2016 John Wiley & Sons, Ltd.