A Nanoparticle-Based Label-Free Sensor for Screening the Relative Antioxidant Capacity of Hydrosoluble Plant Extracts

Abstract

One of the most important aspects of the detection of antioxidant compounds is developing a fast screening method. The screening of the overall relative antioxidant capacity (RAC) of several Romanian hydrosoluble plant extracts is the focus of this work. This is important because of the presence of increasing levels of reactive oxygen species (such as H2O2) generates oxidative stress in the human body. The consequences are a large number of medical conditions that can be helped by a larger consumption of plant extracts as food supplements, which do not necessarily contain the specified antioxidant contents. By exploiting the catalytic properties of gold nanoparticles, a specific and sensitive nanoparticle-based label-free electrochemical sensor was developed, where the working parameters were optimized for RAC screening of hydrosoluble plant extracts. First, electrochemical measurements (cyclic voltammetry and amperometry) were used to characterize different nanoparticle-based sensors, revealing the best performance of gold nanoparticle-based sensors, obtaining a RAC of 98% for lavender extracts. The sensing principle is based on the quenching effect of antioxidants for H2O2 amperometric detection, where the decrease in electrical signal suggests an increasing antioxidant capacity. The obtained results were expressed in terms of ascorbic acid and Trolox equivalents in order to be able to correlate our results with classical methods like chemiluminescence and UV-Vis spectrophotometry, where a correlation coefficient of 0.907 was achieved, suggesting a good correlation between electrochemistry and spectrophotometry. Considering these results, the optimized gold nanoparticle-based label-free sensor can be used as a simple, rapid alternative towards classical methods for relative antioxidant capacity detection of hydrosoluble plant extracts.

Ethnopharmacological Value and Biological Activities via Antioxidant and Anti-Protein Denaturation Activity of Morinda lucida Benth and Momordica charantia L. Leaves Extracts from Benin

“…Electrochemical methods, such as voltammetry and amperometry, have been used to determine the total antioxidant capacity of the extracts [ 47 , 48 , 49 ]. The open circuit potential (OCP), which measures the equilibrium potential at the electrode surface, can be used to quantify a samples’ redox potential, which is a function of its composition [ 50 ]. It was registered in this study and the results obtained with M. charantia and M. lucida indicate that the overall redox potential of both plant extracts in methanol have no significant difference.…”

Antioxidant Determination with the Use of Carbon-Based Electrodes

“…The antioxidant capacity reflects the conversion of the reactive oxygenated species that is scavenged. This illustrates the scavenging ability, and can be expressed as the amount, as moles, of the scavenged free radical by antioxidants [15,16], present in an analyzed sample, for instance a plant extract [17]. The term "antioxidant activity" is prevalent in electrochemical approaches, that directly provide informations about analyte concentration.…”

Biosensors for Antioxidants Detection: Trends and Perspectives

“…Nanoparticles are widely used to either improve the enzymatic catalytic activity, enhance biosensor selectivity or gain more control over the electrode microenvironment [ 13 , 16 , 44 ]. Carbon-based nanomaterials such as single- or multi-walled carbon nanotubes (SW-, MW-CNT), carbon nanofibers are available on a large scale and are most often incorporated into biosensor architectures.…”

“…The antioxidant capacity of phenols depends on their redox properties, which depend on the presence of a phenolic aromatic ring with hydroxyl substituents in their chemical structure. It is well known that anodic peaks at low oxidation potentials (below ~ 0.5 V) occur for compounds with significant antioxidant activity [ 13 ], while, at potentials greater than +0.6 V, all phenolic compounds will be oxidized [ 12 ]. Some major benefits of AOx are described in the literature.…”