Evaluation of the total antioxidant capacity of Anchusa italica retz using carbon fiber microelectrode modified by Au-Ag alloy urchin-like nanostructures.

Anchusa italica Retz, a plant rich in bioactive compounds, has garnered considerable attention for its antioxidant properties and associated health benefits. However, the traditional methods for assessing antioxidant capacity often suffer from limited sensitivity and operational complexity. To overcome these challenges, gold-silver alloy urchin-like nanostructures (AAA-UNs) were synthesized using an ascorbic acid reduction method and electrodeposited onto a carbon fiber microelectrode (CFME) to form a highly sensitive electrochemical sensor (AAA-UNs/CFME). The morphology and structure of the synthesized material and modified electrode were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Sensor performance was optimized using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The antioxidant capacity of Anchusa italica Retz was evaluated by monitoring changes in the electrochemical behavior of guanine (used as a model biomolecule) upon exposure to Fenton-generated hydroxyl radicals (·OH), with and without the protective presence of antioxidants. The AAA-UNs/CFME exhibited high sensitivity, stability, and anti-interference capability, achieving a detection limit of 0.05 mmol/L and a linear range of 0.3-3.0 mmol/L for guanine. Experimental results confirmed that Anchusa italica Retz extracts from different geographic origins possess significant antioxidant activity. Among these, the Xinjiang Anchusa italica Retz extract showed the highest radical scavenging efficiency (81.05%), followed by samples from Pakistan (69.63%) and Hainan (60.26%). These findings underscore the innovative application of the AAA-UNs/CFME sensor for reliable, rapid and sensitive assessment of antioxidant capacity in complex botanical samples.