Determination of the Total Polyphenols Content and Antioxidant Activity of <i>Echinacea Purpurea</i> Extracts Using Newly Manufactured Glassy Carbon Electrodes Modified with Carbon Nanotubes

• Main Authors: Florin Banica, Simona Bungau, Delia Mirela Tit, Tapan Behl, Pavel Otrisal, Aurelia Cristina Nechifor, Daniela Gitea, Flavia-Maria Pavel, Sebastian Nemeth
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Processes
• Subjects: polyphenols; antioxidant activity; <i>Echinacea purpurea</i> extracts; glassy carbon electrode (GCE); carbon nanotubes (CNTs)
• Online Access: https://www.mdpi.com/2227-9717/8/7/833

A sensitive electrochemical method was used for the determination of the total phenolic content and antioxidant activity <i>of Echinacea purpurea</i> extracts. In this study, 3 glassy carbon electrodes (GCE) were used: one unmodified and the other two newly manufactured glassy carbon electrodes modified with carbon nanotubes (CNTs) and chitosan (CS) in different concentrations, having the following composition: 1 mg/mL CNTs/CS 5%/GCE and 20 mg/mL CNTs/CS 0.5%/GCE. The determinations were performed on 3 different pharmaceutical forms (capsules, tablets and tincture), which contain <i>E. pururea</i> extract from the root or aerial part of the plant. Standard chicoric and caftaric polyphenolic acids, as well as food supplements extracts, were characterized using voltammetry, in a Britton-Robinson (B-R) electrolyte buffer. The modified 1 mg/mL CNTs/CS 5%/GCE electrode has superior properties compared to the other two (the unmodified and 20 mg/mL CNTs/CS 0.5%/GCE-modified) electrodes used in the study. <i>Echinacea</i> tincture had the highest antioxidant capacity and the biggest total amount of polyphenols (28.72 mg/equivalent of 500 mg powder). <i>Echinacea</i> capsules had the lowest antioxidant capacity, but also the lowest total amount of polyphenols (19.50 mg/500 mg powder); similarly, tablets had approximately the same values of polyphenols content (19.80 mg/500 mg powder), and also antioxidant capacity. The total polyphenol content was consistent with the one indicated by the manufacturers. Pulse-differential cyclic voltammetry represents a rapid, simple and sensitive technique to establish the entire polyphenolic amount and the antioxidant activity of the <i>E. purpurea</i> extracts.