Electrochemical Quantification of the Antioxidant Capacity of Medicinal Plants Using Biosensors

Author： Rodríguez-Sevilla Erika Ramírez-Silva María-Teresa Romero-Romo Mario Ibarra-Escutia Pedro Palomar-Pardavé Manuel

Publisher： MDPI

E-ISSN： 1424-8220|14|8|14423-14439

ISSN： 1424-8220

Source： Sensors, Vol.14, Iss.8, 2014-08, pp. : 14423-14439

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Abstract

The working area of a screen-printed electrode, SPE, was modified with the enzyme tyrosinase (Tyr) using different immobilization methods, namely entrapment with water-soluble polyvinyl alcohol (PVA), cross-linking using glutaraldehyde (GA), and cross-linking using GA and human serum albumin (HSA); the resulting electrodes were termed SPE/Tyr/PVA, SPE/Tyr/GA and SPE/Tyr/HSA/GA, respectively. These biosensors were characterized by means of amperometry and EIS techniques. From amperometric evaluations, the apparent Michaelis-Menten constant, K_m′, of each biosensor was evaluated while the respective charge transfer resistance, Rct, was assessed from impedance measurements. It was found that the SPE/Tyr/GA had the smallest K_m′ (57 ± 7) μM and Rct values. This electrode also displayed both the lowest detection and quantification limits for catechol quantification. Using the SPE/Tyr/GA, the Trolox Equivalent Antioxidant Capacity (TEAC) was determined from infusions prepared with “mirto” (Salvia microphylla), “hHierba dulce” (Lippia dulcis) and “salve real” (Lippia alba), medicinal plants commonly used in Mexico.