Electrochemical quantification of the antioxidant capacity of medicinal plants using biosensors

• Published in: Sensors (Basel, Switzerland) Vol. 14; no. 8; pp. 14423 - 14439
• Main Authors: Rodríguez-Sevilla, Erika, Ramírez-Silva, María-Teresa, Romero-Romo, Mario, Ibarra-Escutia, Pedro, Palomar-Pardavé, Manuel
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 08-08-2014; MDPI
• Subjects: antioxidant capacity; Antioxidants; Antioxidants - chemistry; Biosensing Techniques - methods; Biosensors; Catechols - chemistry; Crosslinking; Electrical measurements; Electrochemistry - methods; Electrodes; Electrons; Enzymes; Enzymes, Immobilized - chemistry; Herbal medicine; Humans; immobilization; Lippia; Lippia alba; medicinal plants; Methods; Mexico; Michaelis-Menten constant; Monophenol Monooxygenase - chemistry; Plants (organisms); Plants, Medicinal - chemistry; Polyvinyl alcohol; Polyvinyl alcohols; Salvia; screen-printed electrodes; Sensors; tyrosinase; Mexico
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s140814423

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, Km', 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 Km' (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.