Desenvolvimento de biossensores eletroquimicos como ferramenta para avaliação da capacidade antioxidante de extratos vegetais / Development of electrochemical biosensors as a tool for evaluation of the antioxidant capacity of vegetables extracts

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

This work describes the development of two kind of electrochemical biosensors to evaluate the antioxidant capacity of vegetables extracts. The first biosensor developed was based on horseradish peroxidase immobilized on silica coated with titanium oxide and this material was employed to modify the carbon paste. In the optimized conditions, the biosensor response for total phenol content, was linear from 1 up to 50mmoI l in relation to the chlorogenic acid (CGA), with a sensitivity of 181 mmol l nA cm in 0.25 moI l phosphate buffer, pH 7.0. On the basis of the obtained recovery results, the biosensor showed to be suitable for the determination of polyphenols in tea and coffee (99 ± 4 % e 98 ± 2 %, respectively), because no significant influence of the matrix was observed. Total antioxidant activity (TAA) was obtained by the relationship between antioxidant activity and total phenol content, this parameter evaluated by using the biosensor. Antioxidant activities of the samples were investigated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. TAA of the tea extracts was obtained from relationships: TAA (Camellia sinensis) = 39 (± 3) [total phenol] + 2.5 (± 0.3) (r = 0.989); TAA (tea-type Ilex paraguariensis) = 0.8 (± 0.1) [total phenol] + 2.83 (± 0.60) (r = 0.986); TAA (herb-type Ilex paraguariensis) = 0.3 (± 0.1) [total phenol] - 0.4 (± 0.6) (r = 0.973). The measurements obtained by the biosensor was significant in terms of the total antioxidant activity (TAA). Another developed biosensor was based on a dsDNA (Calf thymus) layer immobilized on a screen-printed electrode (SPE). The biosensor was employed to verify the protection effect of tea extracts against DNA damage promoted by •OH radicals generated via Fenton-type reaction. The antioxidant activity was arranged in the order Baccharis gensteIloides >Peumus boldus >Foeniculum vulgare >Cymbopogom citratus >Camellia sinensis >Mentha piperita. A good repeatibility for the biosensor was demonstrated using the relative standard deviation (R.S.D.) of the measurements recorded (in triplicate) for all samples, the R.S.D. was 16 % (n = 6). The results demonstrated that the DNA-based biosensor is suitable as a rapid screening test for evaluation of the antioxidant properties of samples in a direct way, easy and low-cost.

ASSUNTO(S)

acido desoxirribonucleico antioxidantes dna biosensores biosensors antioxidants

ACESSO AO ARTIGO

Documentos Relacionados