DNA damage in a solution containing copper(II) ions and ascorbic acid: Effect of the presence of sulfite

Some antioxidant compounds have a pro-oxidant effect in the presence of transition metal ions, due to the reduction of Mn+ to M(n-1)+ with simultaneous formation of free radicals, which then promote DNA damage. In the present study, we evaluated the pUC19 DNA damage in a solution containing Cu(II) and ascorbic acid (AA) or S(IV) saturated with air by agarose gel electrophoresis. Our results showed that this damage decreases if AA and S(IV) are simultaneously added. This study also illustrates the importance of Cu(II) in this process, as no DNA damage was observed when AA or S(IV) were present in the absence of this metallic ion. Our data showed that DNA preservation depends on the concentration of AA and S(IV) and occurs when the [S(IV)]:[AA] ratio ranges from 1:1 to 20:1. Absorbance measurements and thermodynamic data show that no reaction occurs between AA and S(IV) when this mixture (pH 5.5) is added to pUC-19 DNA. The presence of dissolved oxygen may be the cause of AA consumption in the mixture of these two antioxidants, which subsequently decreases DNA damage.

Determinação da atividade antioxidante e do teor total de polifenol em amostras de chá de ervas comercializadas em sachets / Determination of total antioxidant activity and total content of polyphenols in samples of tea leaves marketed in bags

OBJETIVO: Os chás de ervas são tradicionalmente utilizados na medicina popular em muitas regiões do Brasil. Os chás contêm compostos antioxidantes que combatem o stress oxidativo e seu consumo tem sido associado à diminuição dos níveis de colesterol, pressão arterial e até de doenças cardiovasculares. O objetivo deste estudo foi determinar a capacidade antioxidante total, o teor total de polifenóis, o consumo (scavenging) de H2O2 e a presença de outros grupos de compostos antioxidantes em 43 amostras de chás em sachets. MÉTODOS: O método CUPRAC (cupric ion reducing antioxidant capacity) foi utilizado para determinar a capacidade antioxidante total. O teor total de polifenóis foi obtido com o uso do reagente de Folin-Ciocalteu; o ensaio de scavenging baseou-se no consumo de solução de H2O2 após adição do chá; e a presença de flavonóides, carotenos e catequinas foi investigada por cromatografia em papel. RESULTADOS: A capacidade antioxidante total nas amostras analisadas seguiu a ordem: camomila > hortelã > carqueja >cidreira > boldo > verde > mate > preto > branco > erva doce. O teor total de polifenóis obedeceu à sequência: branco > hortelã > preto > mate > boldo > verde > camomila > carqueja > cidreira > erva doce. As divergências encontradas entre as amostras de um mesmo grupo de chá podem ser atribuídas à época da colheita, ao tipo de solo, local de plantio, variações climáticas e partes da planta utilizadas na elaboração dos sachets. CONCLUSÃO: Conclui-se que todas as amostras analisadas apresentaram capacidade antioxidante e consumo de H2O2. Em apenas uma delas não foi possível detectar flavonóides, carotenos ou catequinas.

OBJECTIVE: Tea leaves are traditionally used in folk medicine in many regions of Brazil. They contain antioxidant compounds that can protect against oxidative stress and their regular intake have been associated with decreased of cholesterol levels, blood pressure and, thereby, with the lowered risk of coronary heart disease. The objective of this study was to determine the total antioxidant capacity, the total polyphenols content,scavenging of H2O2 and presence of other groups of antioxidant compounds in 43 tea samples packed in bags. METHODS: The CUPRAC method (cupric ion reducing antioxidant capacity) was used to quantify the total antioxidant capacity. The polyphenols content was performed using the Folin-Ciocalteu reagent. The scavenging assay was based on the consumption of H2O2 after addition of tea; the presence of flavonoids, carotenes and catechins was evaluated by paper chromatography. RESULTS:The total antioxidant capacity found in tea samples followed the order: chamomile > mint > carqueja > balm > boldo > green > mate > black > white > fennel. For total polyphenol content the order was: white > mint > black > matte > boldo > green > chamomile > carqueja > balm > fennel. The differences found in the samples from the same kind of tea can be attributed to the harvest season, soil type, planting location, climate differencesand from the parts of the vegetal material used in the preparation of the tea bags. CONCLUSION: All samples analyzed presented antioxidant activity and ability to scavenge H2O2. It was not possible to detect flavonoids, carotenes and catechins in only one sample.