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.

Assessment of the reducing capacity of processed fruit juices with the copper(I)/4,4'-dicarboxy-2,2'-biquinoline complexes.

An alternative method for quantification of the total reducing capacity (TRC) of processed ready-to-drink fruit juices (orange, grape, peach, mango, cashew, strawberry, apple and guava) is suggested. The spectrophotometric procedure is based on the reduction of Cu(II) to Cu(I) by antioxidants (present in the samples) in aqueous buffered solution (pH 7.0), containing 4,4'-dicarboxy-2,2'-biquinoline acid (H2BCA), yielding the [Formula: see text] complexes. The absorbance values at 558 nm (A558 nm) of the [Formula: see text] complexes obtained with juice samples were compared with A558 nm values of the same complexes obtained with a standard ascorbic acid solution and used to quantify and express the reducing capacity of each sample. Regarding orange juices a positive relationship between the TRC values using the [Formula: see text] complexes and the labelled ascorbic acid (AA) content along with the total polyphenol content (TPC) was measured. Grape juices showed the best positive correlation was verified between the TRC (with the [Formula: see text] complexes) and the TPC. While other fruit juices showed good agreement of TRC values with [Formula: see text] complexes and DPPH reagent. The proposed method may be applied to measure the TRC of beers and wines and also for biological samples like serum and follicular fluid.

Study of DNA damage caused by dipyrone in presence of some transition metal ions.

The DNA damage in the presence of dipyrone (used as its sodium salt, NaDip) and some transition metal ions in an air saturated ([O2] ≈ 0.25 mM) non-buffered solution at T = (25.0 ± 0.5)°C was investigated by agarose gel electrophoresis. As metal ions Cu2+, Fe3+, Ni2+ and Mn3+ were selected and evaluated in the present study because of the important role they play in a biological system. pUC19 plasmid DNA damage-induced by NaDip (80-600 µM) was observed in the presence of 100 µM Cu2+. The damage was proportional to the NaDip concentration provided that the order of addition of reagents (pUC19 plasmid DNA + Cu2+ + NaDip) is obeyed. Addition in the reaction medium of ligands for Cu2+ and Cu+, respectively EDTA and neocuproine, promoted total inhibition or reduction of the pUC19 plasmid DNA damage suggesting the involvement of the Cu2+/Cu+ cycle. Besides, the decrease in the pUC19 plasmid DNA damage after addition of catalase (1.0 × 10-4 mg µL-1) in the same reaction medium indicates that H2O2 is also involved in the damage process. In NaDip concentration range (80-600 µM), and under same the experimental conditions, it was not possible to conclude whether there was pUC19 plasmid DNA damage caused by 10 µM Fe3+. No damage was observed in the presence of Mn3+ or Ni2+. Although the technique used in this study is sensitive to detect the pUC19 plasmid DNA damage it was not possible to identify in which DNA base this damage occurs. Further studies with other techniques should be made to unambiguously identify the oxidative intermediates that are responsible for the DNA damage. As far as we know, this is the first study dealing with the pUC19 plasmid DNA damage-induced by NaDip in presence of copper, iron, nickel and manganese ions.

The evaluation of reduction of Fe(III) in 3-hydroxy-4-nitroso-2,7-naphthalene disulphonic medium as an alternative ferric reducing activity power assay.

INTRODUCTION: The growing interest in determination of anti-oxidant capacity through non-labour, effective and less costly methods encouraged the development of the spectrophotometric procedure presented in this study. OBJECTIVE: To investigate the reduction reaction of Fe(III) in 3-hydroxy-4-nitroso-2,7-naphthalenedisulphonic anion (NRS) medium as an alternative ferric reducing activity power (FRAP) assay for determining the total reduction capacity (RC). MATERIALS AND METHODS: The absorbance values at 730 nm were used to determine the RC of aqueous extracts of nine Brazilian plants. The results were compared with the values obtained with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and with the total polyphenol content (TPC). The RCs of phenolic derivatives, flavonoids, amino acids and other anti-oxidant compounds were determined. RESULTS: Paired t-test with RC values obtained with both assays (proposed FRAP and DPPH) showed no statistically significant difference. In addition, the RC values from the proposed FRAP assay are proportional to those found with TPC values (r =0.916). In addition, the conditional reduction potential of the Fe(III)/Fe(II) couple (0.685 V vs NHE (normal hydrogen electrode)) and the molar absorptivities at 730 nm of the Fe(NRS)(3)(3-) and Fe(NRS)(3)(4-) complexes (1.88 × 10(3) and 1.77 × 10(4) L/cm × mol, respectively) were calculated because these values were not available. CONCLUSION: The proposed assay is adequate for determination of the RC of plant extracts, and the results infer that other samples derived from plants (e.g. beers and wines) and even biological samples (e.g. serum and urine) also could be analysed.

Antioxidant Activity and Polyphenol Content of Some Brazilian Medicinal Plants Exploiting the Formation of the Fe(II)/2,2'-bipyridine Complexes.

Aqueous plant extracts contain polyphenols that reduce Fe3+ to Fe2+, which in the presence of excess 2,2'-bipyridine (bipy) yield the Fe(bipy)3(2+) complex (λmax = 521 nm). This reaction was used to quantify the total polyphenol content (TPC) of nineteen Brazilian medicinal species using pyrogallic acid (PA) as a standard. A calibration curve of absorbance values at 521 nm values vs. PA was linear from 0.378 to 3.03 mg L(-1) (r = 0.998; n = 8) with a limit of detection 0.16 mg L(-1). The TPC quantification using the proposed reaction was compared with values obtained with the Folin-Ciocalteu reagent, yielding good agreement (r = 0.965). For the same species the TPC obtained with the proposed method also resulted in good correlation (r = 0.773) with the antioxidant capacity values quantified using the 2,2-diphenyl-lI-picrylhydrazyl method. It was also found that Fe(bipy)3(2+) complexes can be used to calculate the reducing capability of polyphenols. The polyphenol structure, and the number and position of the hydroxyl group attached to the benzene ring modify this reductive capacity.

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.

A critical study of use of the Fe(II)/3-hydroxy-4-nitroso-2,7-naphthalenedisulfonic acid complexes in the quantification of polyphenols in medicinal plants.

A critical study of the use of the Fe(III)/3-hydroxy-4-nitroso-2,7-naphthalenedisulfonic acid (NRS) complexes on the quantification of the polyphenols content in aqueous extracts of plants, expressed as pyrogallic acid, [PA], is presented. The reaction used is based on the reduction of Fe(III) to Fe(II) by [PA] in the presence of NRS in a buffered medium (Tris; pH 8.0) with formation of Fe(II)/NRS complexes. A calibration curve of absorbance (at 730 nm) vs. [PA] is linear (r=0.998; n=7) from 1.0 to 7.0 µmolL(-1) [PA]. LD and RSD were 0.5 µmolL(-1) and 2.5% (6.0 µmolL(-1) [PA], n=10), respectively. The influence of pH, type of buffer solution and interfering species possibly present in the samples were evaluated. Aqueous extracts of twelve medicinal plants used in the Brazilian folk medicine were analysed by using both Fe(III)/NRS complexes and the Folin-Ciocalteu reagent.

Analysis of the polyphenols content in medicinal plants based on the reduction of Cu(II)/bicinchoninic complexes.

A spectrophotometric method is proposed for the determination of the polyphenols content in aqueous extracts of plants. The method is based on the reduction of Cu(II) to Cu(I) by polyphenols, in the presence of bicinchoninic acid in a buffered medium (ammonium acetate, pH 7.0) with the formation of Cu(I)/BCA complexes. A calibration curve of absorbance (at 558 nm) vs tannic acid concentration is linear (r = 0.995; n = 7) with tannic acid from 0.1 to 0.7 micromol L(-1). The limit of detection and relative standard deviation were 40 nmol L(-1) (99% confidence level) and 3.8% (0.4 micromol L(-1) tannic acid, n = 7), respectively. For the aqueous extracts of Hamamelis virginiana L., Maytenus ilicifolia Mart. ex Reissek, Hydrocotyle bonariensis Lam, Annona muricata L., Myrciaria cauliflora (Mart.) O. Berg., Caesearia sylvestris Sw., Schinus terebinthifolia (Raddi), and Stryphnodendron adstringens (Mart.) Coville, the total polyphenol contents, expressed as tannic acid, were 3.5, 1.3, 2.0, 3.1, 15.4, 3.1, 9.1, and 6.9%, respectively.