DPPH Solution Research Articles

Evaluation of the medicinal properties of Cyrtocarpa procera Kunth fruit extracts.

BackgroundThe fruit of Cyrtocarpa procera is used to treat stomach diseases by people living in San Rafael, Coxcatlan, Puebla. This work investigated the antibacterial, antioxidant, cytotoxic and anti-inflammatory activities of the fruit produced by this species.MethodsMethanol extract was obtained by maceration. After obtaining the methanol extract (MeOH1), methanol subextract (MeOH2) and hexane (H) were obtained. The antibacterial activities of MeOH1, MeOH2 and H were evaluated through disc-diffusion. The quenching of free radicals was evaluated by decolorizing a methanolic DPPH solution. The cytotoxic activity of MeOH2 was evaluated by in vitro assay system of growth inhibition of human cervical carcinoma cell line (CasKi). The IL-1β and TNF-α were determined through ELISA in the supernatants of the macrophage cell line (RAW 264.7). The MeOH2 subextract was separated by column chromatography, seventy-three fractions were collected.ResultsThe Gram-positive and -negative bacteria examined were sensitive to MeOH1 and MeOH2; the MeOH2 was bactericidal toward Staphyloccocus aureus (MIC = 4 mg/mL) and Vibrio cholera (MIC = 4 mg/mL). The MeOH2 inhibited the DPPH radical (SC50 = 69.7 μg/mL), but a cytotoxicity assay revealed that the extract is not toxic according to the National Cancer Institute (LD50 = 22.03 μg/mL). The production of proinflammatory cytokines (IL- 1β and TNF- α) by LPS- stimulated macrophages was reduced after the treatments. The methanol extract contained various organic acids, such as citric acid, palmitic acid and α- linoleic acid.ConclusionsThe fruits of Cyrtocarpa procera are employed to treat ailments such as diarrhea, in this study were demonstrated some biological activities involved in a bacterial infection. This is the first research about of the medicinal properties of C. procera fruit.

Validated HPTLC fingerprinting and antioxidant activity evaluation of twenty-seven Romanian red wines

A high performance thin layer chromatographic method (HPTLC) for fingerprinting and for the antioxidant activity evaluation of twenty-seven Romanian red wines was developed in order to discriminate wines as a function of grape varieties, vintage years and wineries. The chromatographic analysis was performed on silica gel 60F254 HPTLC aluminum sheets using ethyl acetate:formic acid:acetic acid:water, 20:2:2:4 (v/v/v/v) as mobile phase. Detection was performed under visible and UV light before and after dipping the plates in NP/PEG solutions. The chromatographic fingerprinting method was validated for stability, specificity, precision and robustness according to the general validation procedure of qualitative HPTLC method. The obtained fingerprints are useful for quality control of wines allowing their differentiation according to grape varieties, vintage years and wineries. The antioxidant activity evaluation of wines was performed by digitally processing the images taken after the plate immersion in a methanolic solution of DPPH for 1s. The antioxidant activity increases in the order Fetească Neagră, Cabernet Sauvignon, and Merlot. The total measured areas indicate that the lowest antioxidant activity corresponds to Fetească Neagră-Serve Ceptura (FN-SC) 2007 wine (At = 30min=4865u.a.) and Merlot-Prince Mircea (M-PM) 2006 wine has the highest antioxidant activity (At = 30min=14463u.a.).

Effect of Topical Application of Hydro-Ethanolic Extract of Acacia nilotica Pods on Second-Degree Cutaneous Infected Burns

Acacia nilotica is a medicinal plant used traditionally in Togo to treat various diseases including burn wounds. The aim of this study was to evaluate experimentally Acacia nilotica burn wound healing effect.Cutaneous burn wounds were symmetrically caused on depilated areas of rat skin through contact with an aluminum bar (r = 10 mm), preheated at 80°C for 30 sec. Five groups of animal were constituted and each group contained 8 mice. Four groups of animal’s burn wounds were infected by Staphylococcus aureus. One group burn wound is uninfected and serves as negative control. Burn wounds were assessed by planimetry and histological parameters of healing. Twelve days after burn wound induction, wound contraction in the uninfected groups (negative control) was 19.9% for topical application against -2.43% for infected control. In the infected groups treated with extract, wound contraction was generally stimulates. Histological examination showed granulated tissue developing over the wounds treated with the extract of A. nilotica at 2.5% and 5% where the proliferation of fibroblasts and neo-blood vessels was very marked.In conclusion, A. nilotica pod contents tannin, flavonoids, alkaloids and protein reduces DPPH solution and significantly accelerates wound healing of burns, and this is the case even if wounds are infected with 109CFU/mL of S. aureus.

Comparison of the Ingredient Quantities, and Antioxidant and Anti-inflammatory Activities of Hwangryunhaedok Decoction Pharmacopuncture by Preparation Type

Objectives : The main aim of this study was to assess the comparative efficiency of two preparation types of Hwangryunhaedok decoction(HRHD-D) using distilled and mixed extraction by measuring the index components and indicators of antioxidant and anti-inflammatory effects. Methods : The antioxidant activity was assessed by comparing distilled and mixed extractions of HRHD-D using an ELISA reader. The anti-inflammatory effect was determined by measuring NO amounts in RAW 264.7 cells. The contents were analyzed with high performance liquid chromatography-diode array detector(HPLC-DAD). Results : The electron donating ability of mixed and distilled extractions obtained with 500 ppm DPPH(1,1-diphenyl-2-picrylhydrazyl assay) solution were 57.8 % and 4.2 %, respectively. The total phenolic content of mixed extraction was 6.9 times that of distilled extraction and total flavonoid content was 51.5 times higher. The anti-inflammatory effect was assessed by NO measurement, and was found to increase significantly dependent on concentration in all mixed extract concentrations(25, 50, 100, 200, 400 μg/mL), but the difference in distilled extraction by concentration was only significant at 200 and 400 μg/mL. The HPLC analysis results of mixed extract of HRHD-D showed detection of all four main active constituents of HRHD-D. However, they were not detected in the distilled extract of HRHD-D. Conclusions : Mixed extraction with distillation added to decoction of HRHD-D showed better efficacy in antioxidant and anti-inflammatory effects, and ingredient quantities compared to distilled extraction. Further stability and clinical efficacy studies for standardization of mixed extractions are required.

Analyzing the phytochemical composition of Justicia neesii Ramam)

Phytochemical profile is an important aspect as it will give an over view of possible pharmacological properties of the plant. Justicia neesii is a plant belongs to Acanthaceae family, on which no significant phytochemical and pharmacological was done. The objective of the present study is to elucidate the phytochemical profile and analysis of antioxidant properties by TLC method. The phytochemical analysis was done for screening the maximum number of phytochemicals using standard methods. The TLC plates were developed with a solvent system containing methanol: chloroform: hexane at a ratio of 7:2:1. Ascorbic acid was used as positive control and a blank TLC plate was used as negative control in the experiment. The diluted DPPH in methanol was sprayed on the developed plates and observed under UV light. The preliminary phytochemical analysis shows the presence of flavonoids, glycosides, lactones, lignins, phenols, phytosterols, quinins, reducing sugars, saponins and terpinoids. The TLC analysis has shown the higher intensity of yellow color for the test spots which indicating the higher antioxidant potential of plant extract compared to standard ascorbic acid after treatment with DPPH solution. The plant is having good antioxidant potential. The plant was also composed of many significant phytochemicals.

Application of micro-TLC to the total antioxidant potential (TAP) measurement

DPPH is commonly applied for estimation of antioxidant capacity of single and complex biological samples, and changes colour from purple to yellow during reduction to DPPH-H. Importantly, for some samples, for example coloured foods, such reaction cannot be used because of interference from pigments. Therefore, the number of reported quantitative protocols involving off- or on-line sample reaction with DPPH are based on chromatographic separation of target components. In typical planar chromatographic assay, developed plates are sprayed with DPPH solution for antioxidant screening. Such approach enables simple visualisation of separated spots exhibiting antioxidant activities, but unfortunately, such procedure may also give the misleading signal for coloured spots. In the present communication we examined a new approach for measuring antioxidant capacity using quantitative analysis of DPPH and DPPH-H molecules after reaction with the sample, and then separated from the interfering compounds by micro-thin-layer chromatography. Particularly, the antioxidant capacities of coloured food samples (such as herbs and meads) were determined and the results compared with those obtained using the classical photometric assay. The main advantages of the new micro-TLC assay are (i) low cost, (ii) multiple measurements, (iii) short analysis time, (iv) simplification of sample preparation and (v) effective separation of DPPH signal from interfering compounds.

Effect of ambient temperature storage on 2,2-diphenyl-1-picrylhydrazyl (DPPH) as a free radical for the evaluation of antioxidant activity

Antioxidants are molecules involved in defense mechanisms against the deleterious effects of free radicals in most organisms. A number of methods are currently being used for the evaluation of the antioxidantand free-radical scavenging properties of natural and synthetic antioxidants, including the DPPH method. Numerous speculations about the stability of DPPH solution over a long period of time, at normal ambient temperature have been observed in previous studies but no definite information exists in literature in this regard. Using established protocols, the free-radical capability of DPPH methanolic solution (stored in dark at ambient temperature) was assessed using ascorbic acid as the antioxidant. Results revealed that DPPH methanolic solution gave comparable free-radical activity 24 hours post preparation compared with the freshly prepared solution. After 24 hours, activity was greatly reduced. We therefore recommend that freshly prepared DPPH solution should be used at all times; however for prolonged experimental schedules, the DPPH solution should be used within 24 hours post preparation, so as to give comparable results with the freshly prepared solution and avoid ambiguity in results interpretation.Keywords: Ascorbic acid, methanolic, oxygen species, phytochemicals, stability.

The activity-integrated method for quality assessment of reduning injection by on-line DPPH-CE-DAD.

A sensitive on-line DPPH-CE-DAD method was developed and validated for both screening and determining the concentration of seven antioxidants of Reduning injection. The pH and concentrations of buffer solution, SDS, β-CD and organic modifier were studied for the detection of DPPH and seven antioxidants. By on-line mixing DPPH and sample solution, a DPPH-CE method for testing the antioxidant activity of the complex matrix was successfully established and used to screen the antioxidant components of Reduning injection. Then, antioxidant components including caffeic acid, isochlorogenic acid A, isochlorogenic acid B, isochlorogenic acid C, chlorogenic acid, neochlorogenic acid and cryptochlorogenic acid were quantified by the newly established CE–DAD method. Finally, the total antioxidant activity and the multiple active components were selected as markers to evaluate the quality of Reduning injection. The results demonstrated that the on-line DPPH-CE-DAD method was reagent-saving, rapid and feasible for on-line simultaneous determination of total pharmacological activity and contents of multi-components samples. It was also a powerful method for evaluating the quality control and mechanism of action of TCM injection.

A thermodynamic in vitro antioxidant study of vitamins B (niacin and niacin amide) and C (ascorbic acid) with DPPH through UV spectrophotometric and physicochemical methods

A thermodynamically radical scavenging activity (RSA) of vitamin B niacin (NCN), niacin amide (NMD) and vitamin C ascorbic acid (AA) using 1,1-diphenyl-2-picrylhydrazyl (DPPH) through spectrophotometric and physicochemical methods at T=(298.15, 303.15 and 308.15) K has been studied. New experimental data on density, sound velocity, isentropic and apparent molal compressibility of vitamin+DPPH solutions are reported as a function of temperature and concentration. The results are discussed with regards to their structure–activity relationship (SAR) principles and relative deviations in RSAs with the structural potentials of the vitamins have been analyzed by comparing both the spectrophotometric and physicochemical results.

A Comparative Study on Antioxidant Potentials of Some Leafy Vegetables Consumed Widely in India

The antioxidant activities with respect to the 2,2-diphenyl-1-picrylhydrazyl (DPPH)-radical scavenging activity and reducing activity were assessed and compared for seven edible leafy vegetables (Enhydra fluctuans, Glinus oppositifolius, Amaranthus sp.1, Amaranthus sp.2, Amaranthus spinosus, Ipomoea aquatica and Corchorus sp.) widely consumed in India, especially West Bengal state. Phytochemical analysis of these vegetables revealed the presence of phenolics (gallic acid equivalents 2.87–61.85 mg/g), flavonoids (quercetin equivalents 2.75–406.98 mg/g) and tannins (tannic acid equivalents 7.39–32.52 mg/g). Two of the samples, E. fluctuans and Corchorus sp. exhibited remarkable DPPH radical scavenging activities (>70%) with significant IC50 values of 65.04 and 128.95 μg/mL, respectively. Extracts of these two species were also found to possess significant Fe3+-reducing activities. The constituents of the extracts were separated by thin layer chromatography (TLC) and the positions of the antioxidative active fractions were determined using TLC bioautography followed by spraying with DPPH solution. The study suggested E. fluctuans and Corchorus sp. to be potential sources of antioxidative compounds. Practical Applications Concerns regarding the use of synthetic antioxidants as preservatives in the food industry, because of their toxicity and harmful health hazards, have resulted in the limitation of their usage in the food industry. This has necessitated urgent search for novel antioxidative compounds of natural origin for use as food supplements as well as preservatives in the food industry. Many of the fruits and vegetables consumed daily possess significant antioxidant activities and are good sources of natural antioxidative compounds. The selected seven leafy vegetables, all of which are widely consumed in India, were studied with respect to their relative antioxidative potentials. Accordingly, E. fluctuans followed by Corchorus sp. were found to have the best potential as sources of natural antioxidative compounds for uses in nutraceutical and food industry.

Antioxidant Properties of Flavonoids and Honeys Studied By Optical Spectroscopy Methods

Flavonoids are considered very efficient radical scavengers and found in almost every plant. Antioxidant activities of flavonoids and a few popular kinds of bee honeys were investigated using absorbance spectroscopy. Spectral methods are powerful tools for the study of biologically active compounds and allow measurements of low concentrated substances under physiological conditions. Quercetin, naringenin, catechin, 3-hydroxyflavone were studied during the reaction with the 2,2-diphenyl-1- picrylhydrazyl radical (DPPH·). The results suggest that quercetin and catechin are better antioxidants than vitamin C. Among the analyzed honeys buckwheat honey exhibited the strongest antioxidant properties. Kinetic studies of the radical-scavenging activity were also performed. One can observe that popular vitamin C reduces free radicals instantly after adding to the solution, while flavonoids cause rather an exponential decay in concentration of the free radicals in the solutions. Our results show that adding of CuCl 2 to the solution of DPPH and quercetin did not influence the level of antioxidant capacity of quercetin.

Free radical scavenging activity and active metabolite profiling of endophytic fungi from Nothapodytes foetida and Hypericum mysorense

Abstract Background Chemical diversity of endophytic fungi has made them an alternate source for bioactive compounds. Novel biotopes with promising bioactivity are expected from endophytes of medicinal plants from biodiversity hotspots. Therefore, endophytes of Nothapodytes foetida and Hypericum mysorense from Western Ghats, India were screened for free radical scavenging activity and anti-radical metabolites were profiled. Methods Endophytes were isolated from surface sterilized leaves, stems and barks of N. foetida and H. mysorense . Ethyl acetate extracts of culture filtrates were tested for antiradical activity using DPPH and ABTS free radicals. Antiradical spots on developed chromatogram were profiled by spraying with DPPH solution. Results A dose dependent antiradical activity of variable magnitude was observed. Fourteen isolates from H. mysorense and thirteen isolates from N. foetida showed significant antiradical activity. 55% of tested isolates exhibited more than 95% quenching of DPPH radicals and 40% recorded more than 75% scavenging activity. A total of 66.67% of the tested isolates recorded more than 95% scavenging of ABTS radicals and 29.6% showed more than 75% scavenging activity. TLC of active extracts showed the presence of a minimum three and maximum thirteen radical scavenging metabolite spots. Conclusion This is the first report on antiradical activity of endophytic isolates of H. mysorense . Active metabolite profiling would help in the further purification of most potent and abundant bioactive molecule from the fungal endophytic extracts. Further purification and characterization of the active metabolites may lead to the discovery of novel bioactive molecules of industrial and pharmaceutical importance.

In vitro free radical scavenging activity of Jatropha gossgypifolia Linn. containing phenolic compounds

To evaluate the in vitro free radical (FR) scavenging activity of leaves Jatropha gossypifoliaLinn. petroleum ether, ethanol, aqueous extracts of J. gossypifolia were prepared, with successive extraction in Soxhlet apparatus. Each extract was selected to study the FR scavenging activity by superoxide scavenging assay and 2, 2-diphenyl-1 picrylhydrazyl hydrate (DPPH) radical scavenging assay method. It was found that aqueous extract contained carbohydrates, glycosides amino acids flavonoids, tannins, alkaloids and steroids; ethanolic extract contained glycosides amino acids flavonoids, tannins, alkaloids and steroids. Radical scavenging activity of plant extracts against stable DPPH was determined spectrophotometrically. Extract solutions were prepared by dissolving 0.025 g of dry extract in 10 ml of methanol. The solution of DPPH in methanol was prepared daily. The samples were kept in the dark for 15 min at room temperature and then the decrease in absorption was measured. Ethanolic extract of J. gossypifolia showed 58.7 ± 0.62% inhibition in superoxide scavenging model. Aqueous extract also showed almost similar activity (54.9 ± 0.53% compared to ethanolic extract), while petroleum ether extract showed poor inhibition of superoxide scavenging activity. All extracts showed dose and time dependent inhibition of superoxide scavenging activity. J. gossypifolia had the highest total phenolic content (42.60 mg tannic acid equivalent (TAE) /100 g fresh weight). Total phenolic content had positive correlation with antioxidant capacity. This shows that the plants, especially J. gossypifolia, may be potent source of natural antioxidants. Key words: Jatropha gossypifolia, 2, 2-diphenyl-1 picrylhydrazyl hydrate (DPPH), phenolic content, superoxide scavenging, antioxidant activity.

The study of Analgesic, Antidiarrhoeal and Anti-oxidant Effect of Ethanolic Extracts of Ecbolium linnaenum in Albino Mice

The Ecbolium linnaenum(leaves) is used as a folk medicine in Bangladesh for pain, diarrhea and infectious diseases. Phytochemical evaluation of the ethanolic extracts of Ecboliumlinnaenumleaves demonstratesthese pharmacologic effect for the presence of alkaloids, tannins, gums,flavonoids and absence of carbohydrates, steroids, saponins. In this present study an attempt was made to determine the analgesic, antidiarrhoel, antioxidantand antimicrobial effectin Swiss Albino mice. Ethanolic extracts of250 and 500 mg/kg showed significant inhibition of writhing reflex 36.20% (P< 0.01) and 54.48% (P< 0.001), respectively while the standard drug diclofenac-Na was 75.52% (P< 0.001) at a dose of 25 mg/kg body weight.In the castor oil-induced diarrhoealmice, the ethanolic extracts of 250 mg/kg & 500 mg/kg, raised the latent period and reduced the number of stools comparing with standard drug Loperamide. 0.02% DPPH solution of ethanol on TLC plate showed the presence of anti-oxidant components in the Ecboliumlinnaenum.From the % inhibition of ascorbic acid and Ecboliumlinnaenum we observe that it has anti-oxidation effect. The IC50 (inhibitory conc. 50%) for ascorbic acid is approximately 1 g/ml and for the sample it is more than 500 g/ml. The ethanolic extract of Ecboliumlinnaenum was tested for antimicrobial activity against a number of both gram positive and gram-negative bacteria but it does not show any anti-microbial effect.

DPPH Scavenging Assay of Eighty Four Bangladeshi Medicinal Plants

This study was designed to screen out free radical scavenging potentiality of 84 medicinal plants. Stock solution of different plant extracts and standard were diluted to achieve suitable concentrations. A control was also prepared without plant extract solution. Then 0.004% DPPH solution was added. The mixtures were incubated in the room temperature for 30 minutes. Then the absorbance was measured at 517 nm against solvent in UV-spectrophotometer and then IC50 was calculated. In this experiment two standard were used- ascorbic acid and BHT. Both showed a significant IC50 value of 15.5µg/mL, and 46.54µg/mL respectively. Among 84 medicinal plants Syzygim cumini, Casuarina littorea, Borassus flabellifer, Enhydra fluctuans, and Minusops elengi exhibited highest radical scavenging potential with an IC50 value of 12.816µg/mL, 14.467µg/mL, 15.755µg/mL, 15.653µg/mL, and 20.380µg/mL respectively. All these value are very close to the IC50 value of ascorbic acid and better than IC50 value of BHT (Butylated Hydroxy Toluene). Syzygim cumini is the most powerful scavenger among all tested medicinal plants and also most strong scavenger than ascorbic acid and BHT. Scavenging activity was found to increase in dose dependent manner. Another 30 medicinal plants exhibited good scavenging property and 14 medicinal plants showed moderate scavenging activity. The rest presented lower scavenging activity. This present study indicates that plants having good scavenging property may have various health beneficial effects and these plants can be considered as valuable source of bioactive components with high antioxidant properties.

비파 잎의 추출용매별 항산화성 검증과 활성물질의 분리 및 동정

To investigate potential medicinal or functional uses of Eriobotrya japonica, this study focused on the isolation and identification of antioxidant compounds from Eriobotrya japonica leaves. Various solvents were extracted from the leaves, and their scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals was measured, in addition to their superoxide dismutase-like activity, polyphenol compounds, and flavonoid content. Ethyl acetate extract exhibited the strongest scavenging effect in a 0.2 mM solution of DPPH (63.24±2.20%, 81.83±2.10%, and 93.15±2.31% in 0.3, 0.7, and 1.0 mg/ml sample concentrations, respectively). The antioxidant effect of the ethyl acetate extract and methanol extract were generally stronger than that of n-hexane extract. The extracts were further purified by repeated silica gel column chromatography. The antioxidant compounds were identified as phytol, β-sitosterol, and (-)-loliolide using GC/MS.

Identification of the Anti‐oxidants in Flos Chrysanthemi by HPLC–DAD–ESI/MSn and HPLC Coupled with a Post‐column Derivatisation System

Flos Chrysanthemi (Jiju) is a traditional Chinese medicine (TCM) that is known to have anti-oxidant activity; in this study, on-line HPLC-DAD-ESI/MS(n) and HPLC-DAD-DPPH methods have been developed for rapidly screening and identifying free-radical scavengers in Jiju extract. To develop an efficient method for the simultaneous identification and detection of the anti-oxidant components in Flos Chrysanthemi (Jiju). A concentrated methanol extract of Flos Chrysanthemi from Jiaxiang County (Jiju) was first separated into phases soluble in water, petroleum ether and n-butanol. The off-line 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging method was then used to evaluate the anti-oxidant activity of each phase in vitro. The results showed that the n-butanol extract had the highest anti-oxidant activity, and its anti-oxidant compounds were analysed by HPLC-DAD-ESI/MS(n) and HPLC coupled with a post-column derivatisation (PCD) system supplied with DPPH, aluminium chloride or sodium acetate solutions. A total of 17 compounds were separated and identified, three of which were identified in Jiju for the first time, and seven active compounds serve as the chemical basis of the anti-oxidant efficacy of Jiju. The methods described here allow rapid separation and convenient identification of the multiple constituents in Jiju, and may be applied to other complex natural matrices.

HIGH CAPACITY COUNTER CURRENT CHROMATOGRAPHY FOR THE ISOLATION OF ACTIVE INGREDIENTS FROM MEDICINAL PLANTS

s. PHYTOPHARM 2012 M 60 Obzory po kliniceskoj farmacologii i lekarstvennoj terapii [Reviews of clinical pharmacology and drug therapy] ТОМ 10/2012/2 Schisandrols A and b, schisantherin A, schisandrins A and b were detected in Schisandra oil extract by hPTlC (fig. 1A). These lignans are considered to be the main active substances of Schizandra chinensis. lignans antioxidant activity plays a significant role in pharmacological activity of Schizandra drugs (3). We established that these lignans don’t have fRSA by dPPh. They don’t bleach background of the plate after dPPh solution derivatization (fig. 1b). fRSA of Schizandra oil extract depend on other components of the extract, but not lignans. Thus, Schizandra oil extract is a source not only of the well-known lignans, but of other active compounds with the fRSA. The fRSA of these substances causes of their pharmacological importance.

Simple flow injection for screening of total antioxidant capacity by amperometric detection of DPPH radical on carbon nanotube modified-glassy carbon electrode

An amperometric flow injection (FI) method suitable for evaluation of ‘total antioxidant capacity’ (TAC) is presented. In this method, a carrier stream of a solution of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) continuously flows through an electrochemical cell, furnished with a carbon nanotube modified-glassy carbon electrode (CNT/GC) as the working electrode. At the applied voltage of 0.05V (vs. Ag/AgCl), DPPH• is reduced resulting in a constant electric current. For measurement of the TAC, a sample zone containing antioxidant(s) is injected into the carrier stream therein reduction reaction of DPPH• occurring within the sample zone. The decreased amount of the radical in the sample zone leads to a drop of the amperometric signal at the CNT/GC electrode. We have also compared the performance of the CNT/GC electrode to the unmodified GC electrode using cyclic voltammetry. The sensitivity of the CNT/GC electrode was more than twenty five times greater than the bare GC electrode. The study of the sweep rate dependence showed that the cathodic and anodic current of 0.1mM DPPH solution varied linearly (r2=0.998) with the square root of the scan rate, from 0.02 to 0.12Vs−1. These results demonstrated that the CNT/GC electrode is appropriate for the quantitation of antioxidants via amperometric detection of the residual concentration of non-reacted DPPH•. We obtained linear calibrations for all the antioxidants tested including gallic acid, catechin, quercetin, caffeic acid and Trolox. The system offers rapid sample throughput (45samplesh−1) and good precision of 3.2% R.S.D., for 20μL-injection of 2.5μM Trolox (n=30). This method was applied to evaluate the TAC of extracts of some Thai indigenous vegetables.

An Esr Study of Free Radicals Scavenging by Red Tea

An Esr Study of Free Radicals Scavenging by Red Tea Herbal tea is known to exhibit the scavenging of free radicals responsible for cellular damage. We studied the effect of water treated with reverse osmotic filter equipped with a special dielectric ceramic composite on the antioxidant activity of red tea. Methanol solution of DPPH was added to the tea extract and the RT decay of DPPH free radicals was studied by ESR spectroscopy. Red tea brewed from tap water treated with the composite filter was found to exhibit higher radical scavenging efficiency in comparison with that of the tea brewed from tap water, mineral water and reverse osmosis water.