Hydrogen-donating Activity Research Articles

Investigation of the impact of copper nanoparticles coated with ocimum bassilicum at chemoradiotherapy of colon carcinoma

BackgroundColon carcinoma poses a significant health challenge globally, particularly in developed nations where sedentary lifestyles, poor dietary choices, and genetic factors play a crucial role in its prevalence. Chemotherapy, the primary treatment method, carries severe side effects that can jeopardize patients' lives. Herbal extracts such as Ocimum Basillicum extract have shown effectiveness against cancer cells. Additionally, nanoparticles can significantly enhance drug delivery efficacy in these scenarios. AimThis article aims to investigate the impact of copper nanoparticles coated with Ocimum Bassilicum at chemoradiotherapy of Colon Carcinoma to hopefully create new treatment options with fewer side effects for patients. MethodologyCuO bio-NPs were produced by the addition of 15 mL of extract dropwise to 80 mL of a 5 mM Cu (OAc)2 aqueous solution, which was then refluxed for 2 h at 100 °C. The mixture gradually became darker brown in color as a result of the heating procedure. The production of CuO NPs and the hydrogen-donating activity of antioxidant phenols within the plant are signaled by surface plasmon resonance excitation, which is the cause of this. In the cell culture, LS174t colon cancer cells were treated with OB extract, CuNPs, and OB-coated CuNPs with and without different radiation levels in order to assess cell viability, through the MTT assay, and the pro-apoptotic BAX and anti-apoptotic BCL2 expressions, through qPCR assay. ResultsThe results demonstrate a decrease in cell viability and the expression of BCL2 and an increase in the expression of BAX especially when treated with OB-coated CuNPs and even furthermore when paired with radiation therapy. ConclusionsAfter doing the clinical trial studies, the recent nanoparticles can be used for the treatment of Colorectal carcinoma.

The mechanism and rate constant of hydrogen transfer from solvent radicals to coal-based model compounds in direct coal liquefaction

In direct coal liquefaction, in addition to stabilizing coal radicals, the ability of solvent-derived cyclohexadienyl radicals to hydrolyze bridge bonds in coal is a part of their hydrogen-donating activity. In this work, the density functional theory calculations and transition state theory were employed quantitatively to analyze the rate constants of hydrogen transfer from solvent-derived cyclohexadienyl radicals to coal model compounds. Results indicated that polycyclic 9,10-dihydrophenanthrene, 4,5-dihydropyrene and 4,5,9,10-tetrahydropyrene radicals have higher hydrogenolysis ability, therefore they can promote the breakage of the Caryl–Calkyl bonds more effectively. There is no obvious correlation between the rate constants of hydrogen transfer from H-donors radicals to ipso-C of different coal model compounds and the dissociation enthalpies of Caryl–Calkyl bond. However, it can be found that model compounds with higher bond dissociation energies are more susceptible to hydrogenolysis by solvent-derived cyclohexadienyl radicals. Among the coal model compounds containing the same functional group, the coal model compounds with substituent groups directly attached to aromatic rings are more easily hydrolyzed by solvent-derived cyclohexadienyl radicals.

Rate constant of hydrogen transfer from H-donor solvents to coal radicals

To investigate the sustainability of direct coal liquefaction, evaluating the hydrogen-donating activity of hydrogen-donor solvents (H-donors) is one of the critical parameters to determining the distribution and quality of liquid fuels. However, it is difficult to assess the capability of H-donors through experiments alone. Therefore, in this work, the density functional theory calculations and transition state theory were employed quantitatively to analyze the rate constants of hydrogen transfer from H-donors to coal radicals. Results indicated that hyperconjugation and ring strain play essential roles in the hydrogen-donating activity of H-donors. The hydrogen-donating activity is enhanced when the methyl group is substituted at the α position of tetralin. With the increase of alkyl substituents’ chain length, the hydrogen-donating activity of 1-ethyltetralin, 1-propyltetralin, and 1-butyltetralin are close but lower than that of 1-methyltetralin. The alkyl isomerization has a significant influence on the hydrogen-donating activity of H-donors. Due to a higher ring strain, the hydrogen-donating activity of H-donors containing five-membered saturated rings is lower than that of the hydrogenated aromatics with similar structures. Experimental data from the literature confirm the theoretical analysis.

Catalytic hydrogenation of stearic acid over reduced NiMo catalysts: Structure–activity relationship and effect of the hydrogen-donor

Reduced NiMo catalysts were prepared by loading NiMo elements on a γ-Al2O3-β-zeolite composite support, followed by reduction with hydrogen at temperatures in the range of 400–600°C. The hydrogenation activities were investigated through treatment of stearic acid (SA), and were compared with those obtained with the composite support and the oxidized NiMo catalyst (Cox). In the tested reduction temperature range, the catalyst reduced at 450°C (T450) achieved the highest conversion (close to 100%) and C18 hydrocarbon selectivity (58.0%), which were much higher than the results obtained over the composite support and Cox. Reduction treatment contributed to production of more reducible metal species and improvement of the dispersity of metal active sites, consequently leading to high hydrodeoxygenation activity. Furthermore, the effects of H2 pressure and the hydrogen-donor (tetralin) on the catalytic activity of T450 were investigated. Higher H2 pressures promoted SA conversion and C18 selectivity. In contrast with dodecane as a solvent, tetralin significantly promoted the formation of C18 in a H2 atmosphere, but improved the production of C17 and suppressed the formation of lighter hydrocarbons (≤C16) in a N2 atmosphere. This is associated with the hydrogen-donating activity of tetralin.

Thermal treatment of FCC slurry oil under hydrogen: Correlation of hydrogen transfer ability with carbonization performance of the fractions

Hydrogen transfer property is of great importance in the carbonization of heavy oils. Thermal treatment under hydrogen was performed on a raw slurry oil (SO) from FCC process. The theoretical hydrogen-donating property of SO fractions before and after treatment was predicted by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. The hydrogen-transfer experiments using anthracene (ANT) and 9,10-dihydroanthracene (DHA) as chemical probes were carried out to determine the hydrogen transfer ability (HTA) of SO fractions, the effect of which was examined by subsequent carbonization experiments. Results show that the donatable hydrogen contents of SO fractions are increased after thermal treatment under hydrogen. A modified method for calculating the hydrogen-donating ability (HDA) of the fractions is proposed on the basis of the 1H NMR data of the reacted mixtures derived from the hydrogen-donating experiments. The results calculated with this method are more accurate with inherent ANTs and DHAs considered. The HDA is found to be closely related to the composition of hydroaromatics in terms of the content and hydrogen-donating activity. The hydrogen-accepting ability (HAA) of the fractions is also calculated with similar method proposed accordingly, and thus the hydrogen-donating index that quantitatively describes the HTA is obtained. Thermal treatment under hydrogen improves the HTA of the fractions considering the increased HDA and decreased HAA after treatment, and also improves the morphology of derived semi-cokes as indicated by subsequent carbonization experiments. The correlation between the HTA of SO fractions and the morphology of derived semi-cokes reveals that the quality of derived cokes improves as the HTA of carbonization feedstocks improves, not necessarily in positive correlation with the HDA of SO fractions nor necessarily in negative correlation with the HAA of SO fractions.

Antioxidant, Anti-alzheimer and Anti-parkinson activity of Artemisia nilagirica Leaves with Flowering Tops

Presently peoples are loaded with stress and leads to various neurodegenerative disorders like anxiety, Alzheimer’s disease and Parkinson’s disease. The present study was aimed to investigate the antioxidant, anti-alzheimer and anti-parkinson activity of Artemisia nilagirica leaves with flowering tops extracts. The ethanol and aqueous extracts of Artemisia nilagirica leaves with flowering tops were processed for evaluation of in vitro antioxidant activity namely hydrogen-donating activity, superoxide scavenging activity, total polyphenol content, total flavonol content and reducing power assay. The object recognition and Y-Maze test were used to evaluate the anti-alzheimer's activity of extract. The different parameters like catalepsy (bar test), locomotor activity (actophotometer test), and muscle activity (rotarod test) were measured in all animals for anti-parkinson activity. The findings of in vitro antioxidant study demonstrated that ethanol extract has maximum antioxidant properties compared to aqueous extract. Hence the ethanol extract of Artemisia nilagirica was selected for screening of anti-alzheimer and anti-parkinson activity. The administration of ethanol extract of Artemisia nilgirica exhibited significant anti-alzheimer and anti-parkinson activity. The findings of anti-alzheimer and anti-parkinson activity ethanol extract of Artemisia nilagirica demonstrated that this plant have neuroprotective properties.

Preliminary Phytochemical Screening and In vitro Antioxidant Activity of Nigella sativa and Allium cepa Oil

Many oxidative stress related diseases are as a consequence of accumulation of free radicals in the body. The various researches are going on globally directed towards finding natural antioxidants of plants origins. We planned to investigate the preliminary phytochemical screening and in vitro antioxidant activity of Nigella sativa and Allium cepa oil. The yield of oil of Nigella sativa and Allium cepa were 21.5% and 27.3%, respectively. Phytochemical screening was performed by using standard methods. The in vitro antioxidant study was done for Nigella sativa and Allium cepa oil by using hydrogen-donating activity, superoxide scavenging activity, hydrogen peroxide scavenging assay and reducing power assay. The result of phytochemical screening demonstrated the presence of flavonoids, steroids and fats in Nigella sativa and Allium cepa oil. The findings of DPPH, superoxide, reducing power and H2O2 radical scavenging activity exhibited that the oil of Nigella sativa and Allium cepa showed moderately to strongly free radical scavenging activity. Hence Nigella sativa and Allium cepa oil can play a major role in alleviating the number of oxidative stress by reducing the oxidative damage to cellular component caused by Reactive oxygen species (ROS).

Application of the Kinetic Triplets and Geometrical Characteristics of Thermal Analysis Curves in Identifying the Main Bioactive Compounds (BC) that Govern the Thermal and Thermo-Oxidative Degradation Mechanism of Aronia melanocarpa (Black Chokeberry)

Thermal and thermo-oxidative kinetics of Aronia melanocarpa fresh samples was investigated. The current investigation was based on the application of kinetic triplets and geometrical characteristics of thermal analysis curves in identifying the main bioactive compounds that govern the thermal and thermo-oxidative degradation mechanisms. From established kinetic model in an argon atmosphere, it was found that released products arise from decomposition of phenolic compounds where autocatalysis may occurs from the inevitable presence of water already in the early stages of the process through the hydrolysis reaction pathway. In the case of thermo-oxidative degradation, it was found that the main mechanistic scheme can be presented with two different forms of reaction mechanism function, such as: nth order reaction model (with n > 1) (in lower heating mode) and Sestak-Berggren autocatalytic model (in higher heating mode). Isoconversional analysis has been shown that neochlorogenic acid represents the governed bioactive compound which has a strong hydrogen-donating activity. Based on the mechanistic conclusions, it was established that in an air atmosphere, the cyanidin-3-glucosylrutinoside (Cy-3-GR) degradation significantly participates in overall complex mechanism.

Isoconversional kinetic study and accurate determination of lifetime properties for thermal and thermo-oxidative degradation processes of Aronia melanocarpa

Abstract Isoconversional analysis and accurate determination of lifetime properties for thermal and thermo-oxidative degradation processes of Aronia melanocarpa were examined. The Sestak–Berggren (SB) autocatalytic model was found as best model to describe degradation process of A. melanocarpa in inert atmosphere. It has been found that autocatalysis may occur from inevitable presence of water probably through the hydrolysis. In the case of thermo-oxidative degradation, it was found that main mechanistic scheme can be presented with two different forms of reaction mechanism function, such as n th-order reaction model (with n > 1) and SB autocatalytic model. It was determined that neochlorogenic acid represents main compound, which has a strong hydrogen-donating activity. Based on lifetime analysis, it was found that in oxidative conditions, A. melanocarpa shows greater resistance to temperature variations, which correspond to storage conditions and where degradation mechanism greatly affects stability and physico-chemical characteristics of its constituents. Industrial relevance Current research has a direct industrial application during the testing of “responses” of black chokeberry— A. melanocarpa fresh samples on the various thermal stresses in the inert and oxidative reaction conditions. Knowledge of the exact mechanism of degradation (referring to precisely defined reaction pathways) of A. melanocarpa in different reaction atmospheres enables us the targeting an exactly isolated chemical compounds in A. melanocarpa fresh samples, which are responsible for antioxidant protection of human tissue and plasma. The results presented in this paper can be guidelines for the application of industrial processes for precise allocations of these compounds and their further testing for the treatment of malignant diseases. The importance of this research also comes down to the fact that 25% of total polyphenols in chokeberry fruits are anthocyanins, which represent the powerful antioxidants in vitro. Also, the current work provides a specific approach in accurate determination of lifetime properties of A. melanocarpa samples, which is very important in terms of checking the behavior of tested fruit berry system on the temperature variations during storage periods.

Analysis of the isoflavone content, antioxidant activity, and SDS-PAGE of cheese analogs produced with different proteolysis and soymilk residue contents

We investigated the heat coagulation, SDS-PAGE, isoflavone content, and hydrogen-donating activity of cheese analogs produced with different hydrolysis time (0.3 % Flavourzyme® for 0, 20, 25, and 30 min) and soymilk residue contents (0, 7, 14, and 21 %) to improve the protein functionality and to use the by-product of soymilk. SDS gel electrophoresis of samples treated with Flavourzyme confirmed that the Flavourzyme treatments not only decreased the molecular weight of the proteins but also removed lipoxygenase, which results in the beany flavor of soy cheese, and Kunitz inhibitor (KTI), the antinutritional factor. The results of SDS-PAGE in the soy flour group and the roasted soy flour group treated with Flavourzyme® for 25 min and the determined soy milk residue contents indicated the recovery of some fractions (50, 32, and 18 kDa) of 7S and 11S globulin. The heat coagulation ratio increased as the amount of added soymilk residue was increased up to 14 % (p < 0.001). The glycoside (daidzin and genistin) and total isoflavone content increased in both the soy flour group and the roasted soy flour group as the amount of added soymilk residue was increased, but the contents of non-glycosidic compounds and the anti-oxidative activity were the highest in soy flour samples to which 7 % soymilk residue was added(p < 0.001). The variation in the anti-oxidative activity was similar to the variation in the contents of non-glycosidic compounds.

6년생 인삼(연풍)의 뿌리부위별 항산화 활성

The objective of this study was to evaluate the contents of reducing sugar and total polyphenol and the antioxidant activity of freeze-dried ginseng (Panax ginseng C.A. meyer cv Yun-poong). Ginseng root consists of the main root (MR), lateral root (LR) and fine root (FR). These roots were sorted into 3~4 groups (MR 1~4 groups, LR 1~4 groups, FR 1~3 groups) depending on the diameter of center region. The reducing sugar content has no influence on the diameter, but the reducing sugar content was decreased by subdivision. Total polyphenol contents of ginseng were the highest in FR-3 among all others. The antioxidant activity was measured using DPPH radical scavenging activity and ABTS radical scavenging activity. The (50% inhibitory concentration) value of the hydrogen donating activity was the highest in FR-3 as 7.03 mg/mL and the lowest in MR-2 as 37.02 mg/mL. Overall, hydrogen donating activity of FR was higher than the main root and lateral root significantly (p

Comparison of antioxidant activity from different root part of 6‐year‐old Panax ginseng C.A. meyer(Yun‐poong).

The objective of this study is to evaluation the total polyphenol and the antioxidant activity of freeze‐dried ginseng(Panax genseng C.A. meyer cv Yun‐poong) for root area and diameter. Ginseng root consists of the main root(MR), lateral root(LR) and fine root(FR). These roots were sorted 3~4 group(MR 1~4 group, LR 1~4 group, FR 1~3 group) depending on the diameter of each center region. Total polyphenol content of ginseng showed the highest in FR‐3 among the all samples. The antioxidant activity measured using DPPH radical‐scavenging activity and ABTS radical scavenging activity. DPPH radical‐scavenging activity of FR‐3(IC50: 7.03 mg/mL) showed the highest value in all samples but MR‐2(IC50: 37.02 mg/mL) showed the lowest value. On the whole, hydrogen donating activity of FR was significantly higher than for other groups. ABTS radical scavenging activity of FR‐3 was significantly higher than any of the other samples. Polyphenol content and antioxidant activity of ginseng showed the highest in FR‐3 and the result exhibited that polyphenol content and antioxidant activity of ginseng were related to root area and diameter.

산수유 에탄올 추출물의 생리활성

산수유를 기능성식품 소재로서 이용하기 위하여 산수유 에탄올추출물의 생리활성을 조사하였다. 산수유 에탄올추출물의 수소공여능은 농도 의존적으로 증가되었으며, 300 및 500 ㎍/mL 농도에서 각각 64, 73%의 활성을 나타내었다. 대식세포 RAW264.7에 산수유 에탄올추출물을 100, 300 및 500 ㎍/mL의 농도로 처리하였을 때 산수유추출물은 농도 의존적으로 NO(nitric oxide)의 생성을 유도하였다. 또한 산수유 에탄올추출물을 유방암세포에 다양한 농도로 처리하여 24, 48, 72시간 반응시킨 결과 농도 및 시간에 의존적으로 유방암세포의 증식을 억제하였으며, 500 ㎍/mL 농도로 72시간 처리 시 60% 이상의 높은 증식억제율을 보여주었다. 또한, MCF-7 유방암 세포에 bisphenol과 17β-estradiol과 같은 환경호르몬을 0.1 μM의 농도로 처리하였을 때 세포의 증식이 유도되었으며, 이 세포에 산수유 에탄올추출물을 농도별로 72시간 처리하였을 때 유방암 세포의 증식이 억제되었다. 따라서 본 연구결과는 산수유의 기능성식품 소재로서의 활용 가능성을 시사한다.

저선량 전자선 조사가 살구의 저장 중 품질특성에 미치는 영향

살구에 1, 2 kGy 전자선을 조사한 후 2주간 미생물학적, 물리적, 이화학적 특성의 변화를 통해 품질에 미치는 영향을 알아보았다. 미생물학적 변화에서는 호기성 미생물 및 효모, 곰팡이군의 수가 전자선 조사에 의해 감소하는 것으로 나타났고, 저장기간 동안에 그 수가 증가하였다. 기계적 경도 측정 결과에서는 전자선 조사 직후부터 조사구가 비조사구보다 경도가 낮은 것으로 나타났으며, 조사선량에 비례하여 감소하였다. 또한 관능검사에서도 조사구의 경도가 감소하는 것으로 나타났으며, 1 kGy 조사구의 전체적인 기호도는 영향을 받지 않는 것으로 나타났다. 색도 측정에서는 전자선 조사에 의해 lightness, redness가 감소하는 것으로 나타났고, 환원당 함량은 전자선 조사된 시료가 비조사구에 비해 함량이 높은 것으로 나타났다. 또한 유기산 함량에서는 전자선 2 kGy 조사구가 저장기간 중 변화를 나타내지 않았으며, 전자선 조사에 의해 살구의 pH, 총당, 수소공여능 그리고 vitamin C 함량은 거의 영향을 받지 않는 것으로 나타났다. 따라서 살구에 대한 저선량의 전자선 조사는 살구를 연화시켜 저장기간 연장 및 품질 개선에 대한 효과는 관찰되지 않았지만 미생물학적 안전성을 가져오며, 이화학적 품질을 유지시키는 것으로 나타났다.

감마선 조사가 살구의 미생물학적.이화학적 변화에 미치는 영향

살구의 저장ㆍ유통 과정에서 품질 특성 및 살구 식품산업에 적용할 수 있는 자료제공을 위한 연구의 일환으로 살구에 0.5～2 kGy로 감마선 조사를 실시하여 20℃에서 2주간 저장하면서 살구의 미생물학적 및 이화학적 품질 특성을 조사하였다. 살구의 호기성 세균과 효모, 곰팡이 변화는 조사량이 증가할수록 감소하여 미생물 증가를 억제시킴을 알 수 있었다. 색도변화와 경도변화에서는 조사구에서 값이 감소하였다. 총당, 환원당 함량은 감마선 조사에 의한 영향을 나타내지 않았으며 수소공여능은 저장기간이 지남에 따라 감소하였고 유기산 및 비타민 C 함량은 저장기간 지남에 따라 증가하였으나 감마선 조사에 의한 영향은 나타나지 않았다. 관능검사 결과 저장초기에는 조사구에서 높은 기호도를 보였으나 저장기간이 지남에 따라 기호도가 비조사구보다 감소하였다. 따라서 감마선 조사는 살구의 색도, 물리적 특성에 좋지 않은 영향을 끼치지만 항산화 성분 등에 영향을 주지 않으면서 미생물학적 안정성에 효과적으로 사용될 수 있을 것으로 사료된다.

Antioxidant activity of hot water extract from the fruit of the Doum palm, Hyphaene thebaica

A hot water extract from the fruit of Hyphaene thebaica was examined for its (i) hydrogen donating activity, (ii) Fe 2+-chelating activity, (iii) hydroxyl radical-scavenging activity, (iv) inhibition of substrate site-specific hydroxyl radical formation, (v) superoxide radical-scavenging activity, and (vi) reducing power. The total phenolic content of the fruit extract was also determined in order to quantitate antioxidant activity as gallic acid equivalent (GAE) per ml reaction. The total phenolic content of the Doum fruit is low, but the extract exhibited potent antioxidant activity in terms of GAE. The activities expressed as mmol pure compound equivalent per g GAE content of extract are: (i) 2.85 mmol ascorbic acid equivalent, (ii) 1.78 mmol ethylenediamine tetraacetic acid equivalent, (iii) 192 mmol gallic acid equivalent, (iv) 3.36 mmol gallic acid equivalent, (v) 1.78 mmol gallic acid equivalent and (vi) 3.93 mmol ascorbic acid equivalent. These values were of the same magnitude as antioxidant activity in black tea except for Fe 2+-chelating activity which was about 14 times more potent. The results show that the fruit of Hyphaene thebaica’s fruit is a source of potent antioxidants.

Effects of Chitosan and Lactic Acid on Enzymatic Activities and Bioactive Compounds during Germination of Black Rice

The effect of chitosan on enzymatic activities and on bioactive compounds was characterized during germination at 25℃ for 7 days to search for a method to produce a germinated black rice. The germination rate was reduced by the addition of lactate and chitosan. The rotting rate was greatly decreased by chitosan, suggesting that the addition of chitosan into a germination solution might be an effective method for controlling fungal contamination during the germination of cereals. The addition of 100 and 200 ppm chitosan increased α-amylase activity after 7 days by up to 152% and 197%, respectively. The activities of β-amylase and β-glucosidase were lower with 200 ppm chitosan than in distilled water and 100 ppm lactate. The amount of total soluble phenolics and total flavonoids decreased rapidly for four days and thereafter remained constant until the seventh day. The antioxidant activity of germinated black rice, in terms of hydrogen-donating activity, increased slowly and did not correspond to the changes of total soluble phenolics and total flavonoids. The amount of phytic acid was reduced by the addition of 200 ppm chitosan compared to distilled water, indicating that chitosan could be used as an elicitor for the increase of phytase activity during the germination of black rice.

In vitro analysis of the properties of Beiqishen tea

Objective Chinese Beiqishen tea was studied in an in vitro test system. Methods Phytochemical screening, trace element analysis, and the analysis of antioxidant properties were carried out. Characteristic constituents were determined by chromatographic (capillary gas chromatography and GCQ Ion Trap mass spectrometry) and spectrometric (ultraviolet and UV-VIS) methods. Element concentrations were determined by inductively coupled plasma optical emission spectrometry. Antioxidant capacity was studied by spectrophotometric and luminometric techniques using a Berthold Lumat 9501 luminometer. Hydrogen-donating activity, reducing power, and total scavenger capacity were measured. Results Total polyphenol content was 20.77 ± 0.52 g/100 g of drug; total flavonoid content was 0.485 ± 0.036 g/100 g of drug; and tannin content was 9.063 ± 0.782 g/100 g of drug. Caffeine content was 1.08 mg/100 g of drug. Essential oils were identified by gas chromatography: (+)-limonene (21%), p-cymene (1.7%), estragol (3.2%), β-ocimene (1.4%), and thymol (2.6%). Metallic ion analysis showed significantly high concentrations of Al, As, Ba, Cr, Cu, Fe, Mn, Ni, and Ti in the drug. Antioxidant and scavenger properties were identified as a function of concentration. Conclusions The tea infusion contained some non-desirable trace elements and caffeine in addition to polyphenols and tannins in high concentrations. Therefore, the consumption of this tea may involve risks.

Chlorogenic acid content and antioxidant properties of potato tubers as related to nitrogen fertilisation

The chlorogenic acid and the total polyphenol content were analysed in two different potato varieties (Kennebec, Agria) grown under five different nitrogen fertiliser rates (0, 75, 150, 225, 300 kg ha-1). Chlorogenic acid content ranged between 6.0-22.3 mg kg-1 fresh weight and was not influenced by fertiliser levels. The chlorogenic acid in potato tubers accounted for almost 90% of the total polyphenols. Free radical scavenging and antioxidant activities of the tubers were also analysed. Ethanolic extracts if the tubers showed marked hydrogen-donating activity in the experiment using 1,1-diphenyl-2-picrylhydrazyl (DPPH), they had reducing power as measured by the Fe(III)?Fe(II) reaction, but did not exhibit H2O2 scavenging activity assessed with a chemiluminescence method. Potato extracts showed significant, although weak Cu(II)-chelating activity and inhibited the autoxidation of linolenic acid as measured by the thiocyanate method. Chlorogenic acid containing extract of potato, can act as primary and secondary antioxidant in prevention of oxidative stress. The strong correlation between the antioxidant activity and the level of total pholyphenols suggests that the phenolic compounds are important antioxidant components of whole potato tubers. Variety had minimal, while nitrogen fertiliser rate had no effects on the levels of the studied characteristics.

Flavonoids quercetin, myricetin, kaemferol and (+)-catechin as antioxidants in methyl linoleate

The antioxidant effect of the flavonoids quercetin, myricetin, kaemferol, (+)-catechin and rutin on methyl linoleate oxidation was investigated. In addition, the synergistic effects of flavonoids and α-tocopherol were studied. Oxidation was monitored by conjugated diene measurement and by determining the formation of hydroperoxide isomers by HPLC. The antioxidant activity of flavonoids in non-polar methyl linoleate differ from that previously reported in water-containing systems, such as LDL and liposome systems. The activity of antioxidants (10–1000 μM) measured by hydroperoxide formation decreased in the order: myricetin>quercetin>α-tocopherol>(+)-catechin >kaemferol=rutin. The antioxidant activity of flavonoids increased as the number of phenolic hydroxyl groups increased. In addition to the number of hydroxyl groups, other structural features such as the 2,3 double bond in the C-ring and a glycoside moiety in the molecule had an effect on the antioxidant activity. Myricetin and rutin, especially had a synergistic effect with α-tocopherol. Myricetin, quercetin and rutin protected α-tocopherol from decomposition, myricetin being the most protective. The relative hydrogen-donating activity measured by the ratio of cis,trans- to trans,transhydroperoxide isomers formed during oxidation decreased in the order: α-tocopherol >myricetin>quercetin. Hydroperoxide isomeric distribution of the samples containing kaemferol or rutin did not differ from the control. Thus, although α-tocopherol was the most effective hydrogendonor, myricetin and quercetin were more effective antioxidants in inhibiting the hydroperoxide formation in methyl linoleate. © 1999 Society of Chemical Industry