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     

Antioxidant Activity of Ripe and Unripe Pepino Fruit (Solanum muricatum Aiton)

Abstract: Ripe and unripe exotic pepino fruit were evaluated for antioxidant activity, total phenols, and flavonoid content. The antioxidant potency was investigated by employing various established in vitro systems, such as 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), 2–2′‐azinobis(3‐ethylbenthiazoline‐6‐sulphonic acid (ABTS), hydroxyl radical scavenging, reducing power, ferrous ion chelation, ferric reducing antioxidant power (FRAP), and lipid peroxidation. The EC₅₀ values of ripe ethanolic extract on DPPH radical, reducing power, ferrous ion chelation, ABTS radical, FRAP, hydroxyl radical, lipid peroxidation (brain), and lipid peroxidation (liver) were obtained to be 2.20, 2.81, <5.00, 34.06, 8.53, 1.30, 1.75, and 0.51 mg/mL, respectively. However, the EC₅₀ values for unripe fruit extract were noted to be 3.75, 3.40, 11.25, 40.12, 9.75, 0.80, 1.91, and 0.63 mg/mL, respectively. Ripe fruit exhibited the highest values of antioxidant activity in all the scavenging assays except for hydroxyl radical scavenging assay. Ripe pepino had higher total phenol and flavonoid content than unripe fruit. This study suggests that possible mechanism of the biological activities may be due to free radical scavenging and antioxidant characteristics, which may be due to the presence of polyphenols in the fruit extracts. Practical Application: The ripe and unripe pepino fruit have excellent antioxidant properties, so the results obtained in this study clearly indicate that pepino fruit has a significant potential to use as a natural antioxidant agent and possibly as a food supplement.     

Antioxidant activities of fresh grape juices prepared using various household processing methods

The purpose of this study was to evaluate and compare the antioxidant activities, and their contents, in grape juices prepared by various household juicers, and grape flesh (GF). The grape juices were prepared using a low-speed masticating (LSM) juicer, a high-speed centrifugal (HSC) juicer, and a blender (BLD). The total polyphenol, total flavonoid, total monomeric anthocyanin, and vitamin C contents were highest in the LSM grape juice, and decreased in the order: LSM > BLD > HSC > GF. The antioxidant activities such as DPPH radical scavenging activity, and SOD-like activity were significantly higher in the LSM juice than in other juices and grape flesh. The antioxidant activities and the quality of grape juices were significantly affected by the household juicing method used, and an LSM juicer is strongly recommended for making healthy grape juice, rich in antioxidants.     

Antioxidant activities of crude tea polyphenols, polysaccharides and proteins of selenium-enriched tea and regular green tea

The crude tea polyphenols, polysaccharides and proteins of regular green tea and Se-enriched green tea were investigated in vitro for antioxidant activities by auto-oxidation test (AAPH) and α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging method. Results showed that crude tea polyphenols of Se-enriched green tea provided the highest antioxidant activity by DPPH assay and the antioxidant activity was decreased in the order: crude tea polyphenols > crude tea proteins > tea polysaccharides. The crude protein of Se-enriched green tea was found to exhibit the highest antioxidant activity by AAPH method and the antioxidant activity was decreased in the order: crude tea proteins > tea polyphenols > tea polysaccharides. Tea polyphenols and tea polysaccharides of Se-enriched green tea presented significantly higher antioxidant activities than that of regular green tea. No significant difference of antioxidant activities was found between crude tea proteins of Se-enriched green tea and regular green tea. The combinations of Se with tea polyphenols and tea polysaccharides were responsible for the higher antioxidant activities of Se-enriched green tea than regular green tea.     

Correlation between antioxidant concentrations and activities of Yuja (Citrus junos Sieb ex Tanaka) and other citrus fruit

The antioxidant concentrations and activities of tangerines, yuja, lemons, and oranges in the Korean marketplace have been investigated. Flesh and peel tissues of the fruit were analyzed. The total vitamin C, total phenolics, flavonoid, hesperidin, and total antioxidant activity of all citrus types were higher in peel than flesh tissues. Total phenolic concentrations of flesh tissues were in the following order: lemon>yuja>tangerine>orange, while those concentrations in the peel were tangerine >yuja>orange>lemon. Lemon and yuja had higher hesperidin concentrations in flesh and peel tissues, respectively. Among the flesh samples, the total flavonoid and total phenolic concentrations were highly related with total antioxidant activity. The relationship between flavonoid and hesperidin was also strong among flesh and peel tissues. Our results indicate that citrus fruit includes high antioxidant compounds and activity and that citrus peel could be a good source of food ingredients.     

EFFECT OF STORAGE PERIOD AND EXPOSURE CONDITIONS ON THE QUALITY OF BOSANA EXTRA-VIRGIN OLIVE OIL

Changes in quality parameters, antioxidant compounds, oxidative stability and antioxidant activity during 18 months of storage of a monovarietal extra‐virgin olive oil from Bosana cultivar , and exposed to light and dark, were studied. Analysis of data showed that all the parameters underwent significant changes during storage: free acidity, peroxide and ultraviolet (UV) spectrophotometric indexes remained below the limits reported in the EEC Regulations 2568/91 and 1989/03 , and these are: ≤0.8% for acidity, ≤20 meq O₂/kg for peroxide and ≤2.50 and ≤0.22 for K232 and K270, respectively. Phenol andα‐tocopherol content decreased during storage (42.0 and 29.6%, respectively) while chlorophylls and carotenoids underwent a decrease until 8 months of storage (49% and 30%, respectively); after that, the values remained constant. Oxidative stability and antioxidant activity had not changed dramatically during 18 months. Phenols were significantly correlated to the antioxidant activity of the oil, while oxidative stability measured by Rancimat did not show any correlation with carotenoids, chlorophylls, phenols andα‐tocopherol. Regarding exposure conditions, storage in the dark was better in retaining the quality of the oil, as expected.     

Antioxidant Activities and Phenolic Compounds of Several Tissues of Pawpaw (Asimina triloba [L.] Dunal) Grown in Korea

Pawpaw (Asimina triloba [L.] Dunal) possesses antioxidant compounds and strong inhibitors of cancer cells, and is widely cultivated in North America, Canada, and Korea. We analyzed the total phenolic and total flavonoid contents (TPC and TFC, respectively) of pawpaw plants grown in Korea and the antioxidant activities of their roots, twigs, leaves, and fruit with respect to 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) radical scavenging activity, 2,2′‐azino‐bis diammonium salt (ABTS) radical scavenging activity, ferrous (Fe²⁺) chelating ability, and nitrite scavenging activity. Pearson's correlation analyses revealed a linear correlation between TPC and antioxidant activities (r² >0.69). Root methanol extracts had higher TPC and antioxidant activities than other extracts, which was also consistent with those from the phenolic compounds found in those extracts. Therefore, antioxidant activities seem to depend on the TPC of each pawpaw tissue and pawpaw roots might be useful as a natural source of natural antioxidants.     

Effects of antioxidants on peanut oil stability

Several antioxidants including phospholipids (PL), ascorbyl palmitate (AP), rosemary (ROS), tocopherol (TOC) and catechin (CAT) were chosen to study the effects on peanut oil stability. Among these antioxidants, catechin alone and composites of catechin with other antioxidants showed significant increases in oil stability as compared to control oil. A response surface design was used to study the effects of three antioxidant composites on the peanut oil stability. Results showed the OSI (Oxidation Stability Index) values are significantly influenced by CAT (p<0.0001), followed by ROS (p<0.05) and PL (p<0.5). TOC was the least significant (p>0.5) in the increase of OSI value. By considering cost, handling and minimum usage of antioxidants, the OSI value of peanut oil would reach 15–16 h by the addition of 1500 ppm of CAT and a maximum level of either 400 ppm of ROS or PL.     

Evaluation of antioxidant activities and phenolic subtype contents of ethanolic bran extracts of Thai pigmented rice varieties through chemical and cellular assays

This study revealed that the ethanolic bran extracts of 11 Thai pigmented (red and purple) and 2 nonpigmented rice varieties exerted scavenging activity against DPPH and ABTS radicals and ROS in HL‐60 cells in the following order: red > purple > nonpigmented rice. These rice extracts also showed the same order of phenolic and flavonoid contents, which were strongly correlated with their scavenging activity. Phenolic subtype analysis further indicated that proanthocyanidins as well as anthocyanins and protocatechuic acid contributed directly to antioxidant capacity in red and purple rice bran, respectively. In contrast, these pigmented rice bran extracts possessed moderate chelating activity partly attributed to their contents of phenolics and flavonoids, especially proanthocyanidins in red rice bran. Moreover, rice bran extracts significantly restored SOD and CAT activities in oxidative stress‐induced A549 cells. This study provides new insights on the intracellular potent antioxidant capacity of pigmented rice bran extracts in the cell‐based systems.     

Antioxidant Properties of Fresh,Powder, and Fiber Products of Mango (Mangifera Foetida) Fruit

This study was aimed to investigate the antioxidant capacity and antioxidant components in fresh, powder and fiber products prepared from Mangifera foetida fruit, locally known as bacang. The antioxidant capacity and components (reducing, flavonoid, carotenoid, and ascorbic acid contents) were in the order of fresh > fiber > powder, whereas based on β-carotene bleaching method, order of antioxidant activity was fiber > powder > fresh. Pearson correlation coefficient showed that there was positive and significant correlation (r > 0.9) between antioxidant capacity and certain antioxidant components.     

Antioxidants from a Chinese medicinal herb – Psoralea corylifolia L

The powder and extracts of Psoralea corylifolia L. were tested in lard at 100 °C by using the oxidative stability instrument (OSI) and were found to have strong antioxidant effects. Six compounds, bakuchiol, psoralen, isopsoralen, corylifolin, corylin and psoralidin were isolated from the herb and identified by UV, IR, Mass, ¹H and ¹³C NMR spectra and melting point. Their antioxidant activities were investigated individually and compared with butylated hydroxytoluene (BHT) and α-tocopherol by the OSI at 100 °C. The results showed that bakuchiol, corylifolin, corylin and psoralidin had strong antioxidant activities, and especially psoralidin (stronger antioxidant property than BHT), but psoralen and isopsoralen had no antioxidant activities at 0.02% and 0.04% levels. The antioxidant activities of the compounds decrease in the following order: Psoralidin > BHT > α-tocopherol > bakuchiol > corylifolin > corylin > isopsoralen ∼ psoralen.     

Evaluation of the antioxidant activity of Ruellia tuberosa

The antioxidant activity of Ruellia tuberosa L. (Acanthaceae) was investigated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay and the hydrogen peroxide-induced luminol chemiluminescence assay. The methanolic extract (ME) and its four fractions of water (WtF), ethyl acetate (EaF), chloroform (CfF), and n-hexane (HxF) were prepared and then subjected to antioxidant evaluation. The results of both methods revealed that R. tuberosa possesses potent antioxidant activity. The antioxidant activities of the different fractions tested decreased in the order of EaF > CfF > ME > WtF > HxF according to the hydrogen peroxide-induced luminol chemiluminescence assay, and results were the same with the exception of the rank order of HxF and WtF according to the DPPH free radical-scavenging assay. The results provide useful information on the pharmacological activities associated with free radicals of this traditional folk remedy.     

Phytochemical composition,cellular antioxidant capacity and antiproliferative activity in mango (Mangifera indica L.) pulp and peel

Cellular antioxidant activity (CAA) and inhibition of hepato‐cellular carcinoma (HepG2) proliferation were evaluated for the first time in the pulp and peel of mango cultivars. Comparatively, peel had high flavonoids and tocopherols content and showed significant antioxidant activity. Among all the studied cultivars, the Xiao Tainong peel was predominant with highest fistein, mangiferin and alpha‐tocopherol content and significant cellular antioxidant activity value 2986 ± 380 μmol QE/100 g FW. The HepG2 cells antiproliferation was maximum in the peel of Da Tainong and pulp of Aozhou with lowest EC₅₀ values, 2.35 ± 0.65 (peel) and 185.4 ± 10.9 (pulp) mg mL^?1, in a dose‐dependent manner. Negative associations of flavonoids and tocopherol compounds with CAA and antiproliferative activity in mango confirmed synergistic, additive or antagonistic actions of phytochemicals. The current study suggests that mango peel could be used as a value added ingredient or functional food and may contribute considerably to promote consumer health.     

Supercritical CO₂extraction of oleoresin from marigold (Tagetes erecta L.) flowers and determination of its antioxidant components with online HPLC-ABTS(·+) assay

BACKGROUND: Marigold is a traditional medicine herb which shows good pharmacological activity in many aspects. It is very important to obtain and investigate the specific bioactive compounds from marigold. The objective of the study was to extract the oleoresin from marigold with supercritical CO₂ (SC‐CO₂) at different pressures and temperatures, detect the fatty acid composition by gas chromatography–mass spectrometry and investigate the antioxidative components in the extracts by combined online high‐performance liquid chromatography‐2,2‐azinobis‐(3‐ethylbenzothiazolin‐6‐sulfonic acid (HPLC‐ABTS^?+) post‐column assay and HPLC‐tandem mass spectrometry. RESULTS: For the pressure range (20–40 MPa) and temperature range (30–70 °C), 30 MPa/70 °C gave the highest yield of oleoresin (58.9 g kg^?1). The dominant fatty acids of marigold flower oleoresin were linoleic acid (>26.41%), palmitic acid (>24.22%) and oleinic acid (>20.12%). Significant effects of the extraction pressure and temperature on the antioxidant activity were observed (P < 0.05). Lutein esters, α‐tocopherol, β‐tocopherol, γ‐tocopherol and δ‐tocopherol were the dominant antioxidant compounds in the extracts. CONCLUSION: The study has shown that the yield and total antioxidant activity of the marigold extracts were affected by the pressure and temperature of SC‐CO₂, and that online HPLC technique could be used as an efficient and rapid method for separation and identification of bioactive compounds from a complex mixture. Copyright © 2011 Society of Chemical Industry     

Optimization of Hull‐Less Pumpkin Seed Roasting Conditions Using Response Surface Methodology

Abstract: Response surface methodology (RSM) was applied to optimize hull‐less pumpkin seed roasting conditions before seed pressing to maximize the biochemical composition and antioxidant capacity of the virgin pumpkin oils obtained using a hydraulic press. Hull‐less pumpkin seeds were roasted for various lengths of time (30 to 70 min) at various roasting temperatures (90 to 130 °C), resulting in 9 different oil samples, while the responses were phospholipids content, total phenols content, α‐ and γ‐tocopherols, and antioxidative activity [by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free‐radical assay]. Mathematical models have shown that roasting conditions influenced all dependent variables at P < 0.05. The higher roasting temperatures had a significant effect (P < 0.05) on phospholipids, phenols, and α‐tocopherols contents, while longer roasting time had a significant effect (P < 0.05) on γ‐tocopherol content and antioxidant capacity, among the samples prepared under different roasting conditions. The optimum conditions for roasting the hull‐less pumpkin seeds were 120 °C for duration of 49 min, which resulted in these oil concentrations: phospholipids 0.29%, total phenols 23.06 mg/kg, α‐tocopherol 5.74 mg/100 g, γ‐tocopherol 24.41 mg/100 g, and an antioxidative activity (EC₅₀) of 27.18 mg oil/mg DPPH. Practical Application: A well‐defined roasting process is very important for the food industry to be able to produce pumpkin seed oil with desirable nutritive and chemical characteristics of this unique salad oil, which changes during the roasting. This study contributes to the knowledge of a product design process for the roasting conditions of naked pumpkin seeds based on results that have demonstrated that an increase in roasting temperature significantly increased the biochemical values and antioxidant properties of the obtained virgin oils.     

Contribution of major lipophilic antioxidants to the antioxidant activity of basil extracts: an EPR study

BACKGROUND: The present research analyses the contribution of some lipid antioxidants to the antioxidant activity of lipophilic extracts from basil by an electron paramagnetic resonance (EPR) study using the stable free radical 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH). DPPH assay is considered an easy and accurate method with regard to measuring the antioxidant activity of plant extracts and EPR has already been employed to determine antioxidant activities of lipophilic plant extracts. RESULTS: Lipid extracts were obtained from basil grown hydroponically for 20 or 35 days from sowing and in soil for 35 days from sowing. Fast and slow rate constants were distinguishable in the decay kinetics of DPPH mixture added with lipid extract. Antioxidants with kinetics characterized by a fast decay rate were tocopherols and chlorophylls, whereas those characterized by a slow decay rate were carotenoids, among which were β‐carotene, lutein, β‐apo‐8′‐carotenal and zeaxanthin. The 20‐day hydroponically grown sample, which showed higher contents of tocopherol, chlorophyll and carotenoid molecules, was the sample endowed with the higher content of fast lipophilic antioxidants (FLA) and slow lipophilic antioxidants (SLA). CONCLUSION: The three samples showed different compositions of FLA and SLA, giving rise to different decay kinetics. Despite the differences, in all samples tocopherol contributed about 0.3% to the bulk of FLA, whereas the figure for chlorophyll was about 40%, evidencing the relevant but little‐studied role of chlorophyll as an antioxidant. Copyright © 2011 Society of Chemical Industry     

Concentration‐dependent antioxidant activities of conjugated linoleic acid and α‐tocopherol in corn oil

BACKGROUND: Antioxidants prevent rancidity (lipid peroxidation) and natural antioxidants, e.g., α‐tocopherol, likely provide additional value to oil‐based food products because of their health benefits. Conjugated linoleic acid (CLA) has potential health benefits and may exhibit antioxidant properties. The main aim of this study was to compare the antioxidant efficacy of α‐tocopherol, trans‐10, cis‐12‐CLA and cis‐9, trans‐11‐CLA (in graded concentrations) added to antioxidant‐stripped corn oil. RESULTS: As compared to α‐tocopherol, both CLA isomers displayed significant inhibition of corn oil lipid peroxidation induced by copper. Inhibition of thiobarbituric acid reactive substances (TBARS) were CLA concentration dependent for both isomers but with significant inhibition occurring at 0.1 and 1 ppm of CLA isomers or α‐tocopherol, respectively (P < 0.05). Graded concentrations of α‐tocopherol, and for both CLA isomers and time, had significant effects on TBARS formation (P < 0.0001). There were significant effects in interactions between graded concentrations and time for both CLA isomers (P < 0.0001) but not for α‐tocopherol (P > 0.05). CONCLUSION: CLA compounds could serve as useful food antioxidants and provide additional value because of their potential bioactivity in disease prevention. Copyright © 2007 Society of Chemical Industry     

Cytoprotective effects of polyphenolics on H<Subscript>2</Subscript>O<Subscript>2</Subscript>-induced cell death in SH-SY5Y cells in relation to their antioxidant activities

The cytoprotective effects of five flavonoids (quercetin, rutin, catechin, kaempferol and morin) and four hydroxycinnamic acids (caffeic, ferulic, sinapic and chlorogenic acids) were evaluated by the degree of protection they provided against H₂O₂-induced damage to human neuroblastoma SH-SY5Y cells. All compounds exhibited protection against H₂O₂-mediated cytotoxicity in a dose dependent manner. The concentration required to give a 50% reduction in cell death (EC₅₀ value) were derived from their dose–response relationships. The cytoprotective activities of these phenolic compounds in the order of quercetin > caffeic acid > rutin > chlorogenic acid > catechin > ferulic acid > sinapic acid > morin > kaempferol. The EC₅₀ values of the phenolic compounds were strongly related to their chemical structures. The EC₅₀ values were compared with the antioxidant activities as determined by five different chemically based antioxidant assays [2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), ferric reducing antioxidant power (FRAP) and lipid peroxidation inhibition capacity (LPIC)]. The ability of these phenolic compounds to protect from H₂O₂-induced SH-SY5Y cell death correlated (r ² = 0.85) with their determined LPIC values and weakly (r ² = 0.44) with their ABTS activities. There was no correlation between EC₅₀ values and ORAC, FRAP or DPPH activities. The cytoprotection assay is a more biologically relevant measurement than the chemically defined antioxidant activity assays because it uses human cells as a substrate and therefore accounts for some aspects of uptake, metabolism and location of antioxidant compounds within cells.     

Phenolic composition and antioxidant activity of Thai and Eri silk sericins

The present study investigates the phenolic contents and antioxidant activities of silk sericin extracted (SSE) from Thai mulberry silkworms (Bombyx mori) and non-mulberry silkworm (Samia ricini). The SSE from all strains revealed the mainly presence of flavonoid compounds including (+)-catechin (20.63–145.64 mg/100 g), quercetin (7.89–35.95 mg/100 g), and (−)-epicatechin (3.36–44.19 mg/100 g). The antioxidant activity of the SSE with water from Chokumnoui 1 was found to have low EC50 values (0.96 mg/mL), the concentrations of the SSE that exhibit 50% reduction in DPPH, and highest scavenging of ABTS^{· +} radicals (1.73 mg TEAC/g) and highest reduce TPRZ-Fe (III) complex to TPTZ-Fe (II) (8.03 mg Fe(II)/g), thus indicating high antioxidant activities. Total phenolic content and total flavonoid content of the SSE showed positive correlated to the scavenging activity of DPPH and ABTS^{· +} radicals and the ferric reducing ability (FRAP assay).     

Mineral composition,antioxidant and cytotoxic biopotentials of wild‐growing Ganoderma species (Serbia): G. lucidum (Curtis) P. Karst vs. G. applanatum (Pers.) Pat.

The aim of this work was to analyse mineral composition and chemical profile of two nonedible fungal species: Ganoderma lucidum and Ganoderma applanatum (Fru?ka Gora, Serbia) vs. their antioxidant (ABTS and A.E.A.C. assay) and cytotoxic biopotentials (MTT assay on MCF‐7). Both species were analysed for their content of macro‐ and microelements by atomic absorption spectrophotometry, while phenolic profile of EtOH and H₂O extracts was examined by LC‐MS/MS technique. Both species mostly contained the following ions: K⁺ > Ca²⁺ > Mg²⁺ > Mn²⁺ > Zn²⁺ > Cu²⁺ > Cr³⁺. Among nine phenolic compounds, the highest content of vanillic acid was detected in G. applanatum extracts while protocatechuic acid in EtOH extract and quinic acid in H₂O extract were mostly contained in G. lucidum. Ganoderma applanatum EtOH extract showed the best antioxidant activities related to its phenolic and flavonoid content. Further, the best cytotoxic effect after 72 h was observed in this extract as well.