Special Issue "Natural Products as Antioxidants"

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A special issue of Antioxidants (ISSN 2076-3921).

Deadline for manuscript submissions: closed (31 October 2014)

Special Issue Editors

Guest Editor
Dr. Maria G. Miguel

Universidade do Algarve, IBB-Centro de Biotecnologia Vegetal, Faculdade de Ciências e Tecnologia, Edif. 8, Campus de Gambelas, 8005-139 Faro, Portugal
Phone: +351289800900
Interests: In vitro antioxidant activity; in vivo antioxidant activity; phenols; terpenes; anti-inflammatory activity; free radicals; ageing; healthy eating
Guest Editor
Prof. Dr. João Rocha

Pharmacology and Translational Research Group (iMed.UL–FFUL), Faculty of Pharmacy, University of Lisbon, Lisboa 1649-003, Portugal
Phone: +351 217946400
Interests: Pharmacology of Local and Systemic Inflammation; Immunopharmacology; Lung Injury; Herbal Medicines and Functional Foods

Special Issue Information

Dear Colleagues,

Natural products have played an important role in the discovery of new drugs and innovative mechanisms of action. Among the various mechanisms exhibited by substances originating from natural products, antioxidant effects have been one of the most studied and pursued mechanisms. Given the importance of oxidative stress and the deleterious effects of reactive oxygen species in several diseases, it is very important to study molecules that are able to prevent or reduce the magnitude of these oxidative mediators. One of the main consequences or/and precursors of an oxidative process is inflammation. An inflammatory process can either initiate or be a consequence of cellular oxidative stress. Given the association of inflammation with several diseases (e.g., diabetes, neurodegenerative diseases, stroke, respiratory diseases and even cancer) the oxidative process is a potentially useful pharmacological target for many pathological conditions.
This issue invites researchers to contribute to original research articles as well as review articles related to the isolation, identification, and pharmacological characterization (pharmacokinetically and pharmacodynamically) of marine or plant natural products that exhibit antioxidant mechanisms with relevance as potential pharmacological targets.

Dr. Maria G. Miguel,
Prof. Dr. João Rocha
Guest Editors

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Antioxidants is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 300 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.


Keywords

  • antioxidant
  • inflammation
  • anti-inflammatory
  • pharmacology
  • natural products
  • functional foods
  • plant
  • marine

Published Papers (10 papers)

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Research

Open AccessArticle The Effect of Convolvulus arvensis Dried Extract as a Potential Antioxidant in Food Models
Antioxidants 2015, 4(1), 170-184; doi:10.3390/antiox4010170
Received: 31 October 2014 / Revised: 11 December 2014 / Accepted: 25 February 2015 / Published: 10 March 2015
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Abstract
In this study, the antioxidant activity of the Convolvulus arvensis Linn (CA) ethanol extract has been evaluated by different ways. The antioxidant activity of the extract assessed by 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation, the oxygen radical absorbance capacity (ORAC) and the ferric [...] Read more.
In this study, the antioxidant activity of the Convolvulus arvensis Linn (CA) ethanol extract has been evaluated by different ways. The antioxidant activity of the extract assessed by 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation, the oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP) was 1.62 mmol Trolox equivalents (TE)/g DW, 1.71 mmol TE/g DW and 2.11 mmol TE/g DW, respectively. CA ethanol extract exhibited scavenging activity against the methoxy radical initiated by the Fenton reaction and measured by Electron Paramagnetic Resonance (EPR). The antioxidant effects of lyophilised CA measured in beef patties containing 0.1% and 0.3% (w/w) CA stored in modified atmosphere packaging (MAP) (80% O2 and 20% CO2) was determined. A preliminary study of gelatine based film containing CA showed a strong antioxidant effect in preventing the degradation of lipid in muscle food. Thus, the present results indicate that CA extract can be used as a natural food antioxidant. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Oxidation Stability of Pig Liver Pâté with Increasing Levels of Natural Antioxidants (Grape and Tea)
Antioxidants 2015, 4(1), 102-123; doi:10.3390/antiox4010102
Received: 30 October 2014 / Revised: 7 January 2015 / Accepted: 19 January 2015 / Published: 27 January 2015
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Abstract
The present study investigated the effect of the addition of increasing levels of the natural antioxidants tea (TEA) and grape seed extracts (GRA) on the physiochemical and oxidative stability of refrigerated stored pig pâtés. In addition, a synthetic antioxidant and a control [...] Read more.
The present study investigated the effect of the addition of increasing levels of the natural antioxidants tea (TEA) and grape seed extracts (GRA) on the physiochemical and oxidative stability of refrigerated stored pig pâtés. In addition, a synthetic antioxidant and a control batch were used, thus a total of eight batches of liver pâté were prepared: CON, BHT, TEA (TEA50, TEA200 and TEA1000) and GRA (GRA50, GRA200 and GRA1000). Pâté samples were analyzed following 0, 4, 8 and 24 weeks of storage. Color parameters were affected by storage period and level of antioxidant extract. Samples with TEA200 and GRA1000 levels of extracts showed lower total color difference between 0 and 24 weeks. At the end of storage period, the lower TBARs values were obtained in samples with the highest concentration on natural extract. Overall, the evolution of volatile compounds showed an increase in those ones that arise from the lipid oxidation and samples with TEA1000 extract showed the lowest values. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Effect of Addition of Natural Antioxidants on the Shelf-Life of “Chorizo”, a Spanish Dry-Cured Sausage
Antioxidants 2015, 4(1), 42-67; doi:10.3390/antiox4010042
Received: 30 October 2014 / Accepted: 6 January 2015 / Published: 14 January 2015
Cited by 2 | PDF Full-text (1482 KB) | HTML Full-text | XML Full-text
Abstract
The dose effect of the addition of natural antioxidants (tea, chestnut, grape seed and beer extracts) on physicochemical, microbiological changes and on oxidative stability of dry-cured “chorizo”, as well as their effect during the storage under vacuum conditions was evaluated. Color parameters [...] Read more.
The dose effect of the addition of natural antioxidants (tea, chestnut, grape seed and beer extracts) on physicochemical, microbiological changes and on oxidative stability of dry-cured “chorizo”, as well as their effect during the storage under vacuum conditions was evaluated. Color parameters were significantly (p < 0.05) affected by the addition of antioxidants so that samples that contained antioxidants were more effective in maintaining color. The improving effects were dose-dependent with highest values with the dose of 50 mg/kg during ripening and depend on the extract during vacuum packaging. Addition of antioxidants decreased (p < 0.05) the oxidation, showing thiobarbituric acid reactive substances (TBARS) values below 0.4 mg MDA/kg. Natural antioxidants matched or even improved the results obtained for butylated hydroxytoluene (BHT). Regarding texture profile analysis (TPA) analysis, hardness values significantly (p < 0.001) decreased with the addition of antioxidants, obtaining the lower results with the dose of 200 mg/kg both during ripening and vacuum packaging. Antioxidants reduced the counts of total viable counts (TVC), lactic acid bacteria (LAB), mold and yeast. Free fatty acid content during ripening and under vacuum conditions showed a gradual and significant (p < 0.05) release as a result of lipolysis. At the end of ripening, the addition of GRA1000 protected chorizos from oxidative degradation. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Antioxidant Content, Antioxidant Activity, and Antibacterial Activity of Five Plants from the Commelinaceae Family
Antioxidants 2014, 3(4), 758-769; doi:10.3390/antiox3040758
Received: 11 September 2014 / Revised: 27 October 2014 / Accepted: 3 November 2014 / Published: 17 November 2014
Cited by 1 | PDF Full-text (428 KB) | HTML Full-text | XML Full-text
Abstract
Commelinaceae is a family of herbaceous flowering plants with many species used in ethnobotany, particularly in South America. However, thus far reports of their bioactivity are few and far between. The primary aim of this study was to quantify the antioxidant and [...] Read more.
Commelinaceae is a family of herbaceous flowering plants with many species used in ethnobotany, particularly in South America. However, thus far reports of their bioactivity are few and far between. The primary aim of this study was to quantify the antioxidant and antibacterial activity of five Commelinaceae methanolic leaf extracts. The antioxidant content was evaluated by the total phenolic content (TPC), total tannin content (TTC), and total flavonoid content (TFC) assays. The antioxidant activities measured were DPPH free radical scavenging (FRS), ferric reducing power (FRP), and ferrous ion chelating (FIC); of the five plants, the methanolic leaf extract of Tradescantia zebrina showed the highest antioxidant content and activity, and exhibited antibacterial activity against six species of Gram-positive and two species of Gram-negative bacteria in a range of 5–10 mg/mL based on the broth microdilution method. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Antioxidant Capacity, Cytotoxicity and Antimycobacterial Activity of Madeira Archipelago Endemic Helichrysum Dietary and Medicinal Plants
Antioxidants 2014, 3(4), 713-729; doi:10.3390/antiox3040713
Received: 19 August 2014 / Revised: 16 October 2014 / Accepted: 17 October 2014 / Published: 31 October 2014
Cited by 1 | PDF Full-text (231 KB) | HTML Full-text | XML Full-text
Abstract
The potential bioactivity of dietary and medicinal endemic Helichrysum plants from Madeira Archipelago was explored, for the first time, in order to supply new information for the general consumer. In vitro antioxidant properties were investigated using DPPH, ABTS•+, FRAP and [...] Read more.
The potential bioactivity of dietary and medicinal endemic Helichrysum plants from Madeira Archipelago was explored, for the first time, in order to supply new information for the general consumer. In vitro antioxidant properties were investigated using DPPH, ABTS•+, FRAP and β-Carotene assays, and the total phenolic content (TPC) and total flavonoid content (TFC) were also determined. Although the results generally showed a large variation among the three analyzed plants, the methanolic extracts showed the highest antioxidant capacity. Exception is made for H. devium n-hexane extract that showed good radical scavenger capacity associated to compounds with good reducing properties. In the Artemia salina toxicity assay and antimycobaterial activity, H. devium was the most potent plant with the lowest LD50 at 216.7 ± 10.4 and MIC ≤ 50 μg·mL−1. Chemometric evaluation (Principal Component Analysis—PCA) showed close interdependence between the ABTS, TPC and TFC methods and allowed to group H. devium samples. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Optimization of the Aqueous Extraction of Phenolic Compounds from Olive Leaves
Antioxidants 2014, 3(4), 700-712; doi:10.3390/antiox3040700
Received: 5 August 2014 / Revised: 27 August 2014 / Accepted: 3 September 2014 / Published: 23 October 2014
Cited by 5 | PDF Full-text (2379 KB) | HTML Full-text | XML Full-text
Abstract
Olive leaves are an agricultural waste of the olive-oil industry representing up to 10% of the dry weight arriving at olive mills. Disposal of this waste adds additional expense to farmers. Olive leaves have been shown to have a high concentration of [...] Read more.
Olive leaves are an agricultural waste of the olive-oil industry representing up to 10% of the dry weight arriving at olive mills. Disposal of this waste adds additional expense to farmers. Olive leaves have been shown to have a high concentration of phenolic compounds. In an attempt to utilize this waste product for phenolic compounds, we optimized their extraction using water—a “green” extraction solvent that has not yet been investigated for this purpose. Experiments were carried out according to a Box Behnken design, and the best possible combination of temperature, extraction time and sample-to-solvent ratio for the extraction of phenolic compounds with a high antioxidant activity was obtained using RSM; the optimal conditions for the highest yield of phenolic compounds was 90 °C for 70 min at a sample-to-solvent ratio of 1:100 g/mL; however, at 1:60 g/mL, we retained 80% of the total phenolic compounds and maximized antioxidant capacity. Therefore the sample-to-solvent ratio of 1:60 was chosen as optimal and used for further validation. The validation test fell inside the confidence range indicated by the RSM output; hence, the statistical model was trusted. The proposed method is inexpensive, easily up-scaled to industry and shows potential as an additional source of income for olive growers. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Modelling Extraction of White Tea Polyphenols: The Influence of Temperature and Ethanol Concentration
Antioxidants 2014, 3(4), 684-699; doi:10.3390/antiox3040684
Received: 2 July 2014 / Revised: 29 July 2014 / Accepted: 30 September 2014 / Published: 21 October 2014
Cited by 1 | PDF Full-text (351 KB) | HTML Full-text | XML Full-text
Abstract
The optimization of the extraction of natural antioxidants from white tea has fostered intensive research. This study has investigated the effects of ethanol-water mixtures, temperature and time on the extraction of polyphenols and antioxidant components from white tea. The response surface methodology [...] Read more.
The optimization of the extraction of natural antioxidants from white tea has fostered intensive research. This study has investigated the effects of ethanol-water mixtures, temperature and time on the extraction of polyphenols and antioxidant components from white tea. The response surface methodology was applied to identify the best extraction conditions. The best conditions to maximize the extraction of total polyphenols were: ethanol, 50%, for 47.5 min. Although the yield of polyphenols was optimal at 65 °C, the maximum antioxidant capacity was achieved with an extraction temperature of 90 °C. This study has identified the optimal conditions for the extraction of tea liquor with the best antioxidant properties. Epigallocatechin gallate, epicatechin gallate, epigallocatechin and epicatechin were extracted from white tea at concentrations up to 29.6 ± 10.6, 5.40 ± 2.09, 5.04 ± 0.20 and 2.48 ± 1.10 mg/100 g. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Analysis of Phenolic and Flavonoid Contents, and the Anti-Oxidative Potential and Lipid Peroxidation Inhibitory Activity of Methanolic Extract of Carissa opaca Roots and Its Fractions in Different Solvents
Antioxidants 2014, 3(4), 671-683; doi:10.3390/antiox3040671
Received: 23 July 2014 / Revised: 19 September 2014 / Accepted: 30 September 2014 / Published: 20 October 2014
Cited by 3 | PDF Full-text (473 KB) | HTML Full-text | XML Full-text
Abstract
The objective of the present work was to investigate the anti-oxidative potential of methanolic extract of Carissa opaca roots and its fractions in solvents of different polarities. Total phenolic (TPC) and flavonoid (TFC) contents of methanolic extract were 211.95 ± 0.78 μg/mL [...] Read more.
The objective of the present work was to investigate the anti-oxidative potential of methanolic extract of Carissa opaca roots and its fractions in solvents of different polarities. Total phenolic (TPC) and flavonoid (TFC) contents of methanolic extract were 211.95 ± 0.78 μg/mL gallic acid equivalents (GAE) and 8.35 ± 0.21 μg/mL rutin equivalents (RE), respectively. Ethyl acetate contained the highest amounts of both (TFC, 11.8 ± 0.28 RE; TPC, 342.80 ± 0.42 GAE) followed by chloroform fraction (TFC, 7.50 ± 0.14 RE; TPC, 275.85 ± 0.50 GAE). Extract and fractions displayed remarkable DPPH radical scavenging activity. EC50 values of methanolic extract was 0.88 mg/mL, while that of hexane, chloroform, ethyl acetate, n-butanolic and aqueous fractions were 0.58, 0.38, 0.29, 0.36 and 5.83 mg/mL, respectively, ethyl acetate fraction being most potent. The ethyl acetate fraction also showed the highest activity in terms of reducing power, phosphomolybdate and ABTS assays. All the fractions showed fairly good lipid peroxidation inhibitory activity, which remained almost constant over three days. Based on the results it can be concluded that roots of Carissa opaca contains phytochemicals with exploitable antioxidant, free radical scavenging, and lipid peroxidation inhibitory potential. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Syzyguim guineense Extracts Show Antioxidant Activities and Beneficial Activities on Oxidative Stress Induced by Ferric Chloride in the Liver Homogenate
Antioxidants 2014, 3(3), 618-635; doi:10.3390/antiox3030618
Received: 30 June 2014 / Revised: 15 August 2014 / Accepted: 22 August 2014 / Published: 19 September 2014
Cited by 7 | PDF Full-text (474 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study was to determine the in vitro antioxidant activity, free radical scavenging property and the beneficial effects of extracts of various parts of Syzygium guineense in reducing oxidative stress damage in the liver. The effects of extracts on [...] Read more.
The aim of this study was to determine the in vitro antioxidant activity, free radical scavenging property and the beneficial effects of extracts of various parts of Syzygium guineense in reducing oxidative stress damage in the liver. The effects of extracts on free radicals were determined on radicals DPPH, ABTS, NO and OH followed by the antioxidant properties using Ferric Reducing Antioxidant Power assay (FRAP) and hosphomolybdenum (PPMB). The phytochemical screening of these extracts was performed by determination of the phenolic content. The oxidative damage inhibition in the liver was determined by measuring malondialdehyde (MDA) as well as the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase. Overall, the bark extract of the ethanol/water or methanol showed the highest radical scavenging activities against DPPH, ABTS and OH radicals compared to the other extracts. This extract also contained the highest phenolic content implying the potential contribution of phenolic compounds towards the antioxidant activities. However, the methanol extract of the root demonstrated the highest protective effects of SOD and CAT against ferric chloride while the hydro-ethanol extract of the leaves exhibited the highest inhibitory effects on lipid peroxidation. These findings suggest that antioxidant properties of S. guineense extracts could be attributed to phenolic compounds revealed by phytochemical studies. Thus, the present results indicate clearly that the extracts of S. guineense possess antioxidant properties and could serve as free radical inhibitors or scavengers, acting possibly as primary antioxidants. The antioxidant properties of the bark extract may thus sustain its various biological activities. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)
Open AccessArticle Optimisation of Ultrasound-Assisted Extraction Conditions for Phenolic Content and Antioxidant Capacity from Euphorbia tirucalli Using Response Surface Methodology
Antioxidants 2014, 3(3), 604-617; doi:10.3390/antiox3030604
Received: 8 July 2014 / Revised: 20 August 2014 / Accepted: 25 August 2014 / Published: 17 September 2014
Cited by 5 | PDF Full-text (1422 KB) | HTML Full-text | XML Full-text
Abstract
Euphorbia tirucalli (E. tirucalli) is now widely distributed around the world and is well known as a source of traditional medicine in many countries. This study aimed to utilise response surface methodology (RSM) to optimise ultrasonic-assisted extraction (UAE) conditions for [...] Read more.
Euphorbia tirucalli (E. tirucalli) is now widely distributed around the world and is well known as a source of traditional medicine in many countries. This study aimed to utilise response surface methodology (RSM) to optimise ultrasonic-assisted extraction (UAE) conditions for total phenolic compounds (TPC) and antioxidant capacity from E. tirucalli leaf. The results showed that ultrasonic temperature, time and power effected TPC and antioxidant capacity; however, the effects varied. Ultrasonic power had the strongest influence on TPC; whereas ultrasonic temperature had the greatest impact on antioxidant capacity. Ultrasonic time had the least impact on both TPC and antioxidant capacity. The optimum UAE conditions were determined to be 50 °C, 90 min. and 200 W. Under these conditions, the E. tirucalli leaf extract yielded 2.93 mg GAE/g FW of TPC and exhibited potent antioxidant capacity. These conditions can be utilised for further isolation and purification of phenolic compounds from E. tirucalli leaf. Full article
(This article belongs to the Special Issue Natural Products as Antioxidants)

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