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Special Issue "The Antioxidant Capacities of Natural Products 2019"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: 31 October 2019

Special Issue Editors

Guest Editor
Dr. Susana M. Cardoso

Department of Chemistry, University of Aveiro, Aveiro, Portugal
Website | E-Mail
Interests: traditional medicine; medicinal plants; healthy foods; food supplements and nutraceuticals; bioactivity
Guest Editor
Dr. Alessia Fazio

Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende , Italy
Website | E-Mail
Phone: +39 0984493013
Interests: food matrices of plant origin, antioxidant capacities, antiproliferative activity, anti-inflammatory properties, glucans, pectins, seed oils, citrus essential oils, fatty acids, biopolymer synthesis, active packaging

Special Issue Information

Dear Colleagues,

Antioxidants play an important role in the defense network by inhibiting the free radical-mediated oxidation of lipids, proteins, sugars, and also DNA. Their activity is of significance both in foods, for the prevention of oxidation and prolongation of shelf-life, and in the body, for dealing with oxidative stress, which is involved in the pathogenesis of various diseases, such as cardiovascular and neurodegenerative diseases and cancer, and in aging. Natural compounds with free radical-scavenging capacity contained in plants, fruits, and vegetables have received much attention and are being extensively used as antioxidants in the food, cosmetic, and pharmaceutical fields to replace synthetic antioxidants, whose use is often restricted because of their carcinogenic effects. The search for new natural compounds with antioxidant activities is a growing research area.

The aim of this Special Issue is to highlight the recent advances on antioxidant natural compounds. This Special Issue may include original research articles and reviews on new extraction procedures; isolation, purification, and characterization of new compounds; in vitro and in vivo studies on the antioxidant properties of extracts, fractions, synergistic mixtures, and isolated compounds and their possible employment to treat human diseases. Studies dealing with new formulations containing antioxidants (including polymers for active packaging) are also welcome.

Dr. Susana M. Cardoso
Dr. Alessia Fazio
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • New antioxidant natural compounds
  • Extraction, isolation, and characterization of natural antioxidants
  • Mechanism of action of antioxidant natural compounds
  • Synergistic activity of natural compounds
  • Strategies combining natural compounds and conventional therapeutic approaches
  • Pharmacological evidence (in vitro, in vivo) related to antioxidant activities
  • Antioxidant activities and inflammation-related disorders
  • New formulations containing antioxidants

Published Papers (18 papers)

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Research

Open AccessArticle
Target-Guided Isolation of Three Main Antioxidants from Mahonia bealei (Fort.) Carr. Leaves Using HSCCC
Molecules 2019, 24(10), 1907; https://doi.org/10.3390/molecules24101907
Received: 1 May 2019 / Revised: 14 May 2019 / Accepted: 15 May 2019 / Published: 17 May 2019
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Abstract
Mahonia bealei (Fort.) Carr. is an economically important plant that is widely cultivated in Southwest China. Its leaves are commonly used for tea and contain an abundance of antioxidant compounds. However, methods of the systematic purification of antioxidants from M. bealei are lacking. [...] Read more.
Mahonia bealei (Fort.) Carr. is an economically important plant that is widely cultivated in Southwest China. Its leaves are commonly used for tea and contain an abundance of antioxidant compounds. However, methods of the systematic purification of antioxidants from M. bealei are lacking. In this study, antioxidants from this plant were effectively and rapidly enriched. First, antioxidants were screened using online 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH)–high performance liquid chromatography (HPLC), followed by separation using high-speed countercurrent chromatography with an optical solvent system composed of n-hexane/ethyl acetate/methanol/water (1:5:1:5, v/v/v/v). Three phenolics—chlorogenic acid (1, 8.3 mg), quercetin-3-O-β-d-glucopyranoside (2, 20.5 mg), and isorhamnetin-3-O-β-d-glucopyranoside (3, 28.4 mg)—were obtained from the ethyl acetate-soluble fraction (240 mg) by one-step separation. The chemical structures of the phenolics were characterized by MS and NMR techniques, and the purity of each compound was >92.0% as determined by HPLC. The isolated compounds were assessed by scavenging activities on DPPH and superoxide radicals as well as cytoprotective assays, all of which showed similar trends regarding the antioxidant capacities of the compounds. Moreover, compounds 13 significantly attenuated the lipid peroxidation and antioxidant enzyme activities in H2O2-treated RAW264.7 cells. Our study demonstrated the efficiency of a newly developed integrative system for the comprehensive characterization of pure compounds from M. bealei, which will allow their use as reference substances. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Comparative Study of Phenolic Profiles, Antioxidant and Antiproliferative Activities in Different Vegetative Parts of Ramie (Boehmeria nivea L.)
Molecules 2019, 24(8), 1551; https://doi.org/10.3390/molecules24081551
Received: 22 March 2019 / Revised: 9 April 2019 / Accepted: 12 April 2019 / Published: 19 April 2019
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Abstract
Ramie (Boehmeria nivea L.) is usually cultivated as a fiber crop, but it is also well known for its potential use in animal feeding with viable commercial applications. In this study, the phenolics profile as well as cellular antioxidant and antiproliferative activities [...] Read more.
Ramie (Boehmeria nivea L.) is usually cultivated as a fiber crop, but it is also well known for its potential use in animal feeding with viable commercial applications. In this study, the phenolics profile as well as cellular antioxidant and antiproliferative activities were investigated in free and bound fractions of six different vegetative parts from Boehmeria nivea L. The highest total phenolic content was observed in bud (4585 ± 320 mg GAE/100 g DW), whereas root and petiole had the lowest total phenolic contents, 442.8 ± 9.8 and 630.9 ± 27.0 mg GAE/100 g DW, respectively. Likewise, phloem had the most abundant total flavonoids (2755 ± 184 mg CE/100 g DW), whereas the lowest flavonoid contents was found in root and petiole, 636.9 ± 44.2 and 797.4 ± 87.6 mg CE/100 g DW, respectively. Xylem and bud depicted remarkable antioxidant and antiproliferative activities, which could be explained by their diverse phenolic composition, especially chlorogenic acid and epicatechin. The Boehmeria nivea L. plant might be a valuable resource for high value-added phenolic compounds used in food and non-food industries. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Phytochemical Diversity in Rhizomes of Three Reynoutria Species and their Antioxidant Activity Correlations Elucidated by LC-ESI-MS/MS Analysis
Molecules 2019, 24(6), 1136; https://doi.org/10.3390/molecules24061136
Received: 25 February 2019 / Revised: 11 March 2019 / Accepted: 14 March 2019 / Published: 21 March 2019
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Abstract
The rhizome of Reynoutria japonica is a well-known traditional herb (Hu zhang) used in East Asia to treat various inflammatory diseases, infections, skin diseases, scald, and hyperlipidemia. It is also one of the richest natural sources of resveratrol. Although, it has been recently [...] Read more.
The rhizome of Reynoutria japonica is a well-known traditional herb (Hu zhang) used in East Asia to treat various inflammatory diseases, infections, skin diseases, scald, and hyperlipidemia. It is also one of the richest natural sources of resveratrol. Although, it has been recently included in the European Pharmacopoeia, in Europe it is still an untapped resource. Some of the therapeutic effects are likely to be influenced by its antioxidant properties and this in turn is frequently associated with a high stilbene content. However, compounds other than stilbenes may add to the total antioxidant capacity. Hence, the aim of this research was to examine rhizomes of R. japonica and the less studied but morphologically similar species, R. sachalinensis and R. x bohemica for their phytochemical composition and antioxidant activity and to clarify the relationship between the antioxidant activity and the components by statistical methods. HPLC/UV/ESI-MS studies of three Reynoutria species revealed 171 compounds, comprising stilbenes, carbohydrates, procyanidins, flavan-3-ols, anthraquinones, phenylpropanoids, lignin oligomers, hydroxycinnamic acids, naphthalenes and their derivatives. Our studies confirmed the presence of procyanidins with high degree of polymerization, up to decamers, in the rhizomes of R. japonica and provides new data on the presence of these compounds in other Reynoutria species. A procyanidin trimer digallate was described for the first time in, the studied plants. Moreover, we tentatively identified dianthrone glycosides new for these species and previously unrecorded phenylpropanoid disaccharide esters and hydroxycinnamic acid derivatives. Furthermore, compounds tentatively annotated as lignin oligomers were observed for the first time in the studied species. The rhizomes of all Reynoutria species exhibited strong antioxidant activity. Statistical analysis demonstrated that proanthocyanidins should be considered as important contributors to the total antioxidant capacity. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Chromatographic Analysis and Anti-Oxidative Property of Naoxinqing Tablet, a Proprietary Preparation of Diospyros Kaki Leaves
Molecules 2019, 24(6), 1101; https://doi.org/10.3390/molecules24061101
Received: 31 October 2018 / Revised: 8 March 2019 / Accepted: 11 March 2019 / Published: 20 March 2019
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Abstract
The Naoxinqing (NXQ) tablet is a standardised proprietary herbal product containing an extract of persimmon leaves (Diospyros kaki) for the management of cardio- and cerebrovascular diseases. Although previous reports suggested that the efficacy of NXQ is at least partly mediated by [...] Read more.
The Naoxinqing (NXQ) tablet is a standardised proprietary herbal product containing an extract of persimmon leaves (Diospyros kaki) for the management of cardio- and cerebrovascular diseases. Although previous reports suggested that the efficacy of NXQ is at least partly mediated by its anti-oxidative property, the anti-oxidative effect of the major components of NXQ has not been studied systematically. For quality control purposes, only analytical methods limited to 3 marker analytes have been reported, the extent to which the other components affect efficacy has not been explored. In this study, we developed an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC MS/MS) method for the identification of seven analytes (kaempferol-3-O-glucoside (astragalin), quercetin-3-O-galactoside (hypericin), quercetin-3-O-glucoside (isoquercitin), kaempferol, 3,4-dihydroxybenzoic acid (protocatechuic acid), and furan-2-carboxylic acid (pyromucic acid) and quercetin) in the NXQ. This is the first method reported and validated for the quantification of the seven major secondary metabolites in NXQ. The results for the quantified analytes were then compared in 15 different batches of NXQ. The variation observed in the seven components highlights the need to quantify key bioactive components to ensure product consistency. Radical scavenging activity and abundance was used to rank the analytes. The anti-oxidative effects of NXQ were examined using cultured human vascular endothelial cells (EA.hy926). Corrected 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) activity results revealed that quercetin and kaempferol have the strongest anti-oxidant capacity in the extract. Both quercetin and kaempferol significantly inhibited the hydrogen peroxide (H2O2)-induced EA.hy926 cell injury and intracellular reactive oxygen species (ROS) generation. In conclusion, we established and validated an UPLC-MS/MC method for the analysis of major bioactive components in the NXQ and demonstrated that its anti-oxidative property may play a critical role in cerebrovascular protection. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Antioxidant Activities of Vaccinium vitis-idaea L. Leaves within Cultivars and Their Phenolic Compounds
Molecules 2019, 24(5), 844; https://doi.org/10.3390/molecules24050844
Received: 1 February 2019 / Revised: 22 February 2019 / Accepted: 22 February 2019 / Published: 27 February 2019
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Abstract
Lingonberry leaves are the subject of numerous studies because of antioxidant properties, positive influence on the health and potential use in the prevention and treatment of chronic diseases. In this work, the radical scavenging, reducing, chelating activities, and phenolic composition of ten lingonberry [...] Read more.
Lingonberry leaves are the subject of numerous studies because of antioxidant properties, positive influence on the health and potential use in the prevention and treatment of chronic diseases. In this work, the radical scavenging, reducing, chelating activities, and phenolic composition of ten lingonberry leaves cultivars, one subspecies, and one variety were investigated. Furthermore, the antioxidant activity of individual phenolic compounds, that can be found in lingonberry leaves, were analyzed, and structure-activity relationship was determined. Wide diversity for phenolic profile and antioxidant properties of lingonberry leaves has been observed in the present material. Cultivars ‘Kostromskaja rozovaja’, ‘Rubin’, and Vaccinium vitis-idaea var. leucocarpum surpassed all others tested cultivars and lower taxa by contents of phenolic compounds and antioxidant activity. Leaves of lingonberry cultivars and lower taxa are rich in arbutin, flavonol glycosides, proanthocyanidins, and the latter were considered to be the major contributor to antioxidant properties of lingonberry leaves. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Fish Protein and Lipid Interactions on the Digestibility and Bioavailability of Starch and Protein from Durum Wheat Pasta
Molecules 2019, 24(5), 839; https://doi.org/10.3390/molecules24050839
Received: 14 December 2018 / Revised: 18 February 2019 / Accepted: 20 February 2019 / Published: 27 February 2019
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Abstract
This research focussed on the utilisation of salmon protein and lipid to manipulate pasta’s glycaemic index and protein digestibility. Salmon fish (Oncorhynchus tschawytscha) powder (SFP) supplemented pasta flour in amounts from 5% to 20% (w/w). Inclusion of [...] Read more.
This research focussed on the utilisation of salmon protein and lipid to manipulate pasta’s glycaemic index and protein digestibility. Salmon fish (Oncorhynchus tschawytscha) powder (SFP) supplemented pasta flour in amounts from 5% to 20% (w/w). Inclusion of SFP lead to a significant reduction in starch digestibility and hence the potential glycaemic values of pasta (experimental pasta being up to 143% lower than control values). SFP addition to pasta increased the release of phenolic compounds from pasta during both gastric digestion (179%) and pancreatic digestion (133%) in comparison to the control sample. At the same time, the antioxidant activity of the digested pasta was increased by up to 263% (gastric) and 190% (pancreatic) in comparison to durum wheat pasta alone. Interestingly, although protein levels increased with incorporation of SFP, the digestibility values of the protein decreased from 86.41% for the control pasta to 81.95% for 20% SFP pasta. This may indicate that there are interactions between phenols and protein in the pasta samples which affect overall protein digestibility levels. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Increased Phenolic Content and Enhanced Antioxidant Activity in Fermented Glutinous Rice Supplemented with Fu Brick Tea
Molecules 2019, 24(4), 671; https://doi.org/10.3390/molecules24040671
Received: 30 January 2019 / Revised: 10 February 2019 / Accepted: 10 February 2019 / Published: 14 February 2019
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Abstract
Glutinous rice-based foods have a long history are consumed worldwide. They are also in great demand for the pursuit of novel sensory and natural health benefits. In this study, we developed a novel fermented glutinous rice product with the supplementation of Fu brick [...] Read more.
Glutinous rice-based foods have a long history are consumed worldwide. They are also in great demand for the pursuit of novel sensory and natural health benefits. In this study, we developed a novel fermented glutinous rice product with the supplementation of Fu brick tea. Using in vitro antioxidant evaluation and phenolic compounds analysis, fermentation with Fu brick tea increased the total phenolic content and enhanced the antioxidant activity of glutinous rice, including scavenging of 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical, 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical, and hydroxyl radical, ferric-reducing antioxidant power, and ferric ion reducing power and iron chelating capability. Besides, compared with traditional fermented glutinous rice, this novel functional food exhibited a stronger activity for protecting DNA against hydroxyl radical-induced oxidation damage. Quantitative analysis by HPLC identified 14 compounds covering catechins and phenolic acids, which were considered to be positively related to the enhanced antioxidant capability. Furthermore, we found that 80% ethanol was a suitable extract solvent compared with water, because of its higher extraction efficiency and stronger functional activities. Our results suggested that this novel fermented glutinous rice could serve as a nutraceutical food/ingredient with special sensory and functional activities. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
HPLC Profile of Longan (cv. Shixia) Pericarp-Sourced Phenolics and Their Antioxidant and Cytotoxic Effects
Molecules 2019, 24(3), 619; https://doi.org/10.3390/molecules24030619
Received: 4 January 2019 / Revised: 31 January 2019 / Accepted: 5 February 2019 / Published: 11 February 2019
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Abstract
Longan (Dimocarpus longan Lour.) pericarp, the main by-product of aril and pulp processing, is abundant in phenolic compounds and worthy of further utilization. The present work firstly reported HPLC analysis and in vitro antioxidant evaluation of longan (cv. Shixia) pericarp-derived phenolics (LPPs), [...] Read more.
Longan (Dimocarpus longan Lour.) pericarp, the main by-product of aril and pulp processing, is abundant in phenolic compounds and worthy of further utilization. The present work firstly reported HPLC analysis and in vitro antioxidant evaluation of longan (cv. Shixia) pericarp-derived phenolics (LPPs), the purified longan pericarp extract (LPE), as well as their cytotoxic effect on lung cancer cell line, A549. The results indicated that the purified LPE had significant amounts of phenolics, with content of 57.8 ± 0.6 mg of gallic acid equivalents per gram of dry longan pericarp (mg GAE·g−1 DLP), which consisted of six phenolic compounds (A–F), including protocatechuic acid (A), isoscopoletin (B), quercetin (C), ellagic acid (D), corilagin (E), and proanthocyanidins C1 (F). Antioxidant assays showed that LPPs (10 μM) and LPE (1.0 mg·mL−1) had certain antioxidant activities, in which corilagin (E) possessed the best DPPH radical scavenging rate 71.8 ± 0.5% and •OH inhibition rate 75.9 ± 0.3%, and protocatechuic acid (A) exhibited the strongest Fe2+ chelating ability 36.4 ± 0.7%. In vitro cytotoxic tests suggested that LPPs had different effect on A549 cell line, in which corilagin (E) exhibited potent cytotoxicity with an IC50 value of 28.8 ± 1.2 μM. These findings were further confirmed by cell staining experiments. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Preparation and Evaluation of Novel Transfersomes Combined with the Natural Antioxidant Resveratrol
Molecules 2019, 24(3), 600; https://doi.org/10.3390/molecules24030600
Received: 23 December 2018 / Revised: 3 February 2019 / Accepted: 6 February 2019 / Published: 8 February 2019
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Abstract
Resveratrol (tran-3,5,4′-trihydroxystibene, RSV) is a kind of polyphenol which has anti-inflammatory, antioxidant, anti-allergy, and anti-cancer properties, as well as being a scavenger of free radicals and preventing cardiovascular diseases. However, it is quite unstable in light, heat, and other conditions, and [...] Read more.
Resveratrol (tran-3,5,4′-trihydroxystibene, RSV) is a kind of polyphenol which has anti-inflammatory, antioxidant, anti-allergy, and anti-cancer properties, as well as being a scavenger of free radicals and preventing cardiovascular diseases. However, it is quite unstable in light, heat, and other conditions, and decays easily due to environmental factors. For these reasons, this study used a new type of carrier, transfersome, to encapsulate RSV. Transfersome consists of phosphatidyl choline (PC) from a liposomal system and non-ionic edge activators (EA). EA are an important ingredient in the formulation of transfersome; they can enhance the flexibility of the lipid bimolecular membrane of transfersome. Due to its ultradeformability, it also allows drugs to penetrate the skin, even through the stratum corneum. We hope that this new encapsulation technique will improve the stability and enhance the permeability of RSV. Concluding all the tested parameters, the best production condition was 5% PC/EA (3:1) and 5% ethanol in distilled water, with an ultrasonic bath and stirring at 500 rpm, followed by high pressure homogenization. The optimal particle size was 40.13 ± 0.51 nm and the entrapment efficiency (EE) was 59.93 ± 0.99%. The results of antioxidant activity analysis showed that transfersomes were comparable to the RSV group (unencapsulated). During in vitro transdermal delivery analysis, after 6 h, D1-20(W) increased 27.59% by accumulation. Cell viability assay showed that the cytotoxicity of D3-80(W) was reduced by 34.45% compared with the same concentration of RSV. Therefore, we successfully prepared RSV transfersomes and also improved the stability, solubility, and safety of RSV. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Flowers of Astragalus membranaceus var. mongholicus as a Novel High Potential By-Product: Phytochemical Characterization and Antioxidant Activity
Molecules 2019, 24(3), 434; https://doi.org/10.3390/molecules24030434
Received: 6 January 2019 / Revised: 22 January 2019 / Accepted: 22 January 2019 / Published: 25 January 2019
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Abstract
The root of Astragalus membranaceus var. mongholicus is one of the most popular herbal medicines worldwide. In order to increase the yield of underground roots of A. membranaceus var. mongholicus, its flowers (AMF) have often been removed in their flowering stage, which [...] Read more.
The root of Astragalus membranaceus var. mongholicus is one of the most popular herbal medicines worldwide. In order to increase the yield of underground roots of A. membranaceus var. mongholicus, its flowers (AMF) have often been removed in their flowering stage, which produces the flowers as waste being discarded. To explore its phytochemicals and potential value for utilization, the antioxidant activities of extracts from AMF were evaluated by a free radical scavenging assay and reducing power assay. The total phenols and flavonoids, as well as the individual compounds, in different extracts of AMF were also investigated. The results showed that the extract ME obtained from AMF through macroporous resins separation exhibited strong antioxidant activities, which were close to those of positive control BHT. ME was rich in phenolic acids and flavonoids, and the contents reached 108.42 mg gallic acid equivalents/g and 265.70 mg rutin equivalents/g, respectively. A total of 31 compounds, including four phenolic acids, nineteen flavonoids, three isoflavones, two pterocarpans, and three saponins, were identified using UPLC-QTOF-MS in ME. Quantitative analysis of sixteen components in the extracts of AMF showed that flavonoids were the predominant constituents, especially for the compounds of hyperoside, rutin, and isorhamnetin-3-O-β-d-glucoside. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Antioxidant Mechanisms of Echinatin and Licochalcone A
Received: 3 December 2018 / Revised: 17 December 2018 / Accepted: 18 December 2018 / Published: 20 December 2018
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Abstract
Echinatin and its 1,1-dimethyl-2-propenyl derivative licochalcone A are two chalcones found in the Chinese herbal medicine Gancao. First, their antioxidant mechanisms were investigated using four sets of colorimetric measurements in this study. Three sets were performed in aqueous solution, namely Cu2+ [...] Read more.
Echinatin and its 1,1-dimethyl-2-propenyl derivative licochalcone A are two chalcones found in the Chinese herbal medicine Gancao. First, their antioxidant mechanisms were investigated using four sets of colorimetric measurements in this study. Three sets were performed in aqueous solution, namely Cu2+-reduction, Fe3+-reduction, and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•)-scavenging measurements, while 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•)-scavenging colorimetric measurements were conducted in methanol solution. The four sets of measurements showed that the radical-scavenging (or metal-reduction) percentages for both echinatin and licochalcone A increased dose-dependently. However, echinatin always gave higher IC50 values than licochalcone A. Further, each product of the reactions of the chalcones with DPPH• was determined using electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS). The UPLC-ESI-Q-TOF-MS/MS determination for echinatin yielded several echinatin–DPPH adduct peaks (m/z 662, 226, and 196) and dimeric echinatin peaks (m/z 538, 417, and 297). Similarly, that for licochalcone A yielded licochalcone A-DPPH adduct peaks (m/z 730, 226, and 196) and dimeric licochalcone A peaks (m/z 674 and 553). Finally, the above experimental data were analyzed using mass spectrometry data analysis techniques, resonance theory, and ionization constant calculations. It was concluded that, (i) in aqueous solution, both echinatin and licochalcone A may undergo an electron transfer (ET) and a proton transfer (PT) to cause the antioxidant action. In addition, (ii) in alcoholic solution, hydrogen atom transfer (HAT) antioxidant mechanisms may also occur for both. HAT may preferably occur at the 4-OH, rather than the 4′-OH. Accordingly, the oxygen at the 4-position participates in radical adduct formation (RAF). Lastly, (iii) the 1,1-dimethyl-2-propenyl substituent improves the antioxidant action in both aqueous and alcoholic solutions. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Dual Effect of Glucuronidation of a Pyrogallol-Type Phytophenol Antioxidant: A Comparison between Scutellarein and Scutellarin
Molecules 2018, 23(12), 3225; https://doi.org/10.3390/molecules23123225
Received: 16 November 2018 / Revised: 5 December 2018 / Accepted: 6 December 2018 / Published: 6 December 2018
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Abstract
To explore whether and how glucuronidation affects pyrogallol-type phytophenols, scutellarein and scutellarin (scutellarein-7-O-glucuronide) were comparatively investigated using a set of antioxidant analyses, including spectrophotometric analysis, UV-vis spectra analysis, and ultra-performance liquid chromatography coupled with electrospray ionization-quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) [...] Read more.
To explore whether and how glucuronidation affects pyrogallol-type phytophenols, scutellarein and scutellarin (scutellarein-7-O-glucuronide) were comparatively investigated using a set of antioxidant analyses, including spectrophotometric analysis, UV-vis spectra analysis, and ultra-performance liquid chromatography coupled with electrospray ionization-quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) analysis. In spectrophotometric analyses of the scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+•), and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radicals (PTIO) and the reduction of Cu2+ ions, scutellarein showed lower IC50 values than scutellarin. However, in O2-scavenging spectrophotometric analysis, scutellarein showed higher IC50 value than scutellarin. The analysis of UV-Vis spectra obtained after the Fe2+-chelating reaction of scutellarin showed a typical UV-Vis peak (λmax = 611 nm), while scutellarein showed no typical peak. In UPLC-ESI-Q-TOF-MS/MS analysis, mixing of scutellarein with DPPH yielded MS peaks (m/z 678, 632, 615, 450, 420, 381, 329, 300, 288, 227, 196, 182, 161, and 117) corresponding to the scutellarein-DPPH adduct and an MS peak (m/z 570) corresponding to the scutellarein-scutellarein dimer. Scutellarin, however, generated no MS peak. On the basis of these findings, it can be concluded that glucuronidation of pyrogallol-type phytophenol antioxidants has a dual effect. On the one hand, glucuronidation can decrease the antioxidant potentials (except for O2 scavenging) and further lower the possibility of radical adduct formation (RAF), while on the other hand, it can enhance the O2-scavenging and Fe2+-chelating potentials. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
A Null B-Ring Improves the Antioxidant Levels of Flavonol: A Comparative Study between Galangin and 3,5,7-Trihydroxychromone
Molecules 2018, 23(12), 3083; https://doi.org/10.3390/molecules23123083
Received: 6 November 2018 / Revised: 22 November 2018 / Accepted: 23 November 2018 / Published: 26 November 2018
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Abstract
To clarify the role of the B-ring in antioxidant flavonols, we performed a comparative study between galangin with a null B-ring and 3,5,7-trihydroxychromone without a B-ring using five spectrophotometric assays, namely, O2-scavenging, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH [...] Read more.
To clarify the role of the B-ring in antioxidant flavonols, we performed a comparative study between galangin with a null B-ring and 3,5,7-trihydroxychromone without a B-ring using five spectrophotometric assays, namely, O2-scavenging, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH)-scavenging, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide radical-scavenging, 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) radical-scavenging, and Fe3+-reducing activity. The DPPH-scavenging reaction products of these assays were further analyzed by ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) technology. In the five spectrophotometric assays, galangin and 3,5,7-trihydroxychromone dose-dependently increased their radical-scavenging (or Fe3+-reducing) percentages. However, galangin always gave lower IC50 values than those of 3,5,7-trihydroxychromone. In the UPLC-ESI-Q-TOF-MS/MS analysis, galangin yielded galangin-DPPH adduct MS peaks (m/z 662, 434, 301, 227,196, and 151) and galangin-galangin dimer MS peaks (m/z 538, 385, 268, 239, 211, 195, and 151). 3,5,7-Trihydroxychromone, however, only generated m/z 3,5,7-trihydroxychromone-DPPH adduct MS peaks (m/z 586, 539, 227, 196, and 136). In conclusion, both galangin and 3,5,7-trihydroxychromone could similarly undergo multiple antioxidant pathways, including redox-dependent pathways (such as electron transfer (ET) and ET plus proton transfer (PT)) and a non-redox-dependent radical adduct formation (RAF) pathway; thus, the null B-ring could hardly change their antioxidant pathways. However, it did improve their antioxidant levels in these pathways. Such improvement of the B-ring toward an antioxidant flavonol is associated with its π-π conjugation, which can provide more resonance forms and bonding sites. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Dragon’s Blood Sap: Storage Stability and Antioxidant Activity
Molecules 2018, 23(10), 2641; https://doi.org/10.3390/molecules23102641
Received: 26 September 2018 / Revised: 6 October 2018 / Accepted: 8 October 2018 / Published: 15 October 2018
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Abstract
Currently, consumers are demanding additive-free, fresher, and more-natural products. Dragon’s Blood Sap (DBS), the deep red latex of the specie of tree Croton lechleri (Müll. Arg.), contains a high concentration of phenolic compounds of great interest for the food, pharmaceutical, and cosmetic industries. [...] Read more.
Currently, consumers are demanding additive-free, fresher, and more-natural products. Dragon’s Blood Sap (DBS), the deep red latex of the specie of tree Croton lechleri (Müll. Arg.), contains a high concentration of phenolic compounds of great interest for the food, pharmaceutical, and cosmetic industries. These chemical compounds are highly susceptible to degradation. Therefore, DBS storage stability and its photo-oxidation was studied by Fourier transform infrared spectroscopy (FT-IR) and UV-Vis spectrophotometry for 39 days at different temperatures (4–21 °C) and relative humidities (0–56%), as well as under UV light exposure. It was observed that the degradation of phenolic compounds was reduced at 0% relative humidity (RH), not showing a significant effect of temperature in the range studied. UV light irradiation degraded DBS in a 20%. DBS has an exceptional high and stable antioxidant content (≥93% inhibition percentage of DPPH), which makes it a unique property to consider the DBS as an antioxidant agent or ingredient for consumer products formulations. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Polyphenol-Rich Extracts from Cotoneaster Leaves Inhibit Pro-Inflammatory Enzymes and Protect Human Plasma Components against Oxidative Stress In Vitro
Molecules 2018, 23(10), 2472; https://doi.org/10.3390/molecules23102472
Received: 14 August 2018 / Revised: 9 September 2018 / Accepted: 20 September 2018 / Published: 26 September 2018
Cited by 1 | PDF Full-text (1465 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The present study investigated the phenolic profile and biological activity of dry extracts from leaves of C. bullatus, C. zabelii and C. integerrimus—traditional medicinal and dietary plants—and evaluated their potential in adjunctive therapy of cardiovascular diseases. Complementary UHPLC-PDA-ESI-MS3, HPLC-PDA-fingerprint, [...] Read more.
The present study investigated the phenolic profile and biological activity of dry extracts from leaves of C. bullatus, C. zabelii and C. integerrimus—traditional medicinal and dietary plants—and evaluated their potential in adjunctive therapy of cardiovascular diseases. Complementary UHPLC-PDA-ESI-MS3, HPLC-PDA-fingerprint, Folin-Ciocalteu, and n-butanol/HCl assays of the extracts derived by fractionated extraction confirmed that they are rich in structurally diverse polyphenols (47 analytes, content up to 650.8 mg GAE/g dw) with proanthocyanidins (83.3–358.2 mg CYE/g) dominating in C. bullatus and C. zabelii, and flavonoids (53.4–147.8 mg/g) in C. integerrimus. In chemical in vitro tests of pro-inflammatory enzymes (lipoxygenase, hyaluronidase) inhibition and antioxidant activity (DPPH, FRAP), the extracts effects were dose-, phenolic- and extraction solvent-dependent. The most promising polyphenolic extracts were demonstrated to be effective antioxidants in a biological model of human blood plasma—at in vivo-relevant levels (1–5 µg/mL) they normalized/enhanced the non-enzymatic antioxidant capacity of plasma and effectively prevented peroxynitrite-induced oxidative/nitrative damage of plasma proteins and lipids. As demonstrated in cytotoxicity tests, the extracts were safe—they did not affect viability of human peripheral blood mononuclear cells. In conclusion, Cotoneaster leaves may be useful in development of natural-based products, supporting the treatment of oxidative stress/inflammation-related chronic diseases, including cardiovascular disorders. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Geographic Variation in the Chemical Composition and Antioxidant Properties of Phenolic Compounds from Cyclocarya paliurus (Batal) Iljinskaja Leaves
Molecules 2018, 23(10), 2440; https://doi.org/10.3390/molecules23102440
Received: 31 August 2018 / Revised: 18 September 2018 / Accepted: 22 September 2018 / Published: 24 September 2018
Cited by 3 | PDF Full-text (2191 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Cyclocarya paliurus has been widely used as an ingredient in functional foods in China. However, the antioxidant properties of phenolic compounds and the effect of the plant origin remain unclear. The present study evaluated the geographical variation of this plant in term of [...] Read more.
Cyclocarya paliurus has been widely used as an ingredient in functional foods in China. However, the antioxidant properties of phenolic compounds and the effect of the plant origin remain unclear. The present study evaluated the geographical variation of this plant in term of its phenolic composition and antioxidant activities based on leaf materials collected from five regions. high-performance liquid chromatography (HPLC) analysis showed that there are three major components, quercetin-3-O-glucuronide, kaempferol-3-O-glucuronide, and kaempferol-3-O-rhamnoside, and their contents varied significantly among sampling locations. The investigated phenolic compounds showed substantial antioxidant activities, both in vitro and in vivo, with the highest capacity observed from Wufeng and Jinzhongshan. Correlation analysis revealed that quercetin and kaempferol glycosides might be responsible for the antioxidant activities. Our results indicate the importance of geographic origin, with sunny hours and temperature as the main drivers affecting the accumulation of C. paliurus phenolics and their antioxidant properties. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
The Effects of Cold Saponification on the Unsaponified Fatty Acid Composition and Sensory Perception of Commercial Natural Herbal Soaps
Molecules 2018, 23(9), 2356; https://doi.org/10.3390/molecules23092356
Received: 21 August 2018 / Revised: 7 September 2018 / Accepted: 12 September 2018 / Published: 14 September 2018
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Abstract
Saponification is the process in which triglycerides are combined with a strong base to form fatty acid metal salts during the soap-making process. The distribution of unsaturated and saturated fatty acid determines the hardness, aroma, cleansing, lather, and moisturizing abilities of soaps. Plant [...] Read more.
Saponification is the process in which triglycerides are combined with a strong base to form fatty acid metal salts during the soap-making process. The distribution of unsaturated and saturated fatty acid determines the hardness, aroma, cleansing, lather, and moisturizing abilities of soaps. Plant extracts, such as rosemary, vegetable, and essential oils are frequently added to soaps to enhance quality and sensory appeal. Three natural soaps were formulated using cold saponification to produce a base or control bar (BB), hibiscus rosehip bar (H), and a forest grove bar (FG). Rosemary extract (R) or essential oil (A) blends were added as additives to each formulation prior to curing to evaluate the effects of natural plant additives on the lipid composition and sensory characteristics of these natural herbal soaps. A total of seven natural soaps, three without additives (BB, H, FG) and four with additives (BBR, HA, FGR, FGA), were manufactured and studied. The majority (86–99%) of the polyunsaturated fatty acids (5.0–7.0 µg/mg) remained unsaponified in the manufactured natural soaps regardless of feedstock used. Principal component analysis (PCA) analyses showed the unsaponifiable fatty acids were different in the hibiscus bar compared to the other bars. There was a very strong correlation between the content of unsaponified C18:3n3 and C18:1n9 in all natural soaps. These results indicate that unsaponified fatty acids are important contributors to the quality and overall sensory perception and preference of natural herbal soaps following manufacturing by cold saponification. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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Open AccessArticle
Walnut Protein Hydrolysates Play a Protective Role on Neurotoxicity Induced by d-Galactose and Aluminum Chloride in Mice
Molecules 2018, 23(9), 2308; https://doi.org/10.3390/molecules23092308
Received: 16 August 2018 / Revised: 4 September 2018 / Accepted: 7 September 2018 / Published: 10 September 2018
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Abstract
In recent years, with an increase in the aging population, neurodegenerative diseases have attracted more and more attention. This study aimed to investigate the potential neuroprotective effect of defatted walnut meal protein hydrolysates (DWMPH) on neurotoxicity induced by d-galactose (d-gal) [...] Read more.
In recent years, with an increase in the aging population, neurodegenerative diseases have attracted more and more attention. This study aimed to investigate the potential neuroprotective effect of defatted walnut meal protein hydrolysates (DWMPH) on neurotoxicity induced by d-galactose (d-gal) and aluminum chloride (AlCl3) in mice. The animal models were established by combining treatments with d-gal (200 mg/kg/day, subcutaneously) and AlCl3 (100 mg/kg in drinking water) for 90 days. During the 90 days, 1 g/kg of DWMPH was administrated orally every day. The results indicated that DWMPH treatment alleviated oxidative stress, reversed cholinergic dysfunction, and suppressed the release of proinflammatory cytokines in the brains of d-gal + AlCl3-treated mice, and thus improving the learning and memory functions of these mice, which was closely correlated with the strong antioxidant activity of DWMPH. This finding suggests that DWMPH might be a promising dietary supplement in improving neuronal dysfunctions of the brain. Full article
(This article belongs to the Special Issue The Antioxidant Capacities of Natural Products 2019)
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