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Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity
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Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Bioactives and Nutraceuticals".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 17016

Special Issue Editors

Dr. Lijun Zhou

E-Mail Website
Guest Editor
College of Life Science, Sichuan Agricultural University, Ya’an 625014, China
Interests: essential oil; natural products; bioactive compounds
Special Issues, Collections and Topics in MDPI journals
Dr. Shiling Feng

E-Mail Website
Guest Editor
College of Life Science, Sichuan Agricultural University, Ya’an 625014, China
Interests: herbal medicine; natural extract; molecular biology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Natural antioxidants, especially polyphenols and polysaccharides, exhibit a wide range of biological effects, including anti-inflammatory, antioxidants, anti-aging, anti-atherosclerosis, and anticancer. Their health benefits are mainly attributed to the anti-oxidative capacity of quenching free radical species in vitro or triggering the redox-sensitive signaling pathway to alleviate oxidative stress in vivo. In recent years, the exploitation of more efficient, safer, and sustainable extraction techniques for natural antioxidants from fruits, vegetables, herbs, and agro-industrial by-products has attracted particular interest.

The present Special Issue, "Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity", aims to collect and to publish original research papers and reviews which covers recent advances of extraction and separation procedures, including optimization of conventional extraction, ultrasound-assisted extraction, microwave-assisted extraction, enzymatic-assisted extraction, subcritical water extraction, pressurized liquid extraction, deep eutectic solvent extraction, or aqueous two-phase system separation. Innovative processing strategies to recover natural antioxidants with improved nutritional and biological activities are particularly welcome. Prior to the bioactivities evaluation of plant extracts with complex mixtures of natural compounds, quantitative and qualitative analyses are encouraged using analytical methodologies, such as HPLC, HPLC–MS, GC-MS, and NMR. In addition, we cordially invite authors to submit their findings regarding the structure-activity relationship investigation and mechanisms of action elucidation of natural antioxidants.

Topics include but are not limited to:

  • Green and novel techniques for the extraction and purification processes of natural antioxidants;
  • Chemical profiling and biological activities screening of natural antioxidants;
  • Investigating the structure-activity relationship of natural antioxidants;
  • Exploring mechanisms of action of natural antioxidants.

Dr. Lijun Zhou
Dr. Shiling Feng
Guest Editors

Manuscript Submission Information

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. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short 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 thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. 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

  • natural antioxidants
  • extraction and purification
  • deep eutectic solvents
  • aqueous two-phase system
  • polyphenols
  • bioactive polysaccharides
  • free radical scavenging
  • stress resistance
  • anti-aging effect

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Related Special Issue

Published Papers (7 papers)

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Research

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18 pages, 2971 KiB  
Article
Bioactive Ingredients in K. pinnata Extract and Synergistic Effects of Combined K. pinnata and Metformin Preparations on Antioxidant Activities in Diabetic and Non-Diabetic Skeletal Muscle Cells
by Pedro Ramon, Daniela Bergmann, Hussain Abdulla, Jean Sparks and Felix Omoruyi
Int. J. Mol. Sci. 2023, 24(7), 6211; https://doi.org/10.3390/ijms24076211 - 25 Mar 2023
Cited by 9 | Viewed by 2192
Abstract
With healthcare costs rising, many affected by ailments are turning to alternative medicine for treatment. More people are choosing to complement their pharmacological regimen with dietary supplements from natural products. In this study, the compound composition of Kalanchoe Pinnata (K. pinnata) and [...] Read more.
With healthcare costs rising, many affected by ailments are turning to alternative medicine for treatment. More people are choosing to complement their pharmacological regimen with dietary supplements from natural products. In this study, the compound composition of Kalanchoe Pinnata (K. pinnata) and the effects of combined preparations of K. pinnata and metformin on antioxidant activity in human skeletal muscle myoblasts (HSMMs) and human diabetic skeletal muscle myoblasts (DHSMMs) were investigated. Ultraperformance liquid chromatography fusion orbitrap mass spectrometry (UPLC-OT-FTMS) identified biologically active flavanols in K. pinnata. The main compounds identified in locally grown K. pinnata were quercetin, kaempferol, apigenin, epigallocatechin gallate (EGCG), and avicularin. Antioxidant results indicated that a combinatorial preparation of K. pinnata with metformin may modulate antioxidant responses by increasing the enzymatic activity of superoxide dismutase and increasing levels of reduced glutathione. A combination of 50 μM and 150 μg/mL of metformin and K. pinnata, respectively, resulted in a significant increase in reduced glutathione levels in non-diabetic and diabetic human skeletal muscle myoblasts and H2O2-stress-induced human skeletal muscle myoblasts. Additionally, a K. pinnata treatment (400 µg/mL) alone significantly increased catalase (CAT) activity for non-diabetic and diabetic human skeletal muscle myoblasts and a H2O2-stress-induced human skeletal muscle myoblast cell line, while significantly lowering malondialdehyde (MDA) levels. However, the treatment options were more effective at promoting cell viability after 24 h versus 72 h and did not promote cell viability after 72 h in H2O2-stress-induced HSMM cells. These treatment options show promise for treating oxidative-stress-mediated pathophysiological complications associated with type II diabetes. Full article
(This article belongs to the Special Issue Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity)
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17 pages, 3861 KiB  
Article
Extraction, Structural, and Antioxidant Properties of Oligosaccharides Hydrolyzed from Panax notoginseng by Ultrasonic-Assisted Fenton Degradation
by Xiaoyan Xu, Guanfeng Deng, Xiao Li, Pingjin Li, Tao Chen, Lijun Zhou, Yan Huang, Ming Yuan, Chunbang Ding and Shiling Feng
Int. J. Mol. Sci. 2023, 24(5), 4506; https://doi.org/10.3390/ijms24054506 - 24 Feb 2023
Cited by 10 | Viewed by 2095
Abstract
Plant polysaccharides exhibit many biological activities that are remarkably affected by molecular size and structures. This study aimed to investigate the degradation effect of ultrasonic-assisted Fenton reaction on the Panax notoginseng polysaccharide (PP). PP and its three degradation products (PP3, PP5, and PP7) [...] Read more.
Plant polysaccharides exhibit many biological activities that are remarkably affected by molecular size and structures. This study aimed to investigate the degradation effect of ultrasonic-assisted Fenton reaction on the Panax notoginseng polysaccharide (PP). PP and its three degradation products (PP3, PP5, and PP7) were obtained from optimized hot water extraction and different Fenton reaction treatments, respectively. The results showed that the molecular weight (Mw) of the degraded fractions significantly decreased after treatment with the Fenton reaction. But the backbone characteristics and conformational structure were similar between PP and PP-degraded products, which was estimated by comparing monosaccharides composition, functional group signals in FT-IR spectra, X-ray differential patterns, and proton signals in 1H NMR. In addition, PP7, with an Mw of 5.89 kDa, exhibited stronger antioxidant activities in both the chemiluminescence-based and HHL5 cell-based methods. The results indicated that ultrasonic-assisted Fenton degradation might be used to improve the biological activities of natural polysaccharides by adjusting the molecular size. Full article
(This article belongs to the Special Issue Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity)
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19 pages, 2845 KiB  
Article
Antioxidant, Tyrosinase, α-Glucosidase, and Elastase Enzyme Inhibition Activities of Optimized Unripe Ajwa Date Pulp (Phoenix dactylifera) Extracts by Response Surface Methodology
by Fanar Alshammari, Md Badrul Alam, Bo-Rim Song and Sang-Han Lee
Int. J. Mol. Sci. 2023, 24(4), 3396; https://doi.org/10.3390/ijms24043396 - 8 Feb 2023
Cited by 5 | Viewed by 2608
Abstract
The Ajwa date (Phoenix dactylifera L., Arecaceae family) is a popular edible fruit consumed all over the world. The profiling of the polyphenolic compounds of optimized unripe Ajwa date pulp (URADP) extracts is scarce. The aim of this study was to extract [...] Read more.
The Ajwa date (Phoenix dactylifera L., Arecaceae family) is a popular edible fruit consumed all over the world. The profiling of the polyphenolic compounds of optimized unripe Ajwa date pulp (URADP) extracts is scarce. The aim of this study was to extract polyphenols from URADP as effectively as possible by using response surface methodology (RSM). A central composite design (CCD) was used to optimize the extraction conditions with respect to ethanol concentration, extraction time, and temperature and to achieve the maximum amount of polyphenolic compounds. High-resolution mass spectrometry was used to identify the URADP’s polyphenolic compounds. The DPPH-, ABTS-radical scavenging, α-glucosidase, elastase and tyrosinase enzyme inhibition of optimized extracts of URADP was also evaluated. According to RSM, the highest amounts of TPC (24.25 ± 1.02 mgGAE/g) and TFC (23.98 ± 0.65 mgCAE/g) were obtained at 52% ethanol, 81 min time, and 63 °C. Seventy (70) secondary metabolites, including phenolic, flavonoids, fatty acids, and sugar, were discovered using high-resolution mass spectrometry. In addition, twelve (12) new phytoconstituents were identified for the first time in this plant. Optimized URADP extract showed inhibition of DPPH-radical (IC50 = 87.56 mg/mL), ABTS-radical (IC50 = 172.36 mg/mL), α-glucosidase (IC50 = 221.59 mg/mL), elastase (IC50 = 372.25 mg/mL) and tyrosinase (IC50 = 59.53 mg/mL) enzymes. The results revealed a significant amount of phytoconstituents, making it an excellent contender for the pharmaceutical and food industries. Full article
(This article belongs to the Special Issue Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity)
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17 pages, 6545 KiB  
Article
Unveiling the Potentiality of Shikonin Derivatives Inhibiting SARS-CoV-2 Main Protease by Molecular Dynamic Simulation Studies
by Raju Das, Sarmin Ummey Habiba, Raju Dash, Yohan Seo and Joohan Woo
Int. J. Mol. Sci. 2023, 24(4), 3100; https://doi.org/10.3390/ijms24043100 - 4 Feb 2023
Cited by 7 | Viewed by 2802
Abstract
Shikonin, a phytochemical present in the roots of Lithospermum erythrorhizon, is well-known for its broad-spectrum activity against cancer, oxidative stress, inflammation, viruses, and anti-COVID-19 agents. A recent report based on a crystallographic study revealed a distinct conformation of shikonin binding to the SARS-CoV-2 [...] Read more.
Shikonin, a phytochemical present in the roots of Lithospermum erythrorhizon, is well-known for its broad-spectrum activity against cancer, oxidative stress, inflammation, viruses, and anti-COVID-19 agents. A recent report based on a crystallographic study revealed a distinct conformation of shikonin binding to the SARS-CoV-2 main protease (Mpro), suggesting the possibility of designing potential inhibitors based on shikonin derivatives. The present study aimed to identify potential shikonin derivatives targeting the Mpro of COVID-19 by using molecular docking and molecular dynamics simulations. A total of 20 shikonin derivatives were screened, of which few derivatives showed higher binding affinity than shikonin. Following the MM-GBSA binding energy calculations using the docked structures, four derivatives were retained with the highest binding energy and subjected to molecular dynamics simulation. Molecular dynamics simulation studies suggested that alpha-methyl-n-butyl shikonin, beta-hydroxyisovaleryl shikonin, and lithospermidin-B interacted with two conserved residues, His41 and Cys145, through multiple bonding in the catalytic sites. This suggests that these residues may effectively suppress SARS-CoV-2 progression by inhibiting Mpro. Taken together, the present in silico study concluded that shikonin derivatives may play an influential role in Mpro inhibition. Full article
(This article belongs to the Special Issue Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity)
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15 pages, 1624 KiB  
Article
The Influence of Solid and Liquid Systems In Vitro on the Growth and Biosynthetic Characteristics of Microshoot Culture of Spiraea betulifolia ssp. aemiliana
by Tatiana V. Zheleznichenko, Dinara S. Muraseva, Andrey S. Erst, Alexander A. Kuznetsov, Maxim S. Kulikovskiy and Vera A. Kostikova
Int. J. Mol. Sci. 2023, 24(3), 2362; https://doi.org/10.3390/ijms24032362 - 25 Jan 2023
Cited by 5 | Viewed by 1937
Abstract
The paper focuses on the growth dynamics and biosynthetic characteristics of the microshoot culture of Spiraea betulifolia ssp. aemiliana obtained in vitro in agar-solidified and liquid media. Microshoots cultured in either type of media showed similar growth dynamics. The most active culture growth [...] Read more.
The paper focuses on the growth dynamics and biosynthetic characteristics of the microshoot culture of Spiraea betulifolia ssp. aemiliana obtained in vitro in agar-solidified and liquid media. Microshoots cultured in either type of media showed similar growth dynamics. The most active culture growth was observed from day 35 to day 60. A comparative analysis of the contents of flavonoids and phenol carboxylic acids showed a higher level of phenol carboxylic acids (5.3–6.84%) and a stronger 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical–scavenging activity (half-maximal inhibitory concentration: 341 µg/mL) in S. betulifolia ssp. aemiliana microshoots grown in the liquid medium compared to the microshoots cultured in the solid medium. The flavonoid content of the cultured microshoot did not depend on the consistency of the medium. High-performance liquid chromatography (HPLC) was employed to study the profile and levels of phenolic compounds in microshoots, intact plants, and ex vitro–acclimated S. betulifolia ssp. aemiliana plants. The concentration of kaempferol glycosides was found to be higher in microshoots (1.33% in the solid medium, 1.06% in the liquid medium) compared to intact plants and ex vitro–acclimated plants. Thus, the microshoots of S. betulifolia ssp. aemiliana cultured in the liquid medium rapidly increase their biomass and are an inexpensive promising source of biologically active antioxidant substances, mainly phenol carboxylic acids and kaempferol glycosides. Full article
(This article belongs to the Special Issue Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity)
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13 pages, 2701 KiB  
Article
Coordination of AMPK and YAP by Spatholobi Caulis and Procyanidin B2 Provides Antioxidant Effects In Vitro and In Vivo
by Su-Jin Bae, Seon Been Bak and Young Woo Kim
Int. J. Mol. Sci. 2022, 23(22), 13730; https://doi.org/10.3390/ijms232213730 - 8 Nov 2022
Cited by 5 | Viewed by 2199
Abstract
The liver is vulnerable to oxidative attacks from heavy metals, such as iron, as well as some drugs, including acetaminophen. It has been shown that enhanced oxidative stress in the liver leads to excessive ROS production and mitochondrial dysfunction, resulting in organ injury. [...] Read more.
The liver is vulnerable to oxidative attacks from heavy metals, such as iron, as well as some drugs, including acetaminophen. It has been shown that enhanced oxidative stress in the liver leads to excessive ROS production and mitochondrial dysfunction, resulting in organ injury. The beneficial effects of Spatholobi Caulis (SC), a natural herbal medicine, include treating ischemic stroke, inhibiting tumor cell invasion, pro-angiogenic activities, and anti-inflammatory properties. Scientific studies on its effects against hepatotoxic reagents (e.g., iron and acetaminophen), as well as their underlying mechanisms, are insufficient. This study examined the antioxidant effects and mechanisms of SC in vitro and in vivo. In cells, the proinflammatory mediator, arachidonic acid (AA), plus iron, significantly induced an increase in ROS generation, the damage in mitochondrial membrane potential, and the resulting apoptosis, which were markedly blocked by SC. More importantly, SC affected the activation of AMP-activated protein kinase (AMPK)-related proteins, which were vital to regulating oxidative stress in cells. In addition, SC mediated the expression of Yes-associated protein (YAP)-related proteins. Among the active compounds in SC, the procyanidin B2, but not liquiritigenin, daidzein, and genistein, significantly inhibited the cytotoxicity induced by AA + iron, and activated the LKB1-AMPK pathway. In mice, the oral administration of SC alleviated the elevations of ALT and histological changes by the acetaminophen-induced liver injury. These results reveal the potential of SC and a key bioactive component, procyanidin B2, as antioxidant candidates for hepatoprotection. Full article
(This article belongs to the Special Issue Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity)
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Review

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25 pages, 444 KiB  
Review
New Insights of Biological Functions of Natural Polyphenols in Inflammatory Intestinal Diseases
by Yunchang Zhang, Tianqi Mu, Xiong Deng, Ruiting Guo, Bing Xia, Linshu Jiang, Zhenlong Wu and Ming Liu
Int. J. Mol. Sci. 2023, 24(11), 9581; https://doi.org/10.3390/ijms24119581 - 31 May 2023
Cited by 8 | Viewed by 2430
Abstract
The intestine is critically crucial for nutrient absorption and host defense against exogenous stimuli. Inflammation-related intestinal diseases, including enteritis, inflammatory bowel disease (IBD), and colorectal cancer (CRC), are heavy burdens for human beings due to their high incidence and devastating clinical symptoms. Current [...] Read more.
The intestine is critically crucial for nutrient absorption and host defense against exogenous stimuli. Inflammation-related intestinal diseases, including enteritis, inflammatory bowel disease (IBD), and colorectal cancer (CRC), are heavy burdens for human beings due to their high incidence and devastating clinical symptoms. Current studies have confirmed that inflammatory responses, along with oxidative stress and dysbiosis as critical pathogenesis, are involved in most intestinal diseases. Polyphenols are secondary metabolites derived from plants, which possess convincible anti-oxidative and anti-inflammatory properties, as well as regulation of intestinal microbiome, indicating the potential applications in enterocolitis and CRC. Actually, accumulating studies based on the biological functions of polyphenols have been performed to investigate the functional roles and underlying mechanisms over the last few decades. Based on the mounting evidence of literature, the objective of this review is to outline the current research progress regarding the category, biological functions, and metabolism of polyphenols within the intestine, as well as applications for the prevention and treatment of intestinal diseases, which might provide ever-expanding new insights for the utilization of natural polyphenols. Full article
(This article belongs to the Special Issue Natural Antioxidants: Extraction, Optimization, Characterization, and Their Biological Activity)
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