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Extraction and Characterization of Natural Bioactive Compounds

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A special issue of Antioxidants (ISSN 2076-3921). This special issue belongs to the section "Extraction and Industrial Applications of Antioxidants".

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 16195

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Dr. Susana M. Cardoso

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LAQV-REQUIMTE, Department of Chemistry, Universidade de Aveiro, 3810-193 Aveiro, Portugal
Interests: natural products; structural analysis; nutrients and bioactive compounds; liquid chromatography; mass spectrometry; antioxidant; bioactivity; bioaccessibility and bioavailability; added-value products
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Dr. Dulcineia F. Wessel

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School of Agriculture, Polytechnic Institute of Viseu, Quinta da Alagoa—Estrada de Nelas, Ranhados, 3500-606 Viseu, Portugal
Interests: phytopreparations to support health; botanical materials with biological activity; food product development from plant biomass; nutritional and sensory attributes; food industry and agricultural by-products
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Dr. Marcelo D. Catarino

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LAQV-REQUIMTE & Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: seaweeds; natural compounds; polyphenols; bioactive properties; bioavailability and metabolism
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nature has inexhaustibly provided health solutions for thousands of years. Traditional medicine, based on the use of biologically active natural products, continues to be the first choice of the world's population for primary health services, and the pillar for the discovery and development of new drugs and active principles with potential applications in various fields, including cosmetics, food, textiles, agriculture, and biotechnology, among others. As such, even if many natural sources have been examined before, there is still much more of the world's biodiversity, including plants, animals, and microorganisms, that needs to be uncovered.

Traditionally, the discovery of natural bioactive compounds starts with the extraction process, followed by the purification, isolation, and elucidation of the structure of biomolecules, along with the screening of their bioactivities and ultimately the elucidation of structure–activity relationships. Implicit methodologies make this scheme extremely laborious and challenging, although recent technological and scientific developments have enabled the use of new strategies, revitalizing the search for bioactive compounds from natural resources.

This Special Issue invites original research and review articles covering different aspects related to natural bioactive compounds, including (but not limited to) advances on extraction, purification, and characterization techniques; chemistry and structural elucidation; biological activities; and mechanisms of action of extracts, purified fractions, isolated compounds, and/or novel value-added products.

We are eager to receive your contributions.

Dr. Susana M. Cardoso
Dr. Dulcineia F. Wessel
Dr. Marcelo D. Catarino
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. Antioxidants is an international peer-reviewed open access monthly 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 2900 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

analytical techniques
bioactive compounds
extraction
natural products
structure analysis
structure–activity relationship

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Published Papers (8 papers)

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Research

20 pages, 1579 KiB

Open AccessArticle

Fractionation of High-Value Compounds from Hops Using an Optimised Sequential Extraction Procedure

by Ana I. Paniagua-García, David Ruano-Rosa and Rebeca Díez-Antolínez

Antioxidants 2024, 13(1), 45; https://doi.org/10.3390/antiox13010045 - 26 Dec 2023

Cited by 2 | Viewed by 1591

Abstract

This study describes the development and optimisation of a process for the extraction and fractionation of high-value compounds from hops. Firstly, the efficacy of ten organic solvents was compared for performing the initial solid–liquid extraction of compounds from hop pellets with subsequent fractionation steps. A methanol–dichloromethane mixture was selected and the extraction variables were optimised in order to maximise the recovery of valuable hop compounds separated into different streams (α- and β-acids in soft resins, xanthohumol in hard resins, and phenolics in spent solids) after fractionation steps. The optimisation results showed that extraction of hop pellets performed at room temperature with 19.7% (v/v) methanol for 89 min yielded recoveries of 86.57% α-acids and 89.14% β-acids in soft resins, 78.48% xanthohumol in hard resins and 67.10% phenolics in spent solids. These conditions were successfully validated using six hop varieties. Moreover, the antioxidant properties of all recovered fractions were compared and the soft resins showed the highest antioxidant activities, reaching values of 3.91 ± 0.10 g AAE/100 g for ferric reducing power (FRAP) and 0.10 ± 0.01 mg/mL for 50% of radical scavenging activity (EC50). The optimised sequential extraction could serve as a basis for larger scale-up for industrial production. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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19 pages, 2350 KiB

Open AccessArticle

Stability of Flavan-3-ols, Theaflavins, and Methylxanthines in 30 Industrial Green, Black, and White Tea (Camellia sinensis L.) Extracts Characterized via Liquid Chromatography Techniques

by Antonio M. Inarejos-Garcia, Julia Heil, Sonia Guilera Bermell and Gertrud E. Morlock

Antioxidants 2023, 12(12), 2121; https://doi.org/10.3390/antiox12122121 - 15 Dec 2023

Cited by 1 | Viewed by 1312

Abstract

Commercially available tea extracts for dietary supplements and nutraceuticals are standardized to characteristic components of Camellia sinensis L., such as epigallocatechin gallate (EGCG) and total catechins or polyphenols. However, since most commercial tea extracts are highly concentrated into only one molecule such as EGCG, the comparatively less stable catechin, the oxidative stability of the extract during the 24-month shelf life was questioned. It was hypothesized that the overall oxidative stability is reduced for highly purified/concentrated tea extracts due to the absence of other natural antioxidants stabilizing the complex mixture. Via liquid chromatographic analysis, the individual chromatographic profiles of 30 commercial white, green, and black tea extracts were evaluated and compared regarding oxidative stability and functional properties. The contents of bioactive flavan-3-ols, theaflavins, and methylxanthines differed much from what was claimed by the suppliers. At the end of the product shelf life, most of the commercial green and black tea extracts showed a decrease in the flavan-3-ol content, the main bioactive components of tea. A high EGCG content to the detriment of other possibly stabilizing flavan-3-ols or antioxidants in tea was found to explain the lower oxidative stability of such tea extract products. A natural overall composition of molecular structures was found to be superior to a strong enrichment in just one molecule. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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25 pages, 2139 KiB

Open AccessArticle

Valorization of Defatted Cherry Seed Residues from Liquor Processing by Matrix Solid-Phase Dispersion Extraction: A Sustainable Strategy for Production of Phenolic-Rich Extracts with Antioxidant Potential

by Sandra Rodríguez-Blázquez, Lorena Fernández-Ávila, Esther Gómez-Mejía, Noelia Rosales-Conrado, María Eugenia León-González and Rubén Miranda

Antioxidants 2023, 12(12), 2041; https://doi.org/10.3390/antiox12122041 - 24 Nov 2023

Cited by 3 | Viewed by 1485

Abstract

The integrated valorization of food chain waste is one of the most promising alternatives in the transition to a sustainable bioeconomy. Thus, an efficient solid-phase matrix dispersion extraction method, using experimental factorial design and response surface methodology, has been developed and optimized for the recovery of polyphenols from defatted cherry seeds obtained after cherry liquor manufacture and subsequent fatty acid extraction, evaluating the effect of each processing step on the composition and phenolic content of sweet cherry residues. The phenolic extracts before fermentation showed the highest content of total polyphenols (TPC) and flavonoids (TFC) (3 ± 1 mg QE·g⁻¹ and 1.37 ± 0.08 mg GAE·g⁻¹, respectively), while the highest antioxidant capacity was obtained in the defatted seed extracts after both fermentation and distillation. In addition, high-performance liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (HPLC-ESI-QTOF-MS) was used to determine the phenolic profile. Dihydroxybenzoic acid, neochlorogenic acid, caffeic acid, and quercetin were the main phenolics found, showing differences in concentration between the stages of liquor production. The results underline the prospective of cherry by-products for obtaining phenol-rich bioactive extracts for possible use in different industrial sectors, offering a feasible solution for the cascade valorization of cherry agri-food waste. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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18 pages, 1850 KiB

Open AccessArticle

New Megastigmane and Polyphenolic Components of Henna Leaves and Their Tumor-Specific Cytotoxicity on Human Oral Squamous Carcinoma Cell Lines

by Mohamed A. A. Orabi, Esam A. Orabi, Ahmed Abdullah Al Awadh, Mohammed Merae Alshahrani, Basel A. Abdel-Wahab, Hiroshi Sakagami and Tsutomu Hatano

Antioxidants 2023, 12(11), 1951; https://doi.org/10.3390/antiox12111951 - 1 Nov 2023

Cited by 2 | Viewed by 1740

Abstract

Polyphenols have a variety of phenolic hydroxyl and carbonyl functionalities that enable them to scavenge many oxidants, thereby preserving the human redox balance and preventing a number of oxidative stress-related chronic degenerative diseases. In our ongoing investigation of polyphenol-rich plants in search of novel molecules, we resumed the investigation of Lawsonia inermis L. (Lythraceae) or henna, a popular ancient plant with aesthetic and therapeutic benefits. The leaves’ 70% aq acetone extract was fractionated on a Diaion HP-20 column with different ratios of H₂O/an organic solvent. Multistep gel chromatographic fractionation and HPLC purification of the Diaion 75% aq MeOH and MeOH fractions led to a new compound (1) along with tannin-related metabolites, benzoic acid (2), benzyl 6′-O-galloyl-β-D-glucopyranoside (3), and ellagic acid (4), which are first isolated from henna. Repeating the procedures on the Diaion 50% aq MeOH eluate led to the first-time isolation of two O-glucosidic ellagitannins, heterophylliin A (5), and gemin D (6), in addition to four known C-glycosidic ellagitannins, lythracin D (7), pedunculagin (8), flosin B (9), and lagerstroemin (10). The compound structures were determined through intensive spectroscopic investigations, including HRESIMS, 1D (¹H and ¹³C) and 2D (¹H–¹H COSY, HSQC, HMBC, and NOESY) NMR, UV, [α]_D, and CD experiments. The new structure of 1 was determined to be a megastigmane glucoside gallate; its biosynthesis from gallic acid and a β-ionone, a degradative product of the common metabolite β-carotin, was highlighted. Cytotoxicity investigations of the abundant ellagitannins revealed that lythracin D2 (7) and pedunculagin (8) are obviously more cytotoxic (tumor specificity = 2.3 and 2.8, respectively) toward oral squamous cell carcinoma cell lines (HSC-2, HSC-4, and Ca9-22) than normal human oral cells (HGF, HPC, and HPLF). In summary, Lawsonia inermis is a rich source of anti-oral cancer ellagitannins. Also, the several discovered polyphenolics highlighted here emphasize the numerous biological benefits of henna and encourage further clinical studies to profit from their antioxidant properties against oxidative stress-related disorders. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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21 pages, 2779 KiB

Open AccessArticle

Biological Activity and Metabolomics of Griffonia simplicifolia Seeds Extracted with Different Methodologies

by Giuseppe Mannino, Graziella Serio, Raimondo Gaglio, Massimo E. Maffei, Luca Settanni, Vita Di Stefano and Carla Gentile

Antioxidants 2023, 12(9), 1709; https://doi.org/10.3390/antiox12091709 - 1 Sep 2023

Cited by 2 | Viewed by 2251

Abstract

Griffonia simplicifolia, a tropical plant endemic to West Africa, is highly regarded for its significant pharmacological potential. The objective of this study was to evaluate the metabolomic profile and to explore the antioxidant properties, antiproliferative activity, and antimicrobial potential of G. simplicifolia seed extracts obtained through either maceration, microwave-assisted extraction (MAE), or Soxhlet extraction using water, acetone, methanol and ethanol as solvents. Overall, methanol possessed superior total extraction efficiency. HPLC analyses confirmed the efficacy of acetone and ethanol as optimal solvents for the extraction of flavonoids and flavan-3-ols, whereas MAE exhibited enhanced effectiveness in extracting N-containing compounds, including 5-hydroxytryptophan (5-HTP). HPLC-MS analyses identified forty-three compounds, including thirty-four phenolic compounds and nine N-containing molecules. Isomyricitrin, taxifolin and a flavonol glucuronide were the main polyphenols, whereas 5-HTP was the main N-containing compound. Hydroalcoholic G. simplicifolia extracts showed the highest radical scavenging and metal-reducing antioxidant power, suggesting that most of the contribution to antioxidant activity depends on the more polar bioactive compounds. G. simplicifolia extracts showed dose-dependent antiproliferative activity against three distinct cancer cell lines (HeLa, HepG2, and MCF-7), with notable variations observed among both the different extracts and cell lines and divergent GI₅₀ values, emphasizing substantial discrepancies in cell sensitivity to the various extracts. Furthermore, G. simplicifolia extracts revealed antibiotic activity against Staphylococcus aureus. Our results highlight the potential of G. simplicifolia phytochemicals in the development of functional foods, nutraceuticals, and dietary supplements. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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21 pages, 5452 KiB

Open AccessArticle

Metabolites Profiling and Bioassays Reveal Bassia indica Ethanol Extract Protective Effect against Stomach Ulcers Development via HMGB1/TLR-4/NF-κB Pathway

by Zeinab A. El-Gendy, Rehab F. Taher, Abdelbaset M. Elgamal, Ahmed Serag, Azza Hassan, Gehad A. Abdel Jaleel, Mohamed A. Farag and Abdelsamed I. Elshamy

Antioxidants 2023, 12(6), 1263; https://doi.org/10.3390/antiox12061263 - 12 Jun 2023

Cited by 3 | Viewed by 1904

Abstract

Clinical manifestation of gastric ulcers is frequent, in addition to their costly drug regimens, warranting the development of novel drugs at lower costs. Although Bassia indica is well characterized for its anti-inflammatory and antioxidant potential, capacity of its ethanol extract (BIEE) to prevent stomach ulcers’ progression has not been reported. A nuclear protein termed high-mobility group box 1 (HMGB1) plays a key role in the formation of stomach ulcers by triggering a number of inflammatory responses. The main purpose of the current investigation was to evaluate the in vivo anti-inflammatory and anti-ulcerogenic capabilities of BIEE against ethanol-induced gastric ulcers in rats via the HMGB1/TLR-4/NF-B signaling pathway. HMGB1 and Nuclear factor kappa (NF-B) expression, IL-1β and Nrf2 contents showed an increase along with ulcer development, concurrent with an increase in immunohistochemical TLR-4 level. In contrast, pre-treatment with BIEE significantly reduced HMGB1 and Nuclear factor kappa (NF-B) expression levels, IL-1β and Nrf2 contents and ulcer index value. Such protective action was further confirmed based on histological and immunohistochemical TLR-4 assays. Untargeted analysis via UPLC-ESI–Qtof-MS has allowed for the comprehensive characterization of 40 metabolites in BIEE mostly belonged to two main chemical classes, viz., flavonoids and lipids. These key metabolites, particularly flavonoids, suggesting a mediation for the anti-inflammatory and anti-ulcerogenic properties of BIEE, pose it as a promising natural drug regimen for treatment of stomach ulcers. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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15 pages, 2158 KiB

Open AccessArticle

Up-Regulation of the Nrf2/HO-1 Antioxidant Pathway in Macrophages by an Extract from a New Halophilic Archaea Isolated in Odiel Saltworks

by Javier Ávila-Román, Patricia Gómez-Villegas, Carla C. C. R. de Carvalho, Javier Vigara, Virginia Motilva, Rosa León and Elena Talero

Antioxidants 2023, 12(5), 1080; https://doi.org/10.3390/antiox12051080 - 11 May 2023

Cited by 7 | Viewed by 2510

Abstract

The production of reactive oxygen species (ROS) plays an important role in the progression of many inflammatory diseases. The search for antioxidants with the ability for scavenging free radicals from the body cells that reduce oxidative damage is essential to prevent and treat these pathologies. Haloarchaea are extremely halophilic microorganisms that inhabit hypersaline environments, such as saltworks or salt lakes, where they have to tolerate high salinity, and elevated ultraviolet (UV) and infrared radiations. To cope with these extreme conditions, haloarchaea have developed singular mechanisms to maintain an osmotic balance with the medium, and are endowed with unique compounds, not found in other species, with bioactive properties that have not been fully explored. This study aims to assess the potential of haloarchaea as a new source of natural antioxidant and anti-inflammatory agents. A carotenoid-producing haloarchaea was isolated from Odiel Saltworks (OS) and identified on the basis of its 16S rRNA coding gene sequence as a new strain belonging to the genus Haloarcula. The Haloarcula sp. OS acetone extract (HAE) obtained from the biomass contained bacterioruberin and mainly C18 fatty acids, and showed potent antioxidant capacity using ABTS assay. This study further demonstrates, for the first time, that pretreatment with HAE of lipopolysaccharide (LPS)-stimulated macrophages results in a reduction in ROS production, a decrease in the pro-inflammatory cytokines TNF-α and IL-6 levels, and up-regulation of the factor Nrf2 and its target gene heme oxygenase-1 (HO-1), supporting the potential of the HAE as a therapeutic agent in the treatment of oxidative stress-related inflammatory diseases. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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11 pages, 1425 KiB

Open AccessArticle

Cydonia oblonga Mill. Pulp Callus Inhibits Oxidative Stress and Inflammation in Injured Cells

by Federica Gubitosa, Daniele Fraternale, Roberta De Bellis, Andrea Gorassini, Leila Benayada, Laura Chiarantini, Maria Cristina Albertini and Lucia Potenza

Antioxidants 2023, 12(5), 1076; https://doi.org/10.3390/antiox12051076 - 10 May 2023

Cited by 4 | Viewed by 2212

Abstract

The pharmacological activity of a callus extract from the pulp of Cydonia oblonga Mill., also known as quince, was investigated in murine macrophage (RAW 264.7) and human keratinocyte (HaCaT) cell lines. In particular, the anti-inflammatory activity of C. oblonga Mill. pulp callus extract was assessed in lipopolysaccharides (LPS)-treated RAW 264.7 by the Griess test and in LPS-treated HaCaT human keratinocytes by examining the expression of genes involved in the inflammatory process, including nitric oxide synthase (iNOS), interleukin-6 (IL-6), interleukin-1β (IL-1β), nuclear factor-kappa-B inhibitor alfa (ikBα), and intercellular adhesion molecule (ICAM). The antioxidant activity was evaluated by quantizing the reactive oxygen species (ROS) production in the hydrogen peroxide and tert-butyl hydroperoxide-injured HaCaT cell line. The obtained results indicate that C. oblonga callus from fruit pulp extract has anti-inflammatory and antioxidant activities, suggesting its possible application in delaying and preventing acute or chronic diseases associated with aging or in the treatment of wound dressing. Full article

(This article belongs to the Special Issue Extraction and Characterization of Natural Bioactive Compounds)

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