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

Deadline for manuscript submissions: closed (28 June 2021) | Viewed by 26465

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Special Issue Editors

Prof. Dr. Marcello Iriti

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Department of Biomedical, Surgical and Dental Sciences, Università degli Studi di Milano, 20133 Milan, Italy
Interests: essential oils; bioactive phytochemicals; ethnopharmacology; antimicrobial resistance; one health; food security
Special Issues, Collections and Topics in MDPI journals

Dr. Elena Varoni

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Department of Biomedical, Surgical and Dental Sciences, Università degli Studi di Milano, Milan, Italy
Interests: oral medicine; biomaterials; nutrition; oral health
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Dr. Sara Vitalini

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Guest Editor

Department of Agricultural and Environmental Sciences, Università degli Studi di Milano, Milan, Italy
Interests: crop protection; plant diseases; bioactivity; phytochemistry; ethnopharmacology; natural products
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Special Issue Information

Dear Colleagues,

Flavonoids are the largest group of polyphenols, plant secondary metabolites arising from the essential aromatic amino acid phenylalanine (or more rarely from tyrosine) via the phenylpropanoid pathway. The flavan nucleus is the basic 15-carbon skeleton of flavonoids (C6-C3-C6), which consists of two phenyl rings (A and B) and a heterocyclic ring (C). The main classes of flavonoids (flavonols, flavanols, flavones, flavanones, isoflavones and anthocyanidins) differ in the level of oxidation and saturation of the C ring, while individual compounds within a class vary in the substitution pattern of the A and B rings. In planta, they exert a plethora of ecological roles as variously colored pigments and signaling molecules, being involved in pollinator attraction and root symbioses, just to name a few examples. In addition, flavonoids protect plant from abiotic and biotic stressors, such as UV radiation and pathogen attack (in this context, they represent a group of phytoalexins). Health-promoting effects of traditional food and medicinal plants have been ascribed to their content in bioactive phytochemicals including flavonoids, also known as nutraceuticals. A huge number of in vitro/in vivo studies on animal and cell experimental models highlighted their preclinical efficacy as antioxidant, antimicrobial, anticancer/chemopreventive, antidiabetic, vasoprotective and vasodilating agents, in addition to their cardio- and neuroprotective effects. The flavonoid mechanism of action is directed toward multiple molecular and biochemical targets in prokaryotic and eukaryotic cells. Therefore, plant foods and herbal remedies are multitarget agents containing hundreds of flavonoids (including aglycones and glycosides) and other different phytochemicals. In this context, given the global threat of antimicrobial resistance, these phytotherapeutics have a low risk of selecting chemoresistant microbial and cancer cells. Flavonoids can also reverse chemoresistance (including multidrug resistance) modulating efflux pumps, and hence they can be used as adjuvant (or chemosensitizer) agents in conventional antimicrobial and anticancer therapies. Not least, flavonoids can mitigate age-associated cellular damage and extend lifespan as epigenetic modulators and by mimicking calorie restriction. Finally, oral bioavailability of flavonoids represents another relevant issue. Indeed, after ingestion, they are metabolized by phase I and II enzymes like other xenobiotics before reaching the target cells and tissues.

In this very wide context, we invite investigators to submit both original research and review articles that explore all these aspects.

Prof. Dr. Marcello Iriti
Dr. Elena Maria Varoni
Prof. Dr. Sara Vitalini
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.

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Keywords

Flavonoid biosynthesis
Flavonoid gene expression
Plant abiotic stresses
Plant biotic stresses
Phytoalexins
Chemoecology
Ecophysiology
Functional foods
Medicinal plants & herbal remedies
Nutraceuticals
Antioxidant activity
Antimicrobial activity
Antimicrobial resistance
Anticancer activity
Cancer chemoprevention
Antidiabetic activity
Vasoprotection
Cardioprotection
Neuroprotection
Antiaging agents
Sirtuins
Oral diseases
Oral bioavailability
In human studies & randomized clinical studies

Published Papers (8 papers)

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Research

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18 pages, 1758 KiB

Open AccessArticle

Neuroprotective Properties of Kempferol Derivatives from Maesa membranacea against Oxidative Stress-Induced Cell Damage: An Association with Cathepsin D Inhibition and PI3K/Akt Activation

by Danuta Jantas, Janusz Malarz, Thanh Nguyen Le and Anna Stojakowska

Int. J. Mol. Sci. 2021, 22(19), 10363; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms221910363 - 26 Sep 2021

Cited by 13 | Viewed by 2517

Abstract

As components of the human diet with potential health benefits, flavonols are the subject of numerous studies, confirming their antioxidant, free radical scavenging and anti-inflammatory activity. Taking into consideration the postulated pathogenesis of certain CNS dysfunctions characterized by neuronal degradation, flavonols may prevent the decay of neurons in multiple pathways. Leaves of Maesa membranacea yielded several flavonol glycosides including α-rhamnoisorobin (kaempferol 7-O-α-rhamnoside) and kaempferitrin (kaempferol 3,7-di-O-α-rhamnoside). The latter compound was a major constituent of the investigated plant material. Neuroprotective effects of kaempferitrin and α-rhamnoisorobin were tested in vitro using H₂O₂-, 6-OHDA- and doxorubicin-induced models of SH-SY5Y cell damage. Both undifferentiated and differentiated neuroblastoma cells were used in the experiments. α-Rhamnoisorobin at a concentration range of 1–10 µM demonstrated cytoprotective effects against H₂O₂-induced cell damage. The compound (at 1–10 µM) was also effective in attenuating 6-OHDA-induced neurotoxicity. In both H₂O₂- and 6-OHDA-induced cell damage, kaempferitrin, similar to isoquercitrin, demonstrated neuroprotective activity at the highest of the tested concentrations (50 µM). The tested flavonols were not effective in counteracting doxorubicin-induced cytotoxicity. Their caspase-3- and cathepsin D-inhibitory activities appeared to be structure dependent. Inhibition of the PI3-K/Akt pathway abolished the neuroprotective effect of the investigated flavonols. Full article

(This article belongs to the Special Issue Flavonoids)

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18 pages, 9739 KiB

Open AccessArticle

Photoprotective Role of Photosynthetic and Non-Photosynthetic Pigments in Phillyrea latifolia: Is Their “Antioxidant” Function Prominent in Leaves Exposed to Severe Summer Drought?

by Antonella Gori, Cecilia Brunetti, Luana Beatriz dos Santos Nascimento, Giovanni Marino, Lucia Guidi, Francesco Ferrini, Mauro Centritto, Alessio Fini and Massimiliano Tattini

Int. J. Mol. Sci. 2021, 22(15), 8303; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22158303 - 02 Aug 2021

Cited by 11 | Viewed by 3116

Abstract

Carotenoids and phenylpropanoids play a dual role of limiting and countering photooxidative stress. We hypothesize that their “antioxidant” function is prominent in plants exposed to summer drought, when climatic conditions exacerbate the light stress. To test this, we conducted a field study on Phillyrea latifolia, a Mediterranean evergreen shrub, carrying out daily physiological and biochemical analyses in spring and summer. We also investigated the functional role of the major phenylpropanoids in different leaf tissues. Summer leaves underwent the most severe drought stress concomitantly with a reduction in radiation use efficiency upon being exposed to intense photooxidative stress, particularly during the central hours of the day. In parallel, a significant daily variation in both carotenoids and phenylpropanoids was observed. Our data suggest that the morning-to-midday increase in zeaxanthin derived from the hydroxylation of ß-carotene to sustain non-photochemical quenching and limit lipid peroxidation in thylakoid membranes. We observed substantial spring-to-summer and morning-to-midday increases in quercetin and luteolin derivatives, mostly in the leaf mesophyll. These findings highlight their importance as antioxidants, countering the drought-induced photooxidative stress. We concluded that seasonal and daily changes in photosynthetic and non-photosynthetic pigments may allow P. latifolia leaves to avoid irreversible photodamage and to cope successfully with the Mediterranean harsh climate. Full article

(This article belongs to the Special Issue Flavonoids)

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17 pages, 1441 KiB

Open AccessArticle

Physiological Response of Maize Plants (Zea mays L.) to the Use of the Potassium Quercetin Derivative

by Dagmara Migut, Marta Jańczak-Pieniążek, Tomasz Piechowiak, Jan Buczek and Maciej Balawejder

Int. J. Mol. Sci. 2021, 22(14), 7384; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22147384 - 09 Jul 2021

Cited by 11 | Viewed by 2269

Abstract

Plant production technologies based solely on the improvement of plants themselves face obstacles resulting from the natural limitations of the biological potential of varieties. Therefore, new substances are sought that positively influence the growth and development of plants and increase resistance to various biotic and abiotic stresses, which also translates into an increase in obtained yields. The exogenous application of various phytoprotectants shows great promise in terms of cost effectiveness compared to traditional breeding methods or transgenic approaches in relation to increasing plant tolerance to abiotic stresses. Quercetin is a strong antioxidant among phenolic compounds, and it plays a physiological and biochemical role in plants. As such, the aim of this research was to assess the effect of an aqueous solution of a quercetin derivative with potassium, applied in various concentrations (0.5%, 1.0%, 3.0% and 5.0%), on the efficiency of the photosynthetic apparatus and biochemical properties of maize. Among the tested variants, compared to the control, the most stimulating effect on the course of physiological processes (P_N, g_s, c_i, CCI, F_v/F_m, F_v/F₀, PI) in maize leaves was found in 3.0 and 5.0% aqueous solutions of the quercetin derivative. The highest total antioxidant capacity and total content of polyphenolic compounds were found for plants sprayed with 5.0% quercetin derivative solution; therefore, in this study, the optimal concentration could not be clearly selected. Full article

(This article belongs to the Special Issue Flavonoids)

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14 pages, 1326 KiB

Open AccessArticle

In Vitro Metabolism of Six C-Glycosidic Flavonoids from Passiflora incarnata L.

by Martina Tremmel, Josef Kiermaier and Jörg Heilmann

Int. J. Mol. Sci. 2021, 22(12), 6566; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22126566 - 18 Jun 2021

Cited by 18 | Viewed by 3307

Abstract

Several medical plants, such as Passiflora incarnata L., contain C-glycosylated flavonoids, which may contribute to their efficacy. Information regarding the bioavailability and metabolism of these compounds is essential, but not sufficiently available. Therefore, the metabolism of the C-glycosylated flavones orientin, isoorientin, schaftoside, isoschaftoside, vitexin, and isovitexin was investigated using the Caco-2 cell line as an in vitro intestinal and epithelial metabolism model. Isovitexin, orientin, and isoorientin showed broad ranges of phase I and II metabolites containing hydroxylated, methoxylated, and sulfated compounds, whereas schaftoside, isoschaftoside, and vitexin underwent poor metabolism. All metabolites were identified via UHPLC-MS or UHPLC-MS/MS using compound libraries containing all conceivable metabolites. Some structures were confirmed via UHPLC-MS experiments with reference compounds after a cleavage reaction using glucuronidase and sulfatase. Of particular interest is the observed cleavage of the C–C bonds between sugar and aglycone residues in isovitexin, orientin, and isoorientin, resulting in unexpected glucuronidated or sulfated luteolin and apigenin derivatives. These findings indicate that C-glycosidic flavones can be highly metabolized in the intestine. In particular, flavonoids with ortho-dihydroxy groups showed sulfated metabolites. The identified glucuronidated or sulfated aglycones demonstrate that enzymes expressed by Caco-2 cells are able to potentially cleave C–C bonds in vitro. Full article

(This article belongs to the Special Issue Flavonoids)

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18 pages, 669 KiB

Open AccessArticle

Flavonoid and Phenolic Acids Content and In Vitro Study of the Potential Anti-Aging Properties of Eutrema japonicum (Miq.) Koidz Cultivated in Wasabi Farm Poland

by Katarzyna Szewczyk, Wioleta Pietrzak, Katarzyna Klimek, Małgorzata Miazga-Karska, Agnieszka Firlej, Marek Flisiński and Anna Grzywa-Celińska

Int. J. Mol. Sci. 2021, 22(12), 6219; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22126219 - 09 Jun 2021

Cited by 19 | Viewed by 3922

Abstract

Skin aging is a natural, unavoidable, and complex process caused by oxidative stress. As a consequence, it leads to an increase in the activation of extracellular matrix disruption enzymes and DNA damage. The search for natural sources that inhibit these mechanisms can be a good approach to prevent skin aging. The purpose of our study was to evaluate the composition of flavonoids and phenolic acids in the extracts obtained from the flowers, roots, and leaves of Eutrema japonicum cultivated in Poland. Then, the resultant extracts were subjected to an assessment of antioxidant, anti-collagenase, anti-elastase, anti-hyaluronidase, antibacterial, and cytotoxic properties. It was demonstrated that the extract from the flowers had the highest content of flavonoid glycosides (17.15 mg/g DE). This extract showed the greatest antioxidant, anti-collagenase, anti-elastase, and anti-hyaluronidase activities compared to the other samples. Importantly, the collagenase inhibitory activity of this extract (93.34% ± 0.77%) was better than that of positive control epigallocatechin gallate (88.49% ± 0.45%). An undeniable advantage of this extract was also to possess moderate antibacterial properties and no cytotoxicity towards normal human skin fibroblasts. Our results suggest that extracts from E. japonicum flowers may be considered as a promising antiaging compound for applications in cosmetic formulations. Full article

(This article belongs to the Special Issue Flavonoids)

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13 pages, 2922 KiB

Open AccessArticle

Anti-Platelet Properties of Phenolic and Nonpolar Fractions Isolated from Various Organs of Elaeagnus rhamnoides (L.) A. Nelson in Whole Blood

by Bartosz Skalski, Joanna Rywaniak, Aleksandra Szustka, Jerzy Żuchowski, Anna Stochmal and Beata Olas

Int. J. Mol. Sci. 2021, 22(6), 3282; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22063282 - 23 Mar 2021

Cited by 8 | Viewed by 2025

Abstract

Sea buckthorn (Elaeagnus rhamnoides (L.) A. Nelson) is a shrub growing in coastal areas. Its organs contain a range of bioactive substances including vitamins, fatty acids, various micro and macro elements, as well as phenolic compounds. Numerous studies of sea buckthorn have found it to have anticancer, anti-ulcer, hepatoprotective, antibacterial, and antiviral properties. Some studies suggest that it also affects the hemostasis system. The aim of the study was to determine the effect of six polyphenols rich and triterpenic acids rich fractions (A–F), taken from various organs of sea buckthorn, on the activation of blood platelets using whole blood, and to assess the effect of the tested fractions on platelet proteins: fraction A (polyphenols rich fraction from fruits), fraction B (triterpenic acids rich fraction from fruits), fraction C (polyphenols rich fraction from leaves), fraction D (triterpenic acids rich fraction from leaves), fraction E (polyphenols rich fraction from twigs), and fraction F (triterpenic acids rich fraction from twigs). Hemostasis parameters were determined using flow cytometry and T-TAS (Total Thrombus-formation Analysis System). Additionally, electrophoresis was performed under reducing and non-reducing conditions. Although all tested fractions inhibit platelet activation, the greatest anti-platelet activity was demonstrated by fraction A, which was rich in flavonol glycosides. In addition, none of the tested fractions (A–F) caused any changes in the platelet proteome, and their anti-platelet potential is not dependent on the P2Y12 receptor. Full article

(This article belongs to the Special Issue Flavonoids)

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Review

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45 pages, 3796 KiB

Open AccessReview

Chirality Matters: Biological Activity of Optically Pure Silybin and Its Congeners

by Vladimír Křen

Int. J. Mol. Sci. 2021, 22(15), 7885; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22157885 - 23 Jul 2021

Cited by 18 | Viewed by 3596

Abstract

This review focuses on the specific biological effects of optically pure silymarin flavo-nolignans, mainly silybins A and B, isosilybins A and B, silychristins A and B, and their 2,3-dehydro derivatives. The chirality of these flavonolignans is also discussed in terms of their analysis, preparative separation and chemical reactions. We demonstrated the specific activities of the respective diastereomers of flavonolignans and also the enantiomers of their 2,3-dehydro derivatives in the 3D anisotropic systems typically represented by biological systems. In vivo, silymarin flavonolignans do not act as redox antioxidants, but they play a role as specific ligands of biological targets, according to the “lock-and-key” concept. Estrogenic, antidiabetic, anticancer, antiviral, and antiparasitic effects have been demonstrated in optically pure flavonolignans. Potential application of pure flavonolignans has also been shown in cardiovascular and neurological diseases. Inhibition of drug-metabolizing enzymes and modulation of multidrug resistance activity by these compounds are discussed in detail. The future of “silymarin applications” lies in the use of optically pure components that can be applied directly or used as valuable lead structures, and in the exploration of their true molecular effects. Full article

(This article belongs to the Special Issue Flavonoids)

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20 pages, 1552 KiB

Open AccessReview

A Comprehensive Review on Chemotaxonomic and Phytochemical Aspects of Homoisoflavonoids, as Rare Flavonoid Derivatives

by Javad Mottaghipisheh and Hermann Stuppner

Int. J. Mol. Sci. 2021, 22(5), 2735; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22052735 - 08 Mar 2021

Cited by 19 | Viewed by 3653

Abstract

Homoisoflavonoids (3-benzylidene-4-chromanones) are considered as an infrequent flavonoid class, possessing multi-beneficial bioactivities. The present study gives an overview on phytochemical aspects of homoisoflavonoids, including utilized plant species, parts, extracts, and separation techniques. Overall, these compounds have mainly been isolated and identified from bulbs and rhizomes of the plants belonging to Asparagaceae and Fabaceae families, particularly the genera of Ophiopogon, Dracaena, Scilla, Polygonatum, and Caesalpinia. Full article

(This article belongs to the Special Issue Flavonoids)

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