Primary and Secondary Metabolites in Fruits and Vegetables; Analytical Solutions, Chemical Composition and Bioavailability Evaluation

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Phytochemistry".

Deadline for manuscript submissions: 31 December 2024 | Viewed by 4967

Special Issue Editor


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Guest Editor
Department of Agronomy, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia
Interests: primary and secondary metabolites; biological potential of grapevine and fruit species; resistance mechanisms; plant–environment interaction; food chemistry; wine, high-performance liquid chromatography; mass spectrometry; natural product chemistry; antioxidants, bioactive compounds, food processing techniques, analytical methods, secondary metabolism, plant extracts, phytochemicals, fruit quality, plant extracts with biological activity, development of innovative products
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Special Issue Information

Dear Colleagues,

In plants, basic functions are largely performed by primary metabolites. Primary metabolites are substances that are absolutely necessary for plant growth and development and play an important role in plant metabolism. Primary metabolites include sugars, organic acids and amino acids. Primary metabolites play an important role in maintaining the quality and determining the nutritional value of fruits. Sugars and organic acids also influence the taste and flavour of fruits and vegetables.

In addition to primary metabolites, plants also have substances called secondary metabolites that are formed from primary metabolites. According to their biosynthetic origin, they are divided into three main groups: terpenoids or terpenes, nitrogenous compounds and phenolic compounds. Nitrogenous compounds include compounds such as alkaloids, glucosinolates and cyanogenic glycosides. Nitrogenous compounds are synthesized from amino acids and contain nitrogen (N). The plant accumulates them in different parts of its composition and in different concentrations. They have a defensive function, protecting the plant from natural enemies and pathogens, and can be toxic to some insects and mammals. Terpenoids are composed of isoprene units, and are substances that are mainly involved in protecting the plant from stressful environmental factors; they are in communication between plants and other organisms. Phenolic compounds consist of an aromatic ring and hydroxyl groups and are the most abundant secondary metabolites in fruits and vegetables. Most phenolic compounds are esters or glycosides. Phenolic compounds provide protection to plants from stressors, are involved in flower and fruit pigmentation and also contribute to fruit flavour and aroma. Some phenolic compounds have allelopathic effects, meaning that they can inhibit or stimulate the growth of neighbouring plants. In addition, individual secondary compounds can also be growth regulators and germination inhibitors, or can simply provide a nitrogen reserve.

The content of primary and secondary compounds in fruits and vegetables is influenced by various factors such as variety, genotype, growing conditions, ripening stages, agricultural practices, postharvest storage conditions and processing methods. Many environmental factors, such as the availability and accessibility of nutrients and water, light and temperature, can influence the synthesis and accumulation of secondary metabolites. In addition to abiotic factors, there are also plant-damaging organisms in nature, such as herbivores, nematodes, fungi and bacteria, against which the plant also protects itself by synthesising certain secondary components.

Some compounds from secondary metabolites also have bioactive activity. This means that they cause reactions or trigger a response in living tissues. Compounds are biologically active if they have a direct effect on the organism, either positive or negative. Secondary metabolites are also useful to humans as they are commonly used as medicines, flavourings, spices and dietary supplements. The content of secondary metabolites depends primarily on the plant species and on their function in the life cycle of the plant. For humans, information about their content in fruits is extremely important, especially from the point of view of their beneficial or harmful effect when absorbed into the body. The beneficial effects of fruits and vegetables depend mainly on the concentration of phenolic acids, flavonoids, carotenoids, anthocyanins, vitamins and minerals. Clinical studies have shown that the consumption of fruits and vegetables high in anthocyanins and other phenolic substances can reduce the risk of obesity, cardiovascular diseases, degenerative diseases and various cancers. The reason for this lies in their antioxidant effect.

This Special Issue of Plants will focus on the diversity in the occurrence of primary and secondary metabolites in different fruits and vegetables, their content and function in plants and analytical methods for their precise extraction and analysis. At the same time, we are also interested in how the different environmental conditions of the site (drought, stress, nutrients, soil pH, etc.), different cultivation techniques (fertilisation, spraying, irrigation, etc.) and fruit processing technologies (pasteurisation, pressing, different substances, etc.) affect the preservation of their bioactive value. With the help of new results from the field of metabolites in fruits and vegetables, their usefulness in the field of phytochemistry, pharmacy, public health, the food industry and agriculture will be much greater. In addition, the improved effects of the extraction of metabolites from plant tissues and the preservation of their content in food require special attention so that in the technological processes of fruit and vegetable processing, their functional properties are not affected and the consumer receives a good-quality product.

Dr. Maja Mikulič-Petkovšek
Guest Editor

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Keywords

  • phytochemistry
  • primary and secondary metabolites
  • fruits and vegetables
  • analytical techniques
  • environmental factors
  • production technology
  • horticultural crops
  • sugars
  • organic acids
  • polyphenolics
  • cyanogenic glycosides
  • glucosinolates
  • terpenoids
  • extraction
  • drying
  • natural product chemistry
  • novel processing technologies
  • flavonoids
  • phenolic-rich extracts
  • herbal medicine
  • disease management
  • development of innovative products
  • fruit quality
  • bioactive compounds
  • final product
  • stability of substances
  • antioxidant properties
  • health status
  • resistant cultivars
  • plant growth responses
  • phenylpropanoid pathway
  • enzymes
  • biotic and abiotic stress
  • storage
  • postharvest technology
  • nutrients
  • sustainable approach
  • plant biostimulators
  • oxidative stress
  • adaptive mechanisms
  • plant diseases
  • elicitors

Published Papers (4 papers)

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Research

17 pages, 5147 KiB  
Article
Use of Secondary Metabolites Profiling and Antioxidant Activity to Unravel the Differences between Two Species of Nettle
by Julia Baumli, Norbert Antal, Dorina Casoni and Claudia Cimpoiu
Plants 2023, 12(18), 3233; https://doi.org/10.3390/plants12183233 - 11 Sep 2023
Viewed by 1091
Abstract
In recent years, the interest in natural remedies has increased, so it is important to analyze the plants widely distributed in nature but whose composition is little known. The main objective of the present work is to obtain information based on the profiles [...] Read more.
In recent years, the interest in natural remedies has increased, so it is important to analyze the plants widely distributed in nature but whose composition is little known. The main objective of the present work is to obtain information based on the profiles of secondary metabolites and antioxidant activity in Lamium album, a very widespread but little studied plant, with the aim of revealing the differences compared to Urtica dioica. First, the optimization of enzymatic extraction assisted by ultrasound was carried out by the Box–Behnken method. The optimized parameters were: concentration of the enzyme—3.3% cellulase, temperature—55 °C, and the extraction time—40.00 min. The efficiency was estimated based on the content of iridoids, the main class of secondary metabolites from Lamium album. Second, the secondary metabolites profiles of the nettle extracts were obtained by thin-layer chromatography using both normal and reverse phases and by RP-UHPLC. The antioxidant activity was evaluated using DPPH and ABTS+ radicals. The obtained results revealed significant differences between the two nettle species, both in terms of the phytochemical compounds, as well as the antioxidant activity, confirming the fact that Lamium album has a high potential to be used in phytomedicine. Full article
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20 pages, 2413 KiB  
Article
Assessing the RP-LC-MS-Based Metabolic Profile of Hass Avocados Marketed in Europe from Different Geographical Origins (Peru, Chile, and Spain) over the Whole Season
by Irene Serrano-García, Joel Domínguez-García, Elena Hurtado-Fernández, José Jorge González-Fernández, José Ignacio Hormaza, María Gemma Beiro-Valenzuela, Romina Monasterio, Romina Pedreschi, Lucía Olmo-García and Alegría Carrasco-Pancorbo
Plants 2023, 12(16), 3004; https://doi.org/10.3390/plants12163004 - 20 Aug 2023
Cited by 2 | Viewed by 1335
Abstract
Spain dominates avocado production in Europe, with the Hass variety being the most prominent. Despite this, Spanish production satisfies less than 10% of the overall avocado demand in Europe. Consequently, the European avocado market heavily relies on imports from overseas, primarily sourced from [...] Read more.
Spain dominates avocado production in Europe, with the Hass variety being the most prominent. Despite this, Spanish production satisfies less than 10% of the overall avocado demand in Europe. Consequently, the European avocado market heavily relies on imports from overseas, primarily sourced from Peru and Chile. Herein, a comprehensive characterization of the metabolic profile of Hass avocado fruits from Spain, Peru, and Chile, available in the European market throughout the year, was carried out. The determination of relevant substances was performed using high- and low-resolution RP-LC-MS. Remarkable quantitative differences regarding phenolic compounds, amino acids, and nucleosides were observed. Principal component analysis revealed a natural clustering of avocados according to geographical origin. Moreover, a specific metabolic pattern was established for each avocado-producing country using supervised partial least squares discriminant analysis. Spanish fruits exhibited high levels of coumaric acid malonyl-hexose II, coumaric acid hexose II, and ferulic acid hexose II, together with considerably low levels of pantothenic acid and uridine. Chilean avocado fruits presented high concentrations of abscisic acid, uridine, ferulic acid, succinic acid, and tryptophan. Fruits from Peru showed high concentrations of dihydroxybenzoic acid hexose, alongside very low levels of p-coumaric acid, ferulic acid, coumaric acid malonyl-hexose I, and ferulic acid hexose II. Full article
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17 pages, 2501 KiB  
Article
Evaluation of the Antifungal Potential of Grape Cane and Flesh-Coloured Potato Extracts against Rhizoctonia sp. in Solanum tuberosum Crops
by Francisca Gómez, Catalina Bravo, Isidora Ringler, Christian Santander, Felipe González, Franco Viscarra, Claudia Mardones, Boris Contreras, Pablo Cornejo and Antonieta Ruiz
Plants 2023, 12(16), 2974; https://doi.org/10.3390/plants12162974 - 17 Aug 2023
Viewed by 818
Abstract
Potato (Solanum tuberosum) is one of the most important food crops worldwide, and Rhizoctonia solani infection is one of the most common diseases. The objective of this study was to evaluate the antifungal activity of Vitis vinifera byproducts (VIDES) and flesh-coloured [...] Read more.
Potato (Solanum tuberosum) is one of the most important food crops worldwide, and Rhizoctonia solani infection is one of the most common diseases. The objective of this study was to evaluate the antifungal activity of Vitis vinifera byproducts (VIDES) and flesh-coloured potato (FCP) extracts against Rhizoctonia sp. in potato crops. Photosynthetic traits, phenolic profiles, and antioxidant and enzymatic activities were determined. The VIDES extract showed a 151.4% improvement in stomatal conductance and a 258.5% improvement in the photosynthetic rate compared to the plants without infection. Regarding the enzymatic antioxidant activity, the best response was found in the FCP treatments with 30 min of application, with increases of 25%, 161%, and 450% in ascorbate peroxidase, catalase (CAT), and glutathione reductase (GR) activities, respectively, compared to plants without infection. For the VIDES extract, a 15 min application produced an 83% increase in CAT activity, whereas a 181% increase in GR activity compared to plants without infection was produced after a 30 min application. A similar behaviour was observed for antioxidant compounds, where FCP had a higher concentration of compounds and antioxidant activity. This finding suggests that FCP and VIDES promote the synthesis of plant-defence compounds against Rhizoctonia sp. in potato crops, in which the application time is a determining factor. Full article
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23 pages, 6802 KiB  
Article
Biochemical and Phylogenetic Analysis of Italian Phaseolus vulgaris Cultivars as Sources of α-Amylase and α-Glucosidase Inhibitors
by Stefania Peddio, Sonia Lorrai, Alessandra Padiglia, Faustina B. Cannea, Tinuccia Dettori, Viviana Cristiglio, Luigi Genovese, Paolo Zucca and Antonio Rescigno
Plants 2023, 12(16), 2918; https://doi.org/10.3390/plants12162918 - 11 Aug 2023
Viewed by 927
Abstract
Phaseolus vulgaris α-amylase inhibitor (α-AI) is a protein that has recently gained commercial interest, as it inhibits mammalian α-amylase activity, reducing the absorption of dietary carbohydrates. Numerous studies have reported the efficacy of preparations based on this protein on the control of glycaemic [...] Read more.
Phaseolus vulgaris α-amylase inhibitor (α-AI) is a protein that has recently gained commercial interest, as it inhibits mammalian α-amylase activity, reducing the absorption of dietary carbohydrates. Numerous studies have reported the efficacy of preparations based on this protein on the control of glycaemic peaks in type-2 diabetes patients and in overweight subjects. A positive influence on microbiota regulation has also been described. In this work, ten insufficiently studied Italian P. vulgaris cultivars were screened for α-amylase- and α-glucosidase-inhibiting activity, as well as for the absence of antinutritional compounds, such as phytohemagglutinin (PHA). All the cultivars presented α-glucosidase-inhibitor activity, while α-AI was missing in two of them. Only the Nieddone cultivar (ACC177) had no haemagglutination activity. In addition, the partial nucleotide sequence of the α-AI gene was identified with the degenerate hybrid oligonucleotide primer (CODEHOP) strategy to identify genetic variability, possibly linked to functional α-AI differences, expression of the α-AI gene, and phylogenetic relationships. Molecular studies showed that α-AI was expressed in all the cultivars, and a close similarity between the Pisu Grogu and Fasolu cultivars’ α-AI and α-AI-4 isoform emerged from the comparison of the partially reconstructed primary structures. Moreover, mechanistic models revealed the interaction network that connects α-AI with the α-amylase enzyme characterized by two interaction hotspots (Asp38 and Tyr186), providing some insights for the analysis of the α-AI primary structure from the different cultivars, particularly regarding the structure–activity relationship. This study can broaden the knowledge about this class of proteins, fuelling the valorisation of Italian agronomic biodiversity through the development of commercial preparations from legume cultivars. Full article
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