Antioxidant Sources from Leaves of Russian Dandelion

Antioxidants in Fruit Fractions of Mediterranean Ancient Pear Cultivars

BACKGROUND

The genetic diversity of Sardinian pear germplasm has received limited attention regarding its chemical composition. Understanding this composition can aid in the setting up of resilient, extensive groves that offer multiple products and ecosystem services. This research aimed at investigating the antioxidant properties and phenolic compounds of ancient pear cultivars grown extensively in Sardinia (Italy); Methods: the cultivars Buttiru, Camusina, Spadona, and Coscia (as a reference) were compared. Fruit samples were manually peeled and cut. Their flesh, peel, core, and peduncle were frozen separately, lyophilized, and milled before being analysed; Results: The content of total phenolics (TotP), total flavonoids (TotF), condensed tannins (CT), and antioxidant capacity in each fruit part varied significantly among the cultivars. The TotP content was high in the peduncle (42.2-58.8 g GAE kg^-1 DM) and low in flesh (6.4-17.7 g GAE kg^-1 DM); Conclusions: the highest values of antioxidant capacity, TotP, NTP, TotF, and CT were found in the flesh of the cultivar Buttiru and in the peel of the cultivar Camusina. Chlorogenic acid was the major individual phenolic compound in peel, flesh and core, whereas arbutin was mostly present in the peduncle. Results can contribute to revise target exploitations of underutilized ancient pear cultivars.

Molecular Genetic Research and Genetic Engineering of Taraxacum kok-saghyz L.E. Rodin

Natural rubber (NR) remains an indispensable raw material with unique properties that is used in the manufacture of a large number of products and the global demand for it is growing every year. The only industrially important source of NR is the tropical tree Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg., thus alternative sources of rubber are required. For the temperate zone, the most suitable source of high quality rubber is the Russian (Kazakh) dandelion Taraxacum kok-saghyz L.E. Rodin (TKS). An obstacle to the widespread industrial cultivation of TKS is its high heterozygosity, poor growth energy, and low competitiveness in the field, as well as inbreeding depression. Rapid cultivation of TKS requires the use of modern technologies of marker-assisted and genomic selection, as well as approaches of genetic engineering and genome editing. This review is devoted to describing the progress in the field of molecular genetics, genomics, and genetic engineering of TKS. Sequencing and annotation of the entire TKS genome made it possible to identify a large number of SNPs, which were subsequently used in genotyping. To date, a total of 90 functional genes have been identified that control the rubber synthesis pathway in TKS. The most important of these proteins are part of the rubber transferase complex and are encoded by eight genes for cis-prenyltransferases (TkCPT), two genes for cis-prenyltransferase-like proteins (TkCPTL), one gene for rubber elongation factor (TkREF), and nine genes for small rubber particle proteins (TkSRPP). In TKS, genes for enzymes of inulin metabolism have also been identified and genome-wide studies of other gene families are also underway. Comparative transcriptomic and proteomic studies of TKS lines with different accumulations of NR are also being carried out, which help to identify genes and proteins involved in the synthesis, regulation, and accumulation of this natural polymer. A number of authors already use the knowledge gained in the genetic engineering of TKS and the main goal of these works is the rapid transformation of the TKS into an economically viable rubber crop. There are no great successes in this area so far, therefore work on genetic transformation and genome editing of TKS should be continued, considering the recent results of genome-wide studies.

Subterranean Clover and Sulla as Valuable and Complementary Sources of Bioactive Compounds for Rainfed Mediterranean Farming Systems

Mediterranean pasture and forage legumes are important components of sustainable production systems. Subterranean clover and sulla represent key species having proven high agronomic value and traits for production and multiple services. Our research investigated the potential of the abovementioned species as a source of phenolic compounds and antioxidants for contributing to support their full exploitation in the fodder, animal welfare, and nutraceutical sectors. Antioxidant capacity, as well as the content of total phenolic compounds and individual phenolic compounds, was determined in subterranean clover and sulla shoots at the vegetative, flower bud, flowering, and seed ripening phenological stages. The antioxidant capacity and the phenolic content were affected significantly by harvest time. In subterranean clover, 10 individual phenolic compounds were detected, and isoflavones were the most abundant (3.19-18.27 mg·g^-1 DM). Eleven phenolic compounds were identified in sulla shoots, and chlorogenic acid (0.76-3.43 mg·g^-1 DM) and diosmin (3.64-4.94 mg·g^-1 DM) were the most represented compounds at the vegetative and flower bud stage. On the basis of our findings, a complementary utilization of both legume species is suggested; this might ensure the exploitation of all phenolic compounds in view of the potential benefits for animal production and health.

A jasmonate-responsive bHLH transcription factor TaMYC2 positively regulates triterpenes biosynthesis in Taraxacum antungense Kitag

Dandelion is a well-known traditional medical herb, also used as functional food. Dandelion possesses many medical properties, such as anti-bacterial and antioxidant activity and contains a variety of triterpenes, such as α-amyrin, β-amyrin, taraxerol and taraxasterol. In this study, we found that triterpenes biosynthesis was promoted by methyl jasmonate (MeJA), while the transcriptional mechanism underlying triterpenes biosynthesis was rarely investigated. Here, a MeJA-induced bHLH transcription factor TaMYC2 was identified. The content of taraxasterol and taraxerol in dandelion was obviously enhanced in overexpression TaMYC2 transgenic lines and expression level of the squalene synthase gene (TaSS) was elevated to about 3-5 folds compared with the control lines. Dual-LUC, Y1H and EMSA experiments revealed that TaMYC2 bound to the E-box motif in the promoter of TaSS and activated its transcription. Taken together, this study suggested that TaMYC2 acted as a positive regulator for bioengineering approaches to produce high content triterpenes-producing dandelions.

Comparative Analysis with GC–MS of Fatty Acids and Volatile Compounds of Taraxacum kok-saghyz Rodin and Taraxacum officinale as Edible Resource Plants

Taraxacum kok-saghyz Rodin (TKS) is a potential edible resource plant that is rich in inulin, lipid, protein and other active ingredients. In this study, HS-SPME/GC–MS was used to analyze volatile compounds (VCs) and profile the fatty acids in TKS roots and leaves, and the results were compared with those from Taraxacum officinale (TO). A total of 105 and 107 VCs were detected in the leaves and roots of seven dandelion samples (three TKS and four TO), amongst which the main VCs were ethyl tetradecanoate, ethyl linolenate, ethyl linoleate, dihydroactinidiolide, ethyl palmitate, β-ionone, 3,5-octadien-2-one, β-ionone 5,6-epoxide, geranyl acetone, benzaldehyde, safranal, 2-Pentylfuran, farnesene and β-elemene. Linoleic acid and linolenic acid were the dominant fatty acids in seven dandelion samples, and the ratio of unsaturated to saturated fatty acids was larger than 4. Principal component analysis showed that the differences in VCs and fatty acid levels between different dandelion samples mainly came from different places of origin, while the differences between different varieties in the same place of origin was minor; i.e., the VCs and fatty acid levels of TKS and TO collected from the same place were basically similar.

Identification of the WRKY Gene Family and Characterization of Stress-Responsive Genes in Taraxacum kok-saghyz Rodin

WRKY transcription factors present unusual research value because of their critical roles in plant physiological processes and stress responses. Taraxacum kok-saghyz Rodin (TKS) is a perennial herb of dandelion in the Asteraceae family. However, the research on TKS WRKY TFs is limited. In this study, 72 TKS WRKY TFs were identified and named. Further comparison of the core motifs and the structure of the WRKY motif was analyzed. These TFs were divided into three groups through phylogenetic analysis. Genes in the same group of TkWRKY usually exhibit a similar exon-intron structure and motif composition. In addition, virtually all the TKS WRKY genes contained several cis-elements related to stress response. Expression profiling of the TkWRKY genes was assessed using transcriptome data sets and Real-Time RT-PCR data in tissues during physiological development, under abiotic stress and hormonal treatments. For instance, the TkWRKY18, TkWRKY23, and TkWRKY38 genes were significantly upregulated during cold stress, whereas the TkWRKY21 gene was upregulated under heat-stress conditions. These results could provide a basis for further studies on the function of the TKS WRKY gene family and genetic amelioration of TKS germplasm.

The intestinal absorption mechanism of chicoric acid and its bioavailability improvement with chitosan

Chicoric acid (CA), an active phenolic acid of Echinacea purpurea (Linn.) Moench, has been demonstrated to exhibit antioxidative, antiviral and immunological activities. A prior study showed that CA is a water-soluble compound with low bioavailability. The current study was performed to study the intestinal absorption mechanism of CA and improve its bioavailability using natural biodegradable chitosan. A Caco-2 monolayer cell model was established to characterise the mechanisms involved in the intestinal absorption of CA. The bioavailability improvement of CA was studied in Sprague–Dawley rats after oral (20 mg/kg) administration of 0.5% chitosan. In vitro, the results showed that the absorption transport of CA was fairly poor, with Papp values of 8.2 × 10⁻⁸ to 2.1 × 10⁻⁷ cm/s in the absorption direction and 1.5 × 10⁻⁷ to 2.6 × 10⁻⁷ cm/s in the secretory direction. The permeability was increased by EDTA and chitosan in both directions. Moreover, the transport through the intestinal monolayer was H⁺ dependent, and P-glycoprotein and OATP2B1 transporters were involved in the intestinal transport of CA. In vivo, the absorption of CA was increased and accelerated with chitosan in rats because the bioavailability was 1.74-fold that of the prototype drug. The above mentioned results indicated that CA was a poor absorption drug and that paracellular and carrier-mediated trancellular transport both participated in its transport route. Chitosan is an excellent absorption enhancer for CA. The transport characteristics uncovered in this study lay the groundwork for further studies directed toward the development and utilisation of its new formulations.

In vivo assessment of antioxidant, antigenotoxic, and antimutagenic effects of bark ethanolic extract from Spondias purpurea L

Medicinal plants have always been used for therapeutic purposes; however, some plants may contain toxic and mutagenic substances. The aim of this study was to assess the cytotoxic, genotoxic, mutagenic, antioxidant, antigenotoxic, and antimutagenic effects of the bark ethanolic extract of Spondias purpurea L. using male and female Swiss albino mice. To determine the protective effects of the extract, benzo[a]pyrene (B[a]P) and cyclophosphamide (CP) were selected as cell damage inducers. The extract was examined at doses of 500, 1000, or 1500 mg/kg body weight (BW)via gavage alone or concomitant with B[a]P or CP. Oxidative stress was measured by quantification of blood catalase activity (CAT), reduced glutathione (GSH) levels in total blood, liver, and kidney, and concentrations of malondiadehyde (MDA) in liver and kidney. Genotoxicity and antigenotoxicity were evaluated by the comet assay using peripheral blood. Cytotoxicity, mutagenicity, and antimutagenicity were determined utilizing the micronucleus test in bone marrow and peripheral blood. The S. purpurea L extract increased CAT activity and GSH levels accompanied by a decrease in MDA levels after treatment with B[a]P and CP. No genotoxic, cytotoxic, or mutagenic effects were found in mice exposed only to the extract. These results indicate that the extract of S. purpurea exhibited protective effects against oxidative and DNA damage induced by B[a]P and CP.

Antioxidant Contents in a Mediterranean Population of Plantago lanceolata L. Exploited for Quarry Reclamation Interventions

Plantago lanceolata L. (plantain) is an interesting multipurpose perennial species whose aerial parts are used in herbal medicine due to its precious phytochemicals and are palatable to animals. Moreover, peculiar traits such as drought tolerance, an extended growth season and a deep root system, make plantain a promising pioneer plant for quarry reclamation based on the use of native species. This study evaluated the effects of different environmental conditions and seasons on the accumulation of the bioactive compounds of its aerial organs. An autochthonous plantain population was grown in three locations in Sardinia (Italy). Leaves, peduncles and inflorescences were collected between October 2020 and July 2021. Phenolic contents and antioxidant capacity were determined. The analysis of the individual phenolic compounds was performed using liquid chromatography. In leaves, the content of total phenolics, antioxidant capacity and total flavonoids were significantly influenced by location and season. Total phenolic content ranged from 65 to 240 g gallic acid equivalent kg^-1, whereas total flavonoids were from 16 to about 89 g catechin equivalent kg^-1. Neochlorogenic, chlorogenic, cryptochlorogenic acids, verbascoside, diosmin and luteolin were identified in the methanolic extracts of leaves, peduncles and inflorescences. Verbascoside was the main antioxidant isolated from plantain extracts. Results evidenced an increasing accumulation pattern of phenolics from vegetative stage to flowering, followed by a decrement towards the seed ripening as well as site-specific differences with amounts of phenolics even 25% higher for same plantain accession.

CRISPR/Cas genome editing to optimize pharmacologically active plant natural products

Since time immemorial, human use medicinal plants as sources of food, therapy and industrial purpose. Classical biotechnology and recent next-generation sequencing (NGS) techniques have been successfully used to optimize plant-derived natural-products of biomedical significance. Earlier, protein based editing tools viz. zinc-finger nucleases (ZFNs) and transcription activator-like endonucleases (TALENs) have been popularized for transcriptional level genome manipulation. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated9 (Cas9) endonuclease system is an efficient, robust and selective site-directed mutagenesis strategy for RNA-guided genome-editing. CRISPR/Cas9 genome-editing tool employs designed guide-RNAs that identifies a 3 base-pair protospacer adjacent motif (PAM) sequence occurring downstream of the target-DNA. The present review comprehensively complies the recent literature (2010-2020) retrieved from scientific-databases on the application of CRISPR/Cas9-editing-tools as potent genome-editing strategies in medicinal-plants discussing the recent developments, challenges and future-perspectives with notes on broader applicability of the technique in plants and lower-organisms. In plants, CRISPR/Cas-editing has been implemented successfully in relation to crop-yield and stress-tolerance. However, very few medicinal plants have been edited using CRISPR/Cas genome tool owing to the lack of whole-genome and mRNA-sequences and shortfall of suitable transformation and regeneration strategies. However, recently a number of plant secondary metabolic-pathways (viz. alkaloid, terpenoid, flavonoids, phenolic, saponin etc.) have been engineered employing CRISPR/Cas-editing via knock-out, knock-in, point-mutation, fine-tuning of gene-expression and targeted-mutagenesis. This genome-editing tool further extends its applicability incorporating the tools of synthetic- and systems-biology, functional-genomics and NGS to produce genetically-engineered medicinal-crops with advanced-traits facilitating the production of pharmaceuticals and nutraceuticals.

Comparison of Bioactive Phenolic Compounds and Antioxidant Activities of Different Parts of Taraxacum mongolicum

Herbs derived from Taraxacum genus have been used as traditional medicines and food supplements in China for hundreds of years. Taraxacum mongolicum is a famous traditional Chinese medicine derived from Taraxacum genus for the treatment of inflammatory disorders and viral infectious diseases. In the present study, the bioactive phenolic chemical profiles and antioxidant activities of flowers, leaves, and roots of Taraxacum mongolicum were investigated. Firstly, a high performance liquid chromatography method combined with segmental monitoring strategy was employed to simultaneously determine six bioactive phenolic compounds in Taraxacum mongolicum samples. Moreover, multivariate statistical analysis, including hierarchical clustering analysis, principal component analysis, and partial least squares discriminant analysis were performed to compare and discriminate different parts of Taraxacum mongolicum based on the quantitative data. The results showed that three phenolic compounds, caftaric acid, caffeic acid, and luteolin, could be regarded as chemical markers for the differences of flowers, leaves, and roots of Taraxacum mongolicum. In parallel, total phenolic contents, total flavonoid contents and antioxidant activities of different parts of Taraxacum mongolicum were also evaluated and compared. It is clear that Taraxacum mongolicum had antioxidant properties, and the antioxidant capacities of different parts of Taraxacum mongolicum in three antioxidant assays showed a similar tendency: Flowers ≈ leaves > roots, which revealed a positive relationship with their total phenolic and flavonoid contents. Furthermore, to find the potential antioxidant components of Taraxacum mongolicum, the latent relationships of the six bioactive phenolic compounds and antioxidant activities of Taraxacum mongolicum were investigated by Pearson correlation analysis. The results indicated caftaric acid and caffeic acid could be the potential antioxidant ingredients of Taraxacum mongolicum. The present work may facilitate better understanding of differences of bioactive phenolic constituents and antioxidant activities of different parts of Taraxacum mongolicum and provide useful information for utilization of this herbal medicine.

Bioactive Compounds from Leaves and Twigs of Guayule Grown in a Mediterranean Environment

Guayule (Parthenium argentatum) is one of the most promising alternatives to produce natural rubber. As the guayule leaves represent a waste byproduct in the rubber extraction process, their exploitation might contribute to the valorization of the whole plant biomass. The specific aim of our study was to determine the antioxidant capacity and the content of phenolic compounds in leaves and twigs of different guayule lines cultivated in a Mediterranean environment. The antioxidant capacity and the contents of phenolic were affected significantly by guayule accession and harvest time. Overall means in twigs represented about 60% of the corresponding leaf values for antioxidant capacity as DPPH (1,1-diphenyl-2-picrylhydrazyl) and not tannic phenolic and about 55% as ABTS (2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt), total phenolic, tannic phenolic and total flavonoid contents. Five individual phenolic compounds were identified in methanolic extracts of leaves. Neochlorogenic acid (62.5–174.8 mg g⁻¹ DW) and chlorogenic acid (28.6–41.1 mg g⁻¹ DW) were the most abundant phenolic acids. In addition to the compounds quantified in leaves, cynarin was identified only in twigs and for the first time in guayule biomass. Our results indicate that guayule leaves and twigs represent a rich source of antioxidants for potential applications in fodder, nutraceutical and pharmacological sectors.