Glucosinolate variation in leaves of Brassica rapa crops

Chemical Profile of Turnip According to the Plant Part and the Cultivar: A Multivariate Approach

Turnip (Brassica rapa subsp. rapa) is a cruciferous plant cultivated worldwide that serves as a source of nutrients and bioactive compounds. Most turnip studies have focused on a few compounds or on part of the plant. The establishment of a complete chemical profile of different plant parts would facilitate its use for nutritional and medicinal purposes. In the current study, mineral elements, soluble sugars, free amino acids (FAA), total phenols (TP), total flavonoids (TF), and glucosinolates (GS) were quantified in the leaves, stems, and roots. Results were compared for 20 strains of turnip. The outcomes showed significant differences between parts of the plant and strains. The leaves exhibited the highest TF, TP, indispensable FAA, and microelement levels, and they showed a higher GS. Moreover, the stems had a high content of GS and macroelements. Furthermore, the roots showed high levels of free sugars and total FAA. The findings of this work provide the basis for utilizing each part of the turnip plant based on its chemical composition.

New vegetable varieties of Brassica rapa and Brassica napus with modified glucosinolate content obtained by mass selection approach

Background

Glucosinolates (GSLs) constitute a characteristic group of secondary metabolites present in the Brassica genus. These compounds confer resistance to pests and diseases. Moreover, they show allelopathic and anticarcinogenic effects. All those effects are dependent on the chemical structure of the GSL. The modification of the content of specific GSLs would allow obtaining varieties with enhanced resistance and/or improved health benefits. Moreover, the attainment of varieties with the same genetic background but with divergent GSLs concentration will prompt the undertaking of studies on their biological effects.

Objective and Methods

The objective of this study was to evaluate the efficacy of two divergent mass selection programs to modify GSL content in the leaves of two Brassica species: nabicol (Brassica napus L.), selected by glucobrassicanapin (GBN), and nabiza (Brassica rapa L.), selected by gluconapin (GNA) through several selection cycles using cromatographic analysis.

Results

The response to selection fitted a linear regression model with no signs of variability depletion for GSL modification in either direction, but with higher efficiency in reducing the selected GSL than in the increasing. The selection was also effective in other parts of the plant, suggesting that there is a GSL translocation in the plant or a modification in their synthesis pathway that is not-organ specific. There was an indirect response of selection in other GSL; thus this information should be considered when designing breeding programs. Finally, populations obtained by selection have the same agronomic performance or even better than the original population.

Conclusion

Therefore, mass selection seems to be a good method to modify the content of specific GSL in Brassica crops.

Bioaccessibility of glucosinolates, isothiocyanates and inorganic micronutrients in cruciferous vegetables through INFOGEST static in vitro digestion model

Green tissues and seeds from cruciferous vegetables growing in conventional and ecological conditions (Brassica carinata; Brassica rapa; Eruca vesicaria and Sinapis alba) were analyzed to determine their contents of glucosinolates, isotihiocyanates (ITCs) and inorganic micronutrients (Ca, Cr, Cu, Fe, Mn, Ni, Se and Zn), and the bioaccessibility of these compounds. Regarding total contents and bioaccessibility values of these compounds, no clear difference was found between the organic and conventional systems. Glucosinolates bioaccessibility present in green tissues were high, with values around 60-78%. In additon, it was quantified in bioaccessible fraction ITCs concentrations such as Allyl - ITC; 3 - Buten - 1 - yl - ITC and 4 - Penten - 1 - yl - ITC. Trace elements bioaccessibility in green tissues was also high for Ca (2.26-7.66 mg/g), Cu (0.60-2.78 µg/g), Se (9.93-74.71 µg/Kg) and Zn (12.98-20.15 µg/g). By contrast, the bioaccessibility of glucosinolates and trace elements in cruciferous seeds was extremely low. With the exception of Cu, these bioaccessibility percentages did not exceed 1% in most cases.

Genome-Wide Association Study of Glucosinolate Metabolites (mGWAS) in Brassica napus L

Glucosinolates (GSLs) are secondary plant metabolites that are enriched in rapeseed and related Brassica species, and they play important roles in defense due to their anti-nutritive and toxic properties. Here, we conducted a genome-wide association study of six glucosinolate metabolites (mGWAS) in rapeseed, including three aliphatic glucosinolates (m145 gluconapin, m150 glucobrassicanapin and m151 progoitrin), one aromatic glucosinolate (m157 gluconasturtiin) and two indole glucosinolates (m165 indolylmethyl glucosinolate and m172 4-hydroxyglucobrassicin), respectively. We identified 113 candidate intervals significantly associated with these six glucosinolate metabolites. In the genomic regions linked to the mGWAS peaks, 187 candidate genes involved in glucosinolate biosynthesis (e.g., BnaMAM1, BnaGGP1, BnaSUR1 and BnaMYB51) and novel genes (e.g., BnaMYB44, BnaERF025, BnaE2FC, BnaNAC102 and BnaDREB1D) were predicted based on the mGWAS, combined with analysis of differentially expressed genes. Our results provide insight into the genetic basis of glucosinolate biosynthesis in rapeseed and should facilitate marker-based breeding for improved seed quality in Brassica species.

Alien Plants are Less Palatable to Pest Herbivores than Native Plants: Evidence from Cafeteria Experiments in Search of Suitable Plant Species to Restore Degraded Ecosystems

Nowadays, the ecology and evolutionary potential of alien species are the subjects of several ecological studies. The goal of this study was to compare the feeding preference of Arion ater on seedlings and leaves of alien and native plant species. Seedlings of three native species and one alien species were offered to slugs individually and in combination. Afterward, leaf discs from the native and alien species collected from the same source site of slug’s habitat were offered individually and in combination for slugs. When the new plant emerges, it constitutes a generous source of potential food and slugs would even feed on seedlings, which are not particularly palatable. Nonetheless, when given a choice, slug often preferentially feeds on some food items while ignoring others. Alien plants are more resistant to herbivory than native plants. There is a general tendency for alien species to be less palatable than native species. In general, slugs may eat a wide range of seedlings that are much more attractive than mature plants of the same species. Therefore, the native herbivores were found to attack native plants and promoted alien plants. Consequently, highly unacceptable alien species such as Eucalyptus globulus may play an important role in the restoration process.

Phytochemical characterization of turnip greens (Brassica rapa ssp. rapa): A systematic review

Objective

The Turnip (Brassica rapa L. ssp. rapa) is a leaf and root vegetable grown and consumed worldwide. The consumption of Turnip has been associated with beneficial effects on human health due to their phytochemicals that may control a variety of physiological functions, including antioxidant activity, enzyme regulation, and apoptotic control and the cell cycle. The current systematic review of the literature aims to evaluate both the profile and quantity of phytochemicals commonly found in Turnip greens and to provide perspectives for further investigation.

Methods

This review was conducted following the PRISMA guidelines. Four bibliographic databases (PubMed, Embase, Web-of-Science and Cochrane Central Register of Controlled Trials) were searched to identify published studies until April 8th, 2020 (date last searched) without data and language restriction. Studies were included if they used samples of Turnip greens (the leaves), and evaluated its phytochemical content. Two reviewers independently evaluated the titles and abstracts according to the selection criteria. For each potentially eligible study, two reviewers assessed the full-texts and independently extracted the data using a predesigned data extraction form.

Results

Based on the search strategy 5,077 potentially relevant citations were identified and full texts of 37 studies were evaluated, among which 18 studies were eligible to be included in the current review. The majority of included studies were focused on identification of glucosinolates and isothiocyanates (n = 14, 82%), four studies focused on organic acids, and five studies reported phenolic component profile in Turnip greens. Among included studies nine studies (50%) provided information on phytochemical’s content. We found 129 phytochemicals (19 glucosinolates, 33 glucosinolate-breakdown products, 10 organic acids and 59 polyphenolic compounds) reported in Turnip greens. Flavonoids were mainly present as quercetin, kaempferol and isorhamnetin derivatives; while aliphatic forms were the predominant glucosinolate (gluconapin was the most common across five studies, followed by glucobrassicanapin). In general, the phytochemical content varied among the leaves, tops and Turnip roots.

Conclusions

Emerging evidence suggests the Turnip as a substantial source of diverse bioactive compounds. However, detailed investigation on the pure compounds derived from Turnip green, their bioavailability, transport and metabolism after consumption is further needed. Additional studies on their biological activity are crucial to develop dietary recommendations on the effective dosage and dietary recommendation of Turnip greens for nutrition and health.

Glucosinolates and Isothiocyanates from Moringa oleifera: Chemical and Biological Approaches

Alternative therapies, such as phytotherapy, are considered to improve the health status of people with chronic non-communicable diseases (CNCDs). In this regard, Moringa oleifera is currently being studied for its nutritional value and its total phenolic content. Besides phenolic compounds, the phytochemical composition is also of great interest. This composition is characterized by the presence of glucosinolates and isothiocyanates. Isothiocyanates formed by the biotransformation of Moringa glucosinolates contain an additional sugar in their chemical structure, which provides stability to these bioactive compounds over other isothiocyanates found in other crops. Both glucosinolates and isothiocyanates have been described as beneficial for the prevention and improvement of some chronic diseases. The content of glucosinolates in Moringa tissues can be enhanced by certain harvesting methods which in turn alters their final yield after extraction. This review aims to highlight certain features of glucosinolates and isothiocyanates from M. oleifera, such as their chemical structure, functionality, and main extraction and harvesting methods. Some of their health-promoting effects will also be addressed.

Quantification and in vitro bioaccessibility of glucosinolates and trace elements in Brassicaceae leafy vegetables

Leaf samples from five Brassicaceae species (Brassica carinata, Brassica oleracea, Brassica rapa, Eruca vesicaria and Sinapis alba) were analyzed to determine their contents of glucosinolates and trace elements, and the bioaccessibility of these compounds. Considerable variability in the total contents and glucosinolate profiles was observed in the Brassicaceae species, with the total amounts ranging from 8.5 µmol/g dw in Brassica oleracea to 32.9 µmol/g dw in Sinapis alba. Bioaccessibilities of the predominant glucosinolates were moderate, ranging from 13.1% for glucoraphanin to 43.2% for gluconapin, which is particularly relevant as they have been implicated in a variety of anti-carcinogenic mechanisms. Trace element concentrations were: Se (28-160 µg/Kg dw); Cr (0.31-4.03 µg/g dw); Ni (0.19-1.53 µg/g dw); Fe (8.6-18.8 µg/g dw); Zn (20.8-41.5 µg/g dw); Ca (6.2-15.2 mg/g dw). Brassicaceae leaves were also moderate dietary sources of Se, Ni, Zn and Ca.

Nutritional Characterization of Two Rare Landraces of Turnip (Brassica rapa. var. rapa) Tops and Their On-Farm Conservation in Foggia Province

The study of nutritional properties in landrace products and the general context of its cultivation site are crucial to designing a sustainable on-farm strategy for landrace conservation. The present study describes the main nutritional aspects of two Brassica rapa subspecies rapa landraces collected in Puglia, Italy along with agroecological and socioeconomical traits where they are cultivated. The two B. rapa landraces (‘Cima di rapa dalla testa’ and ‘Cima di rapa antica’) are only found in sites at 700–800 m asl and in two landscape units (the Southern Daunian Mountains (SDM) and the Umbra Forest (UF), respectively) of the Foggia province. These rare landraces were selected by farmers to produce turnip greens/tops from ancient root turnip crops. They are named and consumed by local people in the same way as turnip tops of Brassica rapa subspecies sylvestris (‘Cima di rapa’), which are widely cultivated in Puglia. Compared to the most common ‘Cima di rapa’, the two highlighted landraces have a better nutritional profile linked to an improved content in antioxidant compounds—i.e., vitamin C (458 mg kg−1 FW), total phenols (347 mg ac. gallic equivalent kg−1 FW)—in glucosinolate (741 µmol kg FW−1, in ‘Cima di rapa antica’) and in minerals, such as K. Both landraces are deemed as having a high risk of erosion. Few exemplars are cultivated in marginal lands and urban/peri-urban areas (SDM), or in isolated sites within the UF, which is a special protection zone within Gargano National Park. However, natural, cultural, and recreational tourism are the main economic activities in both landscape units.

Exploring glucosinolates diversity in Brassicaceae: a genomic and chemical assessment for deciphering abiotic stress tolerance

Brassica is one of the most economically important genus of the Brassicaceae family, encompassing several key crops like Brassica napus (cabbage) and broccoli (Brassica oleraceae var. italica). This family is well known for their high content of characteristic secondary metabolites such as glucosinolates (GLS) compounds, recognize for their beneficial health properties and role in plants defense. In this work, we have looked through gene clusters involved in the biosynthesis of GLS, by combining genomic analysis with biochemical pathways and chemical diversity assessment. A total of 101 Brassicaceae genes involved in GLS biosynthesis were identified, using a multi-database approach. Through a UPGMA and PCA analysis on the 101 GLS genes recorded, revealed a separation between the genes mainly involved in GLS core structure synthesis and genes belonging to the CYP450s and MYBs gene families. After, a detailed phylogenetic analysis was conducted to better understand the disjunction of the aliphatic and indolic genes, by focusing on CYP79F1-F2 and CYP81F1-F4, respectively. Our results point to a recent diversification of the aliphatic CYP79F1 and F2 genes in Brassica crops, while for indolic genes an earliest diversification is observed for CYP81F1-F4 genes. Chemical diversity revealed that Brassica crops have distinct GLS chemo-profiles from other Brassicaceae genera; being highlighted the high contents of GLS found among the Diplotaxis species. Also, we have explored GLS-rich species as a new source of taxa with great agronomic potential, particularly in abiotic stress tolerance, namely Diplotaxis, the closest wild relatives of Brassica crops.

Expression profiles of BrMYB transcription factors related to glucosinolate biosynthesis and stress response in eight subspecies of Brassica rapa

Brassica rapa is a polyploid species with phenotypically diverse cultivated subspecies. Glucosinolates (GSLs) are secondary metabolites that contribute to anticarcinogenic activity and plant defense in Brassicaceae. Previously, complete coding sequences of 13 BrMYB transcription factors (TFs) related to GSL biosynthesis were identified in the B. rapa genome. In the present study, we investigated GSL content and expression levels of these BrMYBTFs in 38 accessions belonging to eight subspecies of B. rapa. Twelve identified GSLs were detected and were classified into three chemical groups based on patterns of GSL content and expression profiles of the BrMYBTFs. GSL content and BrMYBTF expression levels differed among genotypes, including B. rapa subspecies pekinensis, chinensis and rapa. BrMYB28.3, BrMYB51.1 and BrMYB122.2 positively regulated GSL content in 38 accessions. Furthermore, expression levels of BrMYB28s and BrMYB34.3 increased under most abiotic and biotic stress treatments. The three BrMYB51 paralogs also showed drastically increased expression levels after infection with Pectobacterium carotovorum. The results of the present study improve our understanding of the functional diversity of these 13 BrMYBTFs during the evolution of polyploid B. rapa.

Effects of Brassicaceae Isothiocyanates on Prostate Cancer

Despite the major progress made in the field of cancer biology, cancer is still one of the leading causes of mortality, and prostate cancer (PCa) is one of the most encountered malignancies among men. The effective management of this disease requires developing better anticancer agents with greater efficacy and fewer side effects. Nature is a large source for the development of chemotherapeutic agents, with more than 50% of current anticancer drugs being of natural origin. Isothiocyanates (ITCs) are degradation products from glucosinolates that are present in members of the family Brassicaceae. Although they are known for a variety of therapeutic effects, including antioxidant, immunostimulatory, anti-inflammatory, antiviral and antibacterial properties, nowadays, cell line and animal studies have additionally indicated the chemopreventive action without causing toxic side effects of ITCs. In this way, they can induce cell cycle arrest, activate apoptosis pathways, increase the sensitivity of resistant PCa to available chemodrugs, modulate epigenetic changes and downregulate activated signaling pathways, resulting in the inhibition of cell proliferation, progression and invasion-metastasis. The present review summarizes the chemopreventive role of ITCs with a particular emphasis on specific molecular targets and epigenetic alterations in in vitro and in vivo cancer animal models.

Concentrations of thiocyanate and goitrin in human plasma, their precursor concentrations in brassica vegetables, and associated potential risk for hypothyroidism

Brassica vegetables are common components of the diet and have beneficial as well as potentially adverse health effects. Following enzymatic breakdown, some glucosinolates in brassica vegetables produce sulforaphane, phenethyl, and indolylic isothiocyanates that possess anticarcinogenic activity. In contrast, progoitrin and indolylic glucosinolates degrade to goitrin and thiocyanate, respectively, and may decrease thyroid hormone production. Radioiodine uptake to the thyroid is inhibited by 194 μmol of goitrin, but not by 77 μmol of goitrin. Collards, Brussels sprouts, and some Russian kale (Brassica napus) contain sufficient goitrin to potentially decrease iodine uptake by the thyroid. However, turnip tops, commercial broccoli, broccoli rabe, and kale belonging to Brassica oleracae contain less than 10 μmol of goitrin per 100-g serving and can be considered of minimal risk. Using sulforaphane plasma levels following glucoraphanin ingestion as a surrogate for thiocyanate plasma concentrations after indole glucosinolate ingestion, the maximum thiocyanate contribution from indole glucosinolate degradation is estimated to be 10 μM, which is significantly lower than background plasma thiocyanate concentrations (40-69 μM). Thiocyanate generated from consumption of indole glucosinolate can be assumed to have minimal adverse risks for thyroid health.

Glucosinolates profile and antioxidant capacity of Romanian Brassica vegetables obtained by organic and conventional agricultural practices

The profile of glucosinolates in relation to the antioxidant capacity of five Brassica vegetables (Broccoli, Cauliflower, Kohlrabi, White and Red Cabbage) grown by organic and conventional agricultural practices in Transylvania region-Romania, were determined and compared. The qualitative and quantitative compositions of glucosinolates were determined by HPLC-PDA technique. The antioxidant capacity was comparatively determined by ABTS, DPPH, FRAP and Folin-Ciocalteu assays. The highest glucosinolates levels were found in the Broccoli samples grown under conventional practices (14.24 μmol/g dry weight), glucoraphanin, glucobrassicin and neo-glucobrassicin being the major components. The total glucosinolates content was similar in Kohlrabi and Cauliflower (4.89 and 4.84 μmol/g dry weight, respectively), the indolyl glucosinolates were predominant in Kohlrabi, while the aliphatic derivatives (sinigrin and glucoiberin) were major in Cauliflower. In Cabbage samples, the aliphatic glucosinolates were predominat against indolyl derivatives, glucoraphanin and glucoiberin being the main ones in Red Cabbage. The principal component analysis was applied to discriminate among conventional and organic samples and demonstrated non-overlaps between these two agricultural practices. Meanwhile it was shown that glucosinolates may represent appropriate molecular markers of Brassica vegetables, their antioxidant capacity being higher in organic crops, without significant differences among different Brassica varieties.

MYB transcription factors regulate glucosinolate biosynthesis in different organs of Chinese cabbage (Brassica rapa ssp. pekinensis)

In this study, we investigated the expression of seven MYB transcription factors (a total of 17 genes that included Dof1.1, IQD1-1, MYB28, MYB29, MYB34, MYB51, and MYB122 and their isoforms) involved in aliphatic and indolic glucosinolate (GSL) biosynthesis and analyzed the aliphatic and indolic GSL content in different organs of Chinese cabbage (Brassica rapassp. Pekinensis). MYB28 and MYB29 expression in the stem was dramatically different when compared with the levels in the other organs. MYB34, MYB122, MYB51, Dof1.1, and IQD1-1 showed very low transcript levels among different organs. HPLC analysis showed that the glucosinolates (GSLs) consisted of five aliphatic GSLs (progoitrin, sinigrin, glucoalyssin, gluconapin, and glucobrassicanapin) and four indolic GSLs (4-hydroxyglucobrassicin, glucobrassicin, 4-methoxygluco-brassicin, and neoglucobrassicin). Aliphatic GSLs exhibited 63.3% of the total GSLs content, followed by aromatic GSL (19.0%), indolic GSLs (10%), and unknown GSLs (7.7%) in different organs of Chinese cabbage. The total GSL content of different parts (ranked in descending order) was as follows: seed > flower > young leaves > stem > root > old leaves. The relationship between GSLs accumulation and expression of GSLs biosynthesis MYB TFs genes in different organs may be helpful to understand the mechanism of MYB TFs regulating GSL biosynthesis in Chinese cabbage.