The mechanism of deterioration of the glucosinolate-myrosynase system in radish roots during cold storage after harvest

Optimization of cultivar, germination time and extraction for radish sprout extract with high sulforaphene content

BACKGROUND

Cruciferous vegetable sprout has been highlighted as a promising functional material rich in bioactive compounds called isothiocyanates (ITCs) and it can be grown in very short periods in controlled indoor farms. However, because ITCs content depends on multiple factors such as cultivar, germination time and myrosinase activity, those variables need to be controlled during germination or extraction to produce functional materials enriched in ITCs. Sulforaphene (SFEN), an ITC found primarily in radishes (Raphanus sativus L.), exerts beneficial effects on obesity. However, the optimal germination and extraction conditions for radish sprout (RSP) to increase SFEN content remain unascertained, and the extract's anti-obesity effect has yet to be evaluated.

RESULTS

The present study found that the SFEN content was highest in purple radish sprout (PRSP) among the six cultivars investigated. Optimal SFEN content occurred after 2 days of PRSP germination (2 days PRSP). To maximize the dry matter yield, total ITCs and SFEN contents in RSP extract, we found the optimal conditions for extracting PRSP [27.5 °C, 60 min, 1:75.52 solute/solvent (w/v), no ascorbic acid] using response surface methodology. Consistent with high SFEN content, 2 days PRSP extract significantly outperformed 3 days or 4 days PRSP extract in inhibiting lipid accumulation in 3T3-L1 cells. Moreover, 2 days PRSP extract suppressed adipogenesis and lipogenesis-related protein expression.

CONCLUSION

Regarding the cultivar, germination time and extraction conditions, optimally produced PRSP extract contains high SFEN content and exerts anti-obesity effects. Thus, we suggest PRSP extract as a potent functional material for obesity prevention. © 2024 Society of Chemical Industry.

Micro-grinding-based production for sulforaphene-enriched radish seeds extract via facilitating glucosinolates-myrosinase reaction, and evaluation of its anti-adipogenic effects

Sulforaphene (SFEN), an isothiocyanate (ITC) abundant in radish (Raphanus sativus) seeds (RS), has many health benefits, including anti-obesity effects. SFEN content is affected by multiple factors during processing, such as glucoraphenin (GLE) (the precursor of SFEN) availability, myrosinase (essential for conversion from GLE to SFEN) activity, and SFEN stability. We examined the physiochemical-properties and anti-adipogenic effects of SFEN-enriched RSE produced by two processes, roasting and micro-grinding. The roasting process lowered SFEN content and myrosinase activity over 50 °C. However, among micro-grinding conditions, smaller particle size (#2 grind, ≈11.31 μm) more effectively increased SFEN content in RS compared to larger particles (#1 grind, ≈ 179.50 μm) by accelerating available GLE and myrosinase release from RS. Grind #2 also effectively inhibited the adipogenesis of 3T3-L1 pre-adipocytes compared to #1. Thus, micro-grinding can be suggested for producing SFEN-enriched RSE with anti-adipogenic activity as a functional material for obesity prevention or treatment.

Sulforaphene Inhibits Periodontitis through Regulating Macrophage Polarization via Upregulating Dendritic Cell Immunoreceptor

Periodontitis is one of the most prevalent chronic inflammatory diseases that may eventually lead to the loss of teeth. Macrophage polarization plays an important role in the development of periodontitis, and several naturally occurring food compounds have recently been reported to regulate macrophage polarization. In this study, we aimed to investigate the therapeutic potential of sulforaphene (SFE) in macrophage polarization and its impact on periodontitis. Through in vitro and in vivo experiments, our study demonstrated that SFE effectively inhibits M1 polarization while promoting M2 polarization, ultimately leading to the suppression of periodontitis. Transcriptome sequencing showed that SFE significantly upregulated the expression of dendritic cell immunoreceptor (DCIR, also known as CLEC4A2). We further validated the crucial role of DCIR in macrophage polarization through knockdown and overexpression experiments and demonstrated that SFE regulates macrophage polarization by upregulating DCIR expression. In summary, the results of this study suggest that SFE can regulate macrophage polarization and inhibit periodontitis. Moreover, this research identified DCIR (dendritic cell immunoreceptor) as a potential novel target for regulating macrophage polarization. These findings provide new insights into the treatment of periodontitis and other immune-related diseases.

Effects of Glucosinolate-Enriched Red Radish (Raphanus sativus) on In Vitro Models of Intestinal Microbiota and Metabolic Syndrome-Related Functionalities

The gut microbiota profile is determined by diet composition, and therefore this interaction is crucial for promoting specific bacterial growth and enhancing the health status. Red radish (Raphanus sativusL.) contains several secondary plant metabolites that can exert a protective effect on human health. Recent studies have shown that radish leaves have a higher content of major nutrients, minerals, and fiber than roots, and they have garnered attention as a healthy food or supplement. Therefore, the consumption of the whole plant should be considered, as its nutritional value may be of greater interest. The aim of this work is to evaluate the effects of glucosinolate (GSL)-enriched radish with elicitors on the intestinal microbiota and metabolic syndrome-related functionalities by using an in vitro dynamic gastrointestinal system and several cellular models developed to study the GSL impact on different health indicators such as blood pressure, cholesterol metabolism, insulin resistance, adipogenesis, and reactive oxygen species (ROS). The treatment with red radish had an influence on short-chain fatty acids (SCFA) production, especially on acetic and propionic acid and many butyrate-producing bacteria, suggesting that consumption of the entire red radish plant (leaves and roots) could modify the human gut microbiota profile toward a healthier one. The evaluation of the metabolic syndrome-related functionalities showed a significant decrease in the gene expression of endothelin, interleukin IL-6, and cholesterol transporter-associated biomarkers (ABCA1 and ABCG5), suggesting an improvement of three risk factors associated with metabolic syndrome. The results support the idea that the use of elicitors on red radish crops and its further consumption (the entire plant) may contribute to improving the general health status and gut microbiota profile.

High-level and reusable preparation of sulforaphane by yeast cells expressing myrosinase

Myrosinase is a key tool for the fast and efficient preparation of sulforaphane which is one of the prominent natural ingredients found in brassicaceous vegetables. Here, the glucoraphanin-hydrolyzing activity of a Yarrowia lipolytica 20-8 harboring myrosinase reached 73.28 U/g dry cell weight, indicating that it had a potential application in sulforaphane preparation from glucoraphanin. An efficient and reusable process for sulforaphane preparation via myrosinase produced by Y. lipolytica 20-8 was constructed. In detail, as high as 10.32 mg sulforaphane could be produced from 1 g broccoli seed under the reaction of 40 U yeast whole-cell catalyst within 15 min with the conversion efficiency of 99.86%. Moreover, when the yeast whole-cell catalyst was reused 7 and 10 times, as high as 92.53% and 87.56% of sulforaphene yield of the initial level could be retained, respectively. Therefore, this yeast whole-cell is a potent biocatalyst for the efficient and reusable preparation of sulforaphane.

The Disturbance of the Antioxidant System Results in Internal Blue Discoloration of Postharvest Cherry Radish (Raphanus sativus L. var. radculus pers) Roots

Internal blue discoloration in cherry radish (Raphanus sativus L. var. radculus pers) roots can appear after harvest. The antioxidant system and content of reactive oxygen species (ROS) will affect the blue discoloration. Currently, the reason for the blue discoloration is not yet clear. In order to reveal the mechanism of the blue discoloration of cherry radish, we selected the blue discolored cherry radish as the research object and the white cherry radish as the control. The difference in the antioxidant system between them were compared, including related enzymes and non-enzymatic antioxidants in this system. Meanwhile, the changes in the contents of 4-hydroxyglucobrassicin as a precursor substance and ROS were compared. The results showed that the activities of typical antioxidant enzymes decreased and the cycle of Glutathione peroxidase (GPX) and Ascorbic acid-Glutathione (ASA-GSH) was disturbed, leading to the reduction of antioxidant effect and the failure of timely and effective decomposition of superoxide anions (O₂^•-) and hydrogen peroxide (H₂O₂). In addition, the elevated level of O₂^•- and H₂O₂ led to the disorder of the antioxidant system, while the 4-hydroxybrassinoside was oxidized under the catalysis of peroxidase (POD) and eventually led to the internal blue discoloration in cherry radish. These results can provide a theoretical basis for solving the blue discoloration problem.

The glucosinolate profiles of Brassicaceae vegetables responded differently to quick-freezing and drying methods

Glucosinolates (GLS) are bioactive compounds found in Brassicaceae vegetables. Industrial food processing treatments, such as blanching, quick-freezing (QF), vacuum freeze-drying (VFD), vacuum-drying (VD) and oven-drying (OD), significantly affect the degradation and ingestion of GLS. Here, the effects of these treatments, followed by boiling, on the GLS content and mimicking ingestion level of isothiocyanate from Brassicaceae vegetables (broccoli, cauliflower, white and red cabbages, Chinese and baby cabbages, white and red radish roots) were investigated. The results showed that blanching-QF maintained or increased the GLS content as well as preserved the ingestion level of isothiocyanate, an optimum treatment for GLS preservation. Blanching-VFD was recommended for these vegetables, while blanching-VD and blanching-OD caused relatively high GLS losses and low isothiocyanate production. Additionally, stabilities of individual GLS during processing rely on their chemical structures and species. Generally, aliphatic GLS from Brassicaceae showed lower loss than indole GLS, indicating differences in their stabilities during processing.

Evaluation of Postharvest Senescence of Broccoli via Hyperspectral Imaging

Fresh fruit and vegetables are invaluable for human health; however, their quality often deteriorates before reaching consumers due to ongoing biochemical processes and compositional changes. We currently lack any objective indices which indicate the freshness of fruit or vegetables resulting in limited capacity to improve product quality eventually leading to food loss and waste. In this conducted study, we hypothesized that certain proteins and compounds, such as glucosinolates, could be used as one potential indicator to monitor the freshness of broccoli following harvest. To support our study, glucosinolate contents in broccoli based on HPLC measurement and transcript expression of glucosinolate biosynthetic genes in response to postharvest stresses were evaluated. We found that the glucosinolate biosynthetic pathway coincided with the progression of senescence in postharvest broccoli during storage. Additionally, we applied machine learning-based hyperspectral image (HSI) analysis, unmixing, and subpixel target detection approaches to evaluate glucosinolate level to detect postharvest senescence in broccoli. This study provides an accessible approach to precisely estimate freshness in broccoli through machine learning-based hyperspectral image analysis. Such a tool would further allow significant advancement in postharvest logistics and bolster the availability of high-quality, nutritious fresh produce.

Influence of sequential exogenous pretreatment and contact ultrasound-assisted air drying on the metabolic pathway of glucoraphanin in broccoli florets

In this investigation, the combinations of exogenous pretreatment (melatonin or vitamin C) and contact ultrasound-assisted air drying were utilized to dry broccoli florets. To understand the influences of the studied dehydration methods on the conversion of glucoraphanin to bioactive sulforaphane in broccoli, various components (like glucoraphanin, sulforaphane, myrosinase, etc.) and factors (temperature and moisture) involved in the metabolism pathway were analyzed. The results showed that compared with direct air drying, the sequential exogenous pretreatment and contact ultrasound drying shortened the drying time by 19.0-22.7%. Meanwhile, contact sonication could promote the degradation of glucoraphanin. Both melatonin pretreatment and vitamin C pretreatment showed protective effects on the sulforaphane content and myrosinase activity during the subsequent drying process. At the end of drying, the sulforaphane content in samples dehydrated by the sequential melatonin (or vitamin C) pretreatment and ultrasound-intensified drying was 14.4% (or 26.5%) higher than only air-dried samples. The correlation analysis revealed that the exogenous pretreatment or ultrasound could affect the enzymatic degradation of glucoraphanin and the generation of sulforaphane through weakening the connections of sulforaphane-myrosinase, sulforaphane-VC, and VC-myrosinase. Overall, the reported results can enrich the biochemistry knowledge about the transformation of glucoraphanin to sulforaphane in cruciferous vegetables during drying, and the combined VC/melatonin pretreatment and ultrasound drying is conducive to protect bioactive sulforaphane in dehydrated broccoli.

Adding Far-Red to Red, Blue Supplemental Light-Emitting Diode Interlighting Improved Sweet Pepper Yield but Attenuated Carotenoid Content

Supplemental interlighting is commonly used in modern greenhouses to improve light deficiency, but the light spectrum affects fruit quality and color change. This study aimed to analyze the effect of interlighting with red, blue, and additional far-red light on the fruit qualities and carotenoid contents of red and yellow sweet peppers (Capsicum annuum L.). Three light treatments were applied: natural light (NL), NL with red + blue LED interlighting (71 μmol m^-2 s^-1) (RB), and RB with far-red light (55 μmol m^-2 s^-1) (RBFR). Ascorbic acid, free sugars, and individual carotenoid content were quantified with HPLC analysis. Fruits were sampled on 2020.11.14 (Group 1) and 2021.01.03 (Group 2) from the plants grown under average light intensities of 335.9 and 105.6 μmol m^-2 s^-1, respectively. In the overall period, total yields in RB and RBFR were 22 and 33% higher than those in NL in red fruits and 2 and 21% higher in yellow fruits, respectively. In both colored fruits, ascorbic acid, total soluble sugar, and carotenoid content were higher in RB and RBFR than NL. In Group 1, ascorbic acid and total soluble sugar were significantly different between RB and RBFR only in red fruits. In Group 2, ascorbic acids in red and yellow fruits were 9 and 3% higher in RBFR than RB but total soluble sugars were 4 and 2% lower, respectively. Carotenoid contents in red and yellow fruits were 3.0- and 2.1-fold higher in RB and 2.0- and 1.4-fold higher in RBFR than those in NL, respectively. In this study, interlighting had a significant impact on fruit quality in Group 2, mainly due to the increase in the ratio of interlighting to total light by seasonal changes. In particular, red and yellow fruit yields were 9% and 19% higher in RBFR than RB, but carotenoid contents were 26 to 9% lower, respectively. This result exhibited that additional far-red lighting has a trade-off relationship between fruit yield and carotenoid content. Thus, it is necessary to provide an adequate light spectrum according to a specific cultivation purpose, such as improving yield or accumulating plastids in fruits.

Phytonutrients and Metabolism Changes in Topped Radish Root and Its Detached Leaves during 1 °C Cold Postharvest Storage

Glucosinolates, lipid-soluble vitamins E and K contents, primary metabolites and plant hormones were analyzed from topped radish root and detached leaf during storage at 1 °C. The topped root was analyzed at 0, 5, 15, 30, and 90 days after storage while the detached leaf was analyzed at 0, 5, 15, 30, and 45 days in an airtight storage atmosphere environment. The results showed that aliphatic glucosinolates were gradually decreased in leaf but not in root. There was a highly significant correlation between tryptophan and 4-methoxyindoleglucobrassicin in both tissues (r = 0.922, n = 10). There was no significant difference in vitamins E and K in leaf and root during storage. Plant hormones partially explained the significantly changed metabolites by tissue and time, which were identified during cold storage. Phenylalanine, lysine, tryptophan, and myo-inositol were the most important biomarkers that explained the difference in leaf and root tissue during cold storage. The most different metabolism between leaf and root tissue was starch and sucrose metabolism. Therefore, different postharvest technology or regimes should be applied to these tissues.

Inhibitory mechanism of low-oxygen-storage treatment in postharvest internal bluing of radish (Raphanus sativus) roots

Oxidative stress in radish roots causes internal blue discoloration and decreases vegetable quality. Accordingly, the effects of different oxygen concentration treatment on this coloration during storage was investigated; 4-hydroxyglucobrassicin content (a precursor of the blue component); the reactive oxygen species (ROS) superoxide (O₂^-) and hydrogen peroxide (H₂O₂); the antioxidants ascorbic acid (AsA) and glutathione (GSH); and the activities and gene expression levels of the enzymes catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), were monitored under normal and low-oxygen conditions. The results indicated that packaging radish roots under 10% O₂ prevents blue discoloration by decreasing the activity and expression of the oxidant enzyme POD, increasing the levels of antioxidant and reducing substances, and upregulating antioxidant enzymes, all of which act to decrease the generation of ROS (O^2- and H₂O₂).

Preparation of Sulforaphene from Radish Seed Extracts with Recombinant Food-Grade Yarrowia lipolytica Harboring High Myrosinase Activity

Sulforaphene prepared from glucoraphenin by myrosinase is one of the main active ingredients of radish, which has various biological activities and brilliant potential for food and pharmaceutical applications. In this paper, a recombinant food-grade yeast transformant 20-8 with high-level myrosinase activity was constructed by over-expressing a myrosinase gene from Arabidopsis thaliana in Yarrowia lipolytica. The highest myrosinase activity produced by the transformant 20-8 reached 44.84 U/g dry cell weight when it was cultivated in a 10 L fermentor within 108 h. Under the optimal reaction conditions, 6.1 mg of sulforaphene was yielded from 1 g of radish seeds under the catalysis of the crude myrosinase preparation (4.95 U) at room temperature within 1.5 h. What is more is that when the whole yeast cells harboring myrosinase activity were reused 10 times, the sulforaphene yield still reached 92.53% of the initial level. Therefore, this efficient approach has broad application prospects in recyclable and large-scale preparation of sulforaphene.

Transcriptome and metabolome profiling to elucidate mechanisms underlying the blue discoloration of radish roots during storage

The internal blue discoloration of radish roots (Raphanus sativus) during storage affects their quality. We here performed transcriptome and metabolome profiling to investigate the mechanisms underlying the bluing of radish roots during storage. On comparing white radish (WR) and blue radish (BR), we identified 14,171 differentially expressed genes (upregulated: 7,383, downregulated: 6,788) and 145 differentially accumulated metabolites (upregulated: 117, downregulated: 28). Functional annotation analysis and metabolome profiling revealed that the blue discoloration of radish roots was promoted by high content of glucosinolates, oxidation system (ROS, CAT, POD) or low reduction system (GSH, GPX, APX, GST, ASA). Our results provide new insights into the underlying metabolic causes of the blue discoloration of radish roots and report candidate genes and metabolites involved in blue compound biosynthesis.

Comparison of blue discoloration in radish root among different varieties and blue pigment stability analysis

The internal blue discoloration of radish root after harvest is a physiological phenomenon that decreases the radish quality. Internal blue discoloration in the roots of 16 varieties of Chinese radish along with the stability of blue pigment under different light, pH, and temperature conditions were investigated. Among the varieties LB05-244 and LB05-240 displayed the greatest degrees of discoloration, while the Piton and Dense radishes exhibited the lowest degrees of discoloration. The light and pH conditions along with the storage temperature affected the pigment stability. The degradation of blue pigment occurred faster under blue light than under green, red, and white light and darkness. Blue pigment degraded fastest at pH values of 13 and 1. The blue pigments in radish exhibited thermal instability, with complete degradation occurring in 5 or 10 min at 90 or 100 °C, respectively. In conclusion, variety affected the discoloration. The pigment exhibited light, pH and thermal instability.

Human, Animal and Plant Health Benefits of Glucosinolates and Strategies for Enhanced Bioactivity: A Systematic Review

Glucosinolates (GSs) are common anionic plant secondary metabolites in the order Brassicales. Together with glucosinolate hydrolysis products (GSHPs), they have recently gained much attention due to their biological activities and mechanisms of action. We review herein the health benefits of GSs/GSHPs, approaches to improve the plant contents, their bioavailability and bioactivity. In this review, only literature published between 2010 and March 2020 was retrieved from various scientific databases. Findings indicate that these compounds (natural, pure, synthetic, and derivatives) play an important role in human/animal health (disease therapy and prevention), plant health (defense chemicals, biofumigants/biocides), and food industries (preservatives). Overall, much interest is focused on in vitro studies as anti-cancer and antimicrobial agents. GS/GSHP levels improvement in plants utilizes mostly biotic/abiotic stresses and short periods of phytohormone application. Their availability and bioactivity are directly proportional to their contents at the source, which is affected by methods of food preparation, processing, and extraction. This review concludes that, to a greater extent, there is a need to explore and improve GS-rich sources, which should be emphasized to obtain natural bioactive compounds/active ingredients that can be included among synthetic and commercial products for use in maintaining and promoting health. Furthermore, the development of advanced research on compounds pharmacokinetics, their molecular mode of action, genetics based on biosynthesis, their uses in promoting the health of living organisms is highlighted.

The glucosinolates and their bioactive derivatives in Brassica: a review on classification, biosynthesis and content in plant tissues, fate during and after processing, effect on the human organism and interaction with the gut microbiota

The present study is a systematic review of the scientific literature reporting content, composition and biosynthesis of glucosinolates (GLS), and their derivative compounds in Brassica family. An amended classification of brassica species, varieties and their GLS content, organized for the different plant organs and in uniformed concentration measure unit, is here reported for the first time in a harmonized and comparative manner. In the last years, the studies carried out on the effect of processing on vegetables and the potential benefits for human health has increased rapidly and consistently the knowledge on the topic. Therefore, there was the need for an updated revision of the scientific literature of pre- and post-harvest modifications of GLS content, along with the role of gut microbiota in influencing their bioavailability once they are ingested. After analyzing and standardizing over 100 articles and the related data, the highest GLS content in Brassica, was declared in B. nigra (L.) W. D. J. Koch (201.95 ± 53.36 µmol g^-1), followed by B. oleracea Alboglabra group (180.9 ± 70.3 µmol g^-1). The authors also conclude that food processing can influence significantly the final content of GLS, considering the most popular methods: boiling, blanching, steaming, the latter can be considered as the most favorable to preserve highest level of GLS and their deriviatives. Therefore, a mild-processing strategic approach for GLS or their derivatives in food is recommended, in order to minimize the loss of actual bioactive impact. Finally, the human gut microbiota is influenced by Brassica-rich diet and can contribute in certain conditions to the increasing of GLS bioavailability but further studies are needed to assess the actual role of microbiomes in the bioavailability of healthy glucosinolate derivatives.

Isothiocyanates and Glucosinolates from Sisymbrium officinale (L.) Scop. ("the Singers' Plant"): Isolation and in Vitro Assays on the Somatosensory and Pain Receptor TRPA1 Channel

Sisymbrium officinale (L.) Scop. is a wild common plant of the Brassicaceae family. It is known as “the singers’ plant” for its traditional use in treating aphonia and vocal disability. Despite its wide use in herbal preparations, the molecular mechanism of action of S. officinale extracts is not known. The plant is rich in glucosinolates and isothiocyanates, which are supposed to be its active compounds. Some members of this family, in particular allylisothiocyanate, are strong agonists of the transient receptor potential ankyrin 1 (TRPA1) channel, which is involved in the somatosensory perception of pungency as well as in the nociception pathway of inflammatory pain. This study aims to isolate the glucosinolates and isothiocianates from fresh S. officinale to identify the major components and test their activity in in vitro assays with a cloned TRPA1 channel. Samples of cultivated S. officinale have been extracted and the active compounds isolated by column chromatography, HPLC and PTLC. The main components glucoputranjivin, isopropylisothiocyanate and 2-buthylisothiocianate have been tested on TRPA1. The glucosinolates glucoputranjivin and sinigrin turned out to be inactive, while isopropylisothiocyanate and 2-buthylisothiocyanate are potent agonists of TRPA1, with an EC₅₀ in the range of the high potency natural agonists identified so far for this somatosensory channel.

Liquid chromatography-high resolution mass spectrometry for the analysis of phytochemicals in vegetal-derived food and beverages

The recent years witnessed a change in the perception of nutrition. Diet does not only provide nutrients to meet the metabolic requirements of the body, but it also constitutes an active way for the consumption of compounds beneficial for human health. Fruit and vegetables are an excellent source of such compounds, thus the growing interest in characterizing phytochemical sources, structures and activities. Given the interest for phytochemicals in food, the development of advanced and suitable analytical techniques for their identification is fundamental for the advancement of food research. In this review, the state of the art of phytochemical research in food plants is described, starting from sample preparation, throughout extract clean-up and compound separation techniques, to the final analysis, considering both qualitative and quantitative investigations. In this regard, from an analytical point of view, fruit and vegetable extracts are complex matrices, which greatly benefit from the use of modern hyphenated techniques, in particular from the combination of high performance liquid chromatography separation and high resolution mass spectrometry, powerful tools which are being increasingly used in the recent years. Therefore, selected applications to real samples are presented and discussed, in particular for the analysis of phenols, polyphenols and phenolic acids. Finally, some hot points are discussed, such as waste characterization for high value-compounds recovery and the untargeted metabolomics approach.