Endogenous Circadian Rhythms in Polyphenolic Composition Induce Changes in Antioxidant Properties in Brassica Cultivars

Organic fertilizer mitigated the oxidative stress of tomato induced by nanoplastics through affecting rhizosphere soil microorganisms and bacteriophage functions

Nanoplastics (NPs), which are widely present in agricultural soils, are difficult to remove and are potentially harmful to plant growth and development. However, few studies have focused on how to mitigation the oxidative stress in plants induced by soil NPs exposure. Therefore, in this study, the effects of organic and chemical fertilizers on the oxidative stress of tomato under exposure to polystyrene nanoplastics (PS-NPs) in soil were investigated. Compared with chemical fertilizer under exposure to PS-NPs, the organic fertilizer reduced the reactive oxygen species (ROS) content by 25.63 % and the H2O2 content by 34.58 % in tomato stems, whereas no significant effects were observed with respect to the amount of PS-NP internalized in tomato. Additionally, organic fertilizer increased the accumulation of the phytohormones salicylic acid (SA) and abscisic acid (ABA) by 76.53 % and 22.54 %, respectively, and these factors are key for reducing the ROS and H2O2 contents in stems. In the rhizosphere microbiome of organic fertilizer group under exposure to PS-NPs, enrichment in Actinomycetes and an increased abundance of terpenoids and polyketides metabolism were the main factors affecting the accumulation of ABA and SA. Moreover, bacteriophage activity in the rhizosphere indirectly contributed to the increase in this function. These changes ultimately resulted in a reduction in oxidative stress in tomato stems and protected tomato growth. The results of this study will provide a better understanding of the interaction between plants and nanoplastics in soil and provide a new reference for alleviating the oxidative stress caused by nanoplastics in plants.

Determination of Morphogenetic and Diurnal Variability in Phenolic and Flavonoid Content of Echinacea purpurea (L.) Moench: A Potential Source of Natural Anioxidants

Echinacea purpurea (L.) Monech has a diverse range of phytochemicals, including flavonoids, polyphenols, phenolic acids, alkylamides, and terpenoids. Phenolic and flavonoid substances derived from the leaves and flowers have been used for treatment of illness. The aim of this study to evaluate the polyphenolic components of the flowers and leaves of E. purpurea, along with the diurnal variations and the morphological differences. Two-year-old in full bloom flowers and leaves were harvested at different times of the day (6:00 am, 9:00 am, 12:00 am, 03:00 pm, 06:00 pm, 09:00 pm). The water and methanol extracts prepared from these samples to determine total phenolic, total flavonoid and phenolic compound contents. The experiment was established in randomized complete block design with three factors and three replications. The highest total phenolic content was observed in flowers with methanol extract (157.91 ± 0.32 mg QE/g dry extract) at 09.00 a.m. Also the highest total flavonoid content was observed in leaves with methanol extract at 09.00 a.m (80.12 ± 0.16 mg QE/g dry extract). Chlorogenic acid (19.1 ± 0.83 mg/g methanol extract) and caffeic acid (13.2 ± 0.58 mg/g methanol extract) were identified as the predominant phenolic acids. The peak concentrations of these phenolic acids were observed at 6:00 a.m, followed by a gradual decline throughout the subsequent hours of the day. Findings emphasize the importance of harvesting E. purpurea at the optimal time to maximize antioxidant capacity. This study provides valuable new information on morphogenetic and diurnal variation of phenolic and flavonoid content for drug and pharmaceutical raw material production.

Unlocking Nature's Rhythms: Insights into Secondary Metabolite Modulation by the Circadian Clock

Plants, like many other living organisms, have an internal timekeeper, the circadian clock, which allows them to anticipate photoperiod rhythms and environmental stimuli to optimally adjust plant growth, development, and fitness. These fine-tuned processes depend on the interaction between environmental signals and the internal interactive metabolic network regulated by the circadian clock. Although primary metabolites have received significant attention, the impact of the circadian clock on secondary metabolites remains less explored. Transcriptome analyses revealed that many genes involved in secondary metabolite biosynthesis exhibit diurnal expression patterns, potentially enhancing stress tolerance. Understanding the interaction mechanisms between the circadian clock and secondary metabolites, including plant defense mechanisms against stress, may facilitate the development of stress-resilient crops and enhance targeted management practices that integrate circadian agricultural strategies, particularly in the face of climate change. In this review, we will delve into the molecular mechanisms underlying circadian rhythms of phenolic compounds, terpenoids, and N-containing compounds.

Integrated Metabolomic-Transcriptomic Analyses of Flavonoid Accumulation in Citrus Fruit under Exogenous Melatonin Treatment

The flavonoids in citrus fruits are crucial physiological regulators and natural bioactive products of high pharmaceutical value. Melatonin is a pleiotropic hormone that can regulate plant morphogenesis and stress resistance and alter the accumulation of flavonoids in these processes. However, the direct effect of melatonin on citrus flavonoids remains unclear. In this study, nontargeted metabolomics and transcriptomics were utilized to reveal how exogenous melatonin affects flavonoid biosynthesis in "Bingtangcheng" citrus fruits. The melatonin treatment at 0.1 mmol L-1 significantly increased the contents of seven polymethoxylated flavones (PMFs) and up-regulated a series of flavonoid pathway genes, including 4CL (4-coumaroyl CoA ligase), FNS (flavone synthase), and FHs (flavonoid hydroxylases). Meanwhile, CHS (chalcone synthase) was down-regulated, causing a decrease in the content of most flavonoid glycosides. Pearson correlation analysis obtained 21 transcription factors co-expressed with differentially accumulated flavonoids, among which the AP2/EREBP members were the most numerous. Additionally, circadian rhythm and photosynthesis pathways were enriched in the DEG (differentially expressed gene) analysis, suggesting that melatonin might also mediate changes in the flavonoid biosynthesis pathway by affecting the fruit's circadian rhythm. These results provide valuable information for further exploration of the molecular mechanisms through which melatonin regulates citrus fruit metabolism.

Ozone control as a novel method to improve health-promoting bioactive compounds in red leaf lettuce (Lactuca sativa L.)

In this study, we determined the short-term effects of ozone exposure on the growth and accumulation of bioactive compounds in red lettuce leaves grown in a controlled environment plant factory with artificial light, also known as a vertical farm. During cultivation, twenty-day-old lettuce (Lactuca sativa L. var. Redfire) seedlings were exposed to 100 and 200 ppb of ozone concentrations for 72 h. To find out how plants react to ozone and light, complex treatments were done with light and ozone concentrations (100 ppb; 16 h and 200 ppb; 24 h). Ozone treatment with 100 ppb did not show any significant difference in shoot fresh weight compared to that of the control, but the plants exposed to the 200 ppb treatment showed a significant reduction in fresh weight by 1.3 fold compared to the control. The expression of most genes in lettuce plants exposed to 100 and 200 ppb of ozone increased rapidly after 0.5 h and showed a decreasing trend after reaching a peak. Even when exposed to a uniform ozone concentration, the pattern of accumulating bioactive compounds such as total phenolics, antioxidant capacity and total flavonoids varied based on leaf age. At a concentration of 200 ppb, a greater accumulation was found in the third (older) leaf than in the fourth leaf (younger). The anthocyanin of lettuce plants subjected to 100 and 200 ppb concentrations increased continuously for 48 h. Our results suggest that ozone control is a novel method that can effectively increase the accumulation of bioactive compounds in lettuce in a plant factory.

Metabolic diversity in a collection of wild and cultivated Brassica rapa subspecies

Brassica rapa (B. rapa) and its subspecies contain many bioactive metabolites that are important for plant defense and human health. This study aimed at investigating the metabolite composition and variation among a large collection of B. rapa genotypes, including subspecies and their accessions. Metabolite profiling of leaves of 102 B. rapa genotypes was performed using ultra-performance liquid chromatography coupled with a photodiode array detector and quadrupole time-of-flight mass spectrometry (UPLC-PDA-QTOF-MS/MS). In total, 346 metabolites belonging to different chemical classes were tentatively identified; 36 out of them were assigned with high confidence using authentic standards and 184 were those reported in B. rapa leaves for the first time. The accumulation and variation of metabolites among genotypes were characterized and compared to their phylogenetic distance. We found 47 metabolites, mostly representing anthocyanins, flavonols, and hydroxycinnamic acid derivatives that displayed a significant correlation to the phylogenetic relatedness and determined four major phylometabolic branches; 1) Chinese cabbage, 2) yellow sarson and rapid cycling, 3) the mizuna-komatsuna-turnip-caitai; and 4) a mixed cluster. These metabolites denote the selective pressure on the metabolic network during B. rapa breeding. We present a unique study that combines metabolite profiling data with phylogenetic analysis in a large collection of B. rapa subspecies. We showed how selective breeding utilizes the biochemical potential of wild B. rapa leading to highly diverse metabolic phenotypes. Our work provides the basis for further studies on B. rapa metabolism and nutritional traits improvement.

Mutations that alter Arabidopsis flavonoid metabolism affect the circadian clock

Flavonoids are a well-known class of specialized metabolites that play key roles in plant development, reproduction, and survival. Flavonoids are also of considerable interest from the perspective of human health, as both phytonutrients and pharmaceuticals. RNA sequencing analysis of an Arabidopsis null allele for chalcone synthase (CHS), which catalyzes the first step in flavonoid metabolism, has uncovered evidence that these compounds influence the expression of genes associated with the plant circadian clock. Analysis of promoter-luciferase constructs further showed that the transcriptional activity of CCA1 and TOC1, two key clock genes, is altered in CHS-deficient seedlings across the day/night cycle. Similar findings for a mutant line lacking flavonoid 3'-hydroxylase (F3'H) activity, and thus able to synthesize mono- but not dihydroxylated B-ring flavonoids, suggests that the latter are at least partially responsible; this was further supported by the ability of quercetin to enhance CCA1 promoter activity in wild-type and CHS-deficient seedlings. The effects of flavonoids on circadian function were also reflected in photosynthetic activity, with chlorophyll cycling abolished in CHS- and F3'H-deficient plants. Remarkably, the same phenotype was exhibited by plants with artificially high flavonoid levels, indicating that neither the antioxidant potential nor the light-screening properties of flavonoids contribute to optimal clock function, as has recently also been demonstrated in animal systems. Collectively, the current experiments point to a previously unknown connection between flavonoids and circadian cycling in plants and open the way to better understanding of the molecular basis of flavonoid action.

Bacterial-Assisted Extraction of Bioactive Compounds from Cauliflower

The market for nutraceutical molecules is growing at an impressive pace in all Western countries. A convenient source of bioactive compounds is found in vegetable waste products, and their re-use for the recovery of healthy biomolecules would increase the sustainability of the food production system. However, safe, cheap, and sustainable technologies should be applied for the recovery of these beneficial molecules, avoiding the use of toxic organic solvents or expensive equipment. The soil bacterium Bacillus subtilis is naturally endowed with several enzymes targeting complex vegetable polymers. In this work, a raw bacterial culture supernatant was used to assist in the extraction of bioactives using isothermal pressurization cycles. Besides a wild-type Bacillus subtilis strain, a new strain showing increased secretion of cellulases and xylanases, pivotal enzymes for the digestion of the plant cell wall, was also used. Results indicate that the recovery of compounds correlates with the amount of cellulolytic enzymes applied, demonstrating that the pretreatment with non-purified culture broth effectively promotes the release of bioactives from the vegetable matrix. Therefore, this approach is a valid and sustainable procedure for the recovery of bioactive compounds from food waste.

Mycorrhizal fungi regulate daily rhythm of circadian clock in trifoliate orange under drought stress

The circadian rhythm of plants is associated with stress responses; however, it is not clear whether increased host plant drought tolerance by arbuscular mycorrhizal fungi (AMF) is associated with changes in the circadian clock. The present study aimed to analyze the effect of Funneliformis mosseae (Nicol. & Gerd.) Schüßler & Walker on the circadian clock gene expression patterns in trifoliate orange (Poncirus trifoliata L. Raf.) along with gas exchange, abscisic acid (ABA) levels and antioxidant enzyme gene expression under well-watered (WW) and drought stress (DS) conditions. Plant growth, net photosynthetic rate, stomatal conductance and ABA levels were significantly higher in AMF- than in non-AMF-inoculated plants regardless of soil water regimes. Six circadian clock genes, including PtPRR7, PtLHY, PtCCA1, PtGI, PtPIF3 and PtSRR1, were identified and showed rhythmic expression patterns over the course of the day. The AMF inoculation reduced the expression of most circadian clock genes in different time periods. However, AMF treatment significantly increased PtPRR7 and PtGI expression at 5:00 p.m. under WW and DS conditions, PtLHY expression at 1:00 a.m. and PtSRR1 expression at 9:00 p.m. At 1:00 a.m., AMF inoculation up-regulated the expression of the circadian clock genes PtPRR7, PtCCA1, PtLHY and PtPIF3 and the antioxidant enzyme genes PtFe-SOD, PtMn-SOD, PtCu/Zn-SOD, PtPOD and PtCAT1. Correlation analysis revealed that these changes in circadian clock gene expression were associated with antioxidant enzyme gene expression, root ABA and gas exchange. We concluded that mycorrhizal fungi have the ability to regulate the daily rhythm of the circadian clock in trifoliate orange plants in response to drought.

Plant Responses Underlying Timely Specialized Metabolites Induction of Brassica Crops

A large subset of plant stress-signaling pathways, including those related with chemical defense production, exhibit diurnal or circadian oscillations. However the extent to which diurnal or circadian time influences the stress mediated accumulation of plant specialized metabolites remains largely unknown. Because plant responses to physical stress (e.g., wounding) is considered a common component of mounting a response against a broad range of environmental stresses, including herbivory, we have utilized mechanical wounding as the stress stimulus to determine the direct contribution of time of day on the induced defenses of Brassica crops. We analyzed glucosinolates (GSLs) from leaves of broccoli (Brassica oleracea) and turnip greens (Brassica rapa) following exposure to mechanical wounding at dawn (ZT0), mid-day (ZT4), and dusk (ZT8). Several GSLs differentially accumulated and their changes depended upon the time of day at wounding was performed. This response varied considerably between species. In a parallel experiment, we investigated whether diurnal activation of Brassica phytochemicals in response to wounding might prime plants against herbivore attack. Results showed that maximal response of plant chemical defense against larvae of the generalist pest Mamestra brassicae occurred at ZT0 in broccoli and ZT8 in turnip greens. Metabolome analysis for global trends of time dependent compounds showed that sulfur-containing phytochemicals, GSL hydrolysis products, auxin-signaling components, and other metabolites activators of plant disease resistance (nicotinamide and pipecolate) had important contributions to the responses of M. brassicae feeding behavior in broccoli at morning. Overall, the findings in this study highlight a significant role for time of day in the wound stress responsive metabolome, which can in turn affect plant-herbivore interactions.

Daily dynamics of intermediate metabolite profiles lead to time-dependent phenylethanoid glycosides production in Scrophularia striata during the day/night cycle

Phenylethanoid glycosides (PhGs) are important medicinal compounds found in Scrophularia striata, one of the plant species native to Iran. Since almost all aspects of plant life are controlled by night/light cycle, studying its relationship to valuable plant metabolites production will help us to determine the right time for their extraction. Therefore, the aim of this investigation is to figure out whether the diel light oscillations control PhGs production and how it relates to daily changes in upstream metabolic reactions and circadian clock in S. striata. For this, daily rhythms of metabolic pathways were examined every 4 h during a day/night cycle in 3 groups of control (16 h light/8 h dark), continuous light and darkness. The results showed that acteoside and echinacoside levels in each group peaked during the night and day, respectively. Thus, the PhGs production follows a rhythmic behavior in S. striata, which is probably controlled by circadian clock. Also, the levels of photosynthetic pigments, carbohydrates, amino acids, phenolic acids, phytohormones and phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) enzyme activities varied diel in a similar or different way among study groups. The observations revealed that light/dark cycle controls the carbon and energy flow from light reception to the production and consumption of starch, biosynthesis of phenylalanine, tyrosine, cinnamic acid and coumaric acid, activation of hormonal signaling pathways and enzymes involved in phenylpropanoid pathway. Overall, it can be concluded that PhGs accumulation time-dependent patterns is likely due to daily fluctuations in upstream metabolic reactions induced by light/dark cycle.

Polyphenols Extraction From Vegetable Wastes Using a Green and Sustainable Method

Food systems have the potential to support human health, respecting the environmental sustainability principles. Food sustainability, enclosed in the concept of environmental sustainability, involves different aspects, including the recycling of food waste derived from the agri-food production chain, the use of biotechnologies ensuring the sustainability of the recovery processes of bioactive compounds from food waste and, last but not least, the awareness of having to consume and waste less food. Food loss and waste is generated during the whole supply chain, from production to household utilization. The utilization of agricultural wastes as an abundant, renewable and low-cost source for the production of high value-added products is currently explored. The bioactive compounds present in these sources have been proved to possess a wide range of biological activities; therefore, research is needed into the application of environmentally friendly traditional and advanced techniques with low production costs in the extraction, isolation and purification of phytochemical compounds from agricultural wastes in high yields and at maximal quality. Authors of this manuscript propose and discuss an innovative and sustainable extraction system of polyphenols from vegetable waste, based on an enzymatic pre-treatment coupled with a solid-liquid extraction by using a particular extractor (Naviglio Estrattore®). This extraction system, organic solvent free, allowed to extract relevant amount of polyphenols (flavonoids in particular) from several vegetable waste products.

Exogenous naringenin improved digestible protein accumulation and altered morphology via VrPIN and auxin redistribution in Vigna radiata

Naringenin exposure altered auxin redistribution via VrPIN1 leading to morphological alterations and significantly reduced the protein precipitable tannins that further enhanced the protein accumulation and bioavailability. Flavonoid exposure is known to affect the antioxidant profile of legumes. However, a detailed study evaluating the effect of flavonoid naringenin on morphology and biochemical profile of legume is lacking. The present study is a novel report of improved in planta protein bioavailability and antioxidant potential of legume mungbean on naringenin exposure. The quantitative evaluation revealed significant protein accumulation (64-122 μg/g FW) on naringenin exposure. Further, an increase in protein solubility and digestibility compared to control was evident. Naringenin mediated altered α-amylase activity improved the mungbean seed germination rate. Naringenin induced auxin redistribution and altered PIN formed transcript expression reduced lateral root density and increased stem length that was subsequently reverted on exogenous indole acetic acid application. Naringenin enhanced polyphenolic accumulation and improved the antioxidant potential of mungbean. Additionally, the responsiveness of the early gene of the flavonoid biosynthetic pathway, Chalcone isomerase to naringenin concentration was revealed indicating a probable feedback regulation. Further, the presence of alternate liquiritigenin biosynthesis was also evident. The present study, thus reveals the probable potential of phytochemical naringenin towards agricultural sustainability in the changing environmental conditions.

The time of the day to harvest affects the degreening, antioxidant compounds, and protein content during postharvest storage of broccoli

Harvesting of broccoli at several moments of the day affects the rate of senescence during storage. In this work, broccoli heads were harvested at several moments and then kept at 20°C in order to analyze protein metabolism and antioxidant compounds. Almost no differences were detected in the contents of total and soluble proteins, and free amino acids. Only an increment in free amino acids was detected by day 3 in samples obtained at 8:00 hr. With reference to antioxidants, the contents of ascorbic acid, carotenoids and xanthophylls, phenols, and flavonoids were similar in samples harvested at different moments. However, an increment was detected in carotenoids, phenols, and flavonoids during storage of samples collected at 18:00 hr on day 3 and samples collected at 13:00 hr on day 5. The combination of delay of senescence and increment in antioxidants suggest harvesting at 12:00 or 18:00 hr. PRACTICAL APPLICATION: Broccoli is a vegetable with an important level of nutrients. However, it is also highly perishable and suffers a high rate of senescence and loss of quality during postharvest. In this work, it is demonstrated that the simple practice of harvests in different moments of the day can affect the postharvest behavior of broccoli, and it is suggested to carry out the harvest toward the end of the day.

Preservative effect of Chinese cabbage (Brassica rapa subsp. pekinensis) extract on their molecular docking, antioxidant and antimicrobial properties

This study aimed at investigating the antimicrobial activity of different solvent extracts of Chinese cabbage Brassica rapa subsp. pekinensis (BRARP) and their antioxidant and cytotoxicity properties. Of the different solvents extracts, the chloroform extracts (CE) were significantly inhibited the bacterial pathogens at minimum inhibitory concentration (MIC) of 16.5 mg.mL^-1. Biochemical analysis revealed that total phenol (62.6 ± 0.05 mg GAE.g^-1) and flavonoids (27.6 ± 0.04 mg QE.g^-1) were higher in the extracts of BRARP, which resulted in enhanced antioxidant activity in CE. A total of eight dominant compounds were detected in the potent antimicrobial extract from BRARP based on GC-MS analysis. The molecular interactions study revealed that, among the screened compounds the 1,2-benzenedicarboxylic acid and 2,3-dicyanopropionamide interacted with the active site of pathogenicity and survival related protein with lipopolysaccharide (LpxC) with higer binding energy. This work concluded that the 1, 2-Benzenedicarboxylic acid and 2, 3-Dicyanopropionamide from BRARP was reported to be good non-cytotoxic and antioxidant antimicrobials against bacterial pathogens.