Metabolism Of Polyphenols Research Articles

Postharvest Treatment with Abscisic Acid Alleviates Chilling Injury in Zucchini Fruit by Regulating Phenolic Metabolism and Non-Enzymatic Antioxidant System.

Reports show that phytohormone abscisic acid (ABA) is involved in reducing zucchini postharvest chilling injury. During the storage of harvested fruit at low temperatures, chilling injury symptoms were associated with cell damage through the production of reactive oxygen species. In this work, we have studied the importance of different non-enzymatic antioxidants on tolerance to cold stress in zucchini fruit treated with ABA. The application of ABA increases the antioxidant capacity of zucchini fruit during storage through the accumulation of ascorbate, carotenoids and polyphenolic compounds. The quantification of specific phenols was performed by UPLC/MS-MS, observing that exogenous ABA mainly activated the production of flavonoids. The rise in all these non-enzymatic antioxidants due to ABA correlates with a reduction in oxidative stress in treated fruit during cold stress. The results showed that the ABA mainly induces antioxidant metabolism during the first day of exposure to low temperatures, and this response is key to avoiding the occurrence of chilling injury. This work suggests an important protective role of non-enzymatic antioxidants and polyphenolic metabolism in the prevention of chilling injury in zucchini fruit.

Fecal excretion kinetics provides further support for polyphenols targeting microbiota: An example with prebiotic-like phlorizin

The microbiota plays important roles for polyphenols exerting bioactivity, which needs support to calculate the accumulated polyphenols in the gastrointestinal tract. Taking phlorizin as an example, fecal excretion kinetics was suggested to be ingenious for achieving it. No phlorizin was excreted with feces, implying almost 100 % total availability. Combined with its 0–5 % bioavailability, more than 95 % of phlorizin quantitatively accumulated in the gastrointestinal tract. Instead, trace phloretin was excreted, and the acquired kinetic parameters were influenced by physical conditions and dietary patterns. Dosage-total-availability curves indicated different relationships among normal-diet and obese mice, resulting in critical dosages of ∼ 159 and ∼ 196 mg/kg when taking 95 % total availability by phloretin. The dietary matrix affects the intake, digestion, metabolism and absorption of polyphenols, and may alter its total availability, and fecal excretion kinetics can provide further support for polyphenol dietary supplements targeting microbiota.

Interactions between Gut Microbiota and Polyphenols: New Insights into the Treatment of Fatigue.

Fatigue seriously affects people's work efficiency and quality of life and has become a common health problem in modern societies around the world. The pathophysiology of fatigue is complex and not fully clear. To some degree, interactions between gut microbiota and host may be the cause of fatigue progression. Polyphenols such as tannin, tea polyphenols, curcumin, and soybean isoflavones relieve fatigue significantly. Studies have shown that the gut microbiota is able to convert these active compounds into more active metabolites through intestinal fermentation. However, the mechanism of anti-fatigue polyphenols is currently mainly analyzed from the perspective of antioxidant and anti-inflammatory effects, and changes in gut microbiota are rarely considered. This review focuses on gut microecology and systematically summarizes the latest theoretical and research findings on the interaction of gut microbiota, fatigue, and polyphenols. First, we outline the relationship between gut microbiota and fatigue, including changes in the gut microbiota during fatigue and how they interact with the host. Next, we describe the interactions between the gut microbiota and polyphenols in fatigue treatment (regulation of the gut microbiota by polyphenols and metabolism of polyphenols by the gut microbiota), and how the importance of potential active metabolites (such as urolithin) produced by the decomposition of polyphenols by gut microbiota is emerging. Based on the new perspective of gut microbiota, this review provides interesting insights into the mechanism of polyphenols in fatigue treatment and clarifies the potential of polyphenols as targets for anti-fatigue product development, aiming to provide a useful basis for further research and design.

Flavones interact with fiber to affect fecal bacterial communities in vitro

This study investigated the effects of the sugarcane flavones diosmin, diosmetin, luteolin, and tricin, and their interactions with sugarcane fiber on the modulation of gut microbiota using in vitro batch fermentation. The alteration of fecal fermentation bacterial profile was analyzed using 16S rRNA sequencing data, while the bioavailability of fiber was indicated by short-chain fatty acid (SCFA) production and metabolism of polyphenols was measured directly by phenolic metabolites. Application of diosmin, diosmetin, luteolin, and tricin without fiber had no significant effect on the overall microbiota profile after 24 h of fermentation. When fiber alone was added, total SCFA production increased, specifically that of propionic and valeric acids. However, when flavones were combined with fiber, synergistic effects on the modulation of relative abundances of different bacterial taxa was noted. In particular, the proportion of Prevotella spp. was significantly increased by the combinations of diosmin, luteolin, and tricin with fiber.

The neglected effects of polysaccharide transformation on sludge humification during anaerobic digestion with thermal hydrolysis pretreatment

Humus accumulation during sludge stabilization is attracting increasing attention because of its land use potential. This study investigated the effects of thermal hydrolysis pretreatment (THP) on sludge humification and the related regulatory mechanisms during anaerobic digestion (AD). The sludge subjected to AD with THP at 160 °C (AnD-160) exhibited 7.3% and 8.5% higher total extractable carbon (TEC) and humic acid carbon (HAC) concentrations than the unpretreated sludge, respectively, while the sludge subjected to AD with THP at 180 °C (AnD-180) exhibited 1.4% and 7.0% lower concentrations. Humification of AnD-160 and AnD-180 were enhanced and inhibited, respectively. THP influenced sludge humification during AD through both intracellular polyphenol synthesis and extracellular humus condensation pathways related to polysaccharide metabolism. The 160 °C-pretreated sludge exhibited higher polysaccharide availability (more soluble polysaccharides and reducing sugars) than the other samples and thus had more active intracellular polyphenol metabolism during AD. The polyphenol accumulation stimulated the synthesis of related condensation enzymes (polyphenol oxidase and quinone oxidoreductases), facilitating extracellular HA production during AD. However, THP at 180 °C resulted in the highest production of melanoidins with CO-C heterocycles through C = O and CH sites of polysaccharides (778.46 vs. 193.87 R.U. nm2-mL/g for the unpretreated sample). This heterocyclization decreased the polysaccharide availability and inhibited intracellular polyphenol synthesis, consequently inhibiting condensation enzymes supply and extracellular HA production during AD. Overall, this study highlights the crucial but neglected role of polysaccharides in sludge humification during AD: the availability of polysaccharides affected by their occurrence state and molecular structure could determine the humification, which can be regulated by THP at different temperature.

Changes of phenolics contents, antioxidant activities, and enzyme activities in pellicles of Juglans sigillata Dode during fruits development

ABSTRACT Phenolic compounds are important components that affect the taste and health-care function of walnuts. And phenolic compounds in walnut (Juglans sigillata Dode. cv. ‘Qianhe 7’) pellicles at three developmental stages were explored to identify their role. The results showed that the total phenolic content, total flavonoid content, ferric reducing antioxidant power, 2, 2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and 1, 1-diphenyl-2-picrylhydrazyl free radical scavenging activities in pellicles increased gradually during fruits development, and reached the maximum value at maturation period. Syringic acid, gallic acid, catechin, and rutin contents were highly significantly positively correlated with reducing power or highly significantly negatively correlated with IC50 of free radical scavenging activities. Gallic acid and rutin contents were highly significantly positively correlated with phenylalanine ammonia-lyase (PAL) activity. Total phenolic content, syringic acid, catechins, and rutin contents were highly significantly negatively correlated with cinnamate 4-hydroxylase (C4H) and 4-coumarate CoA ligase (4CL) activities. Ferulic acid content was highly significantly positively correlated with polyphenol oxidase (PPO) activity. Overall, PAL, C4H, 4CL and PPO were key enzymes in the metabolism of polyphenols, and they affected the antioxidant capacity of the pellicles by regulating the content of polyphenol during walnut fruit development.

Polyphenols and Small Phenolic Acids as Cellular Metabolic Regulators.

Polyphenols and representative small phenolic acids and molecules derived from larger constituents are dietary antioxidants from fruits, vegetables and largely other plant-based sources that have ability to scavenge free radicals. What is often neglected in polyphenol metabolism is bioavailability and the role of the gut microbiota (GMB), which has an essential role in health and disease and participates in co-metabolism with the host. The composition of the gut microbiota is in constant flux and is modified by multiple intrinsic and extrinsic factors, including antibiotics. Dietary or other factors are key modulators of the host gut milieu. In this review, we explore the role of polyphenols and select phenolic compounds as metabolic or intrinsic biochemistry regulators and explore this relationship in the context of the microbiota–gut–target organ axis in health and disease.

Exogenous application of glycine and nitrate on antioxidant and polyphenol metabolism in Brassica campestris spp. Chinensis

Pakchoi (Brassica campestris ssp. Chinensis) is a leafy vegetable which has been widely cultivated and consumed worldwide due to its low calorific value, a large supply of macro and micronutrients, beneficial phytochemicals and fibers. Amino acids have a vital role in plant nutrition; however, the effect of glycine and nitrate (Gly/NO3-N) on health-promoting phytochemicals, biomass, and antioxidant activities has gained a little attention. Thus, this study aimed to evaluate the impact of glycine and nitrate on health-promoting phytochemicals and yield/biomass of pakchoi. Glycine and nitrate were employed in different proportions (control, Gly/NO3-N = 3:1, Gly/NO3-N = 1:1, and Gly/NO3-N = 1:3 in the Venlo greenhouse, Shanghai Jiao Tong university, China. Results showed that compared to control, the treatment with Gly/NO3-N notably increased the secondary metabolites like polyphenols, flavonoids, glutathione (GSH), ascorbic acid (vitamin C), antioxidant potential (FRAP and DPPH value), and biomass in pakchoi plants. The contents of all antioxidants were high under the treatment of Gly/NO3-N（1:1). Interestingly, the contents of flavonoids were significantly enhanced (107.10%) by Gly/NO3-N = 1:1 than control plants. Furthermore, the content of Phe increased by 33.79%-86.32%, and also the activity of catabolic enzymes (CHI, CHS, C4H, and PAL) of the polyphenols pathway was found to be significantly enhanced while the activity of 4CL and DFR was restrained by the treatment of Gly/NO3-N, compared with control plants. In addition, the correlation analysis of polyphenols and flavonoids with Phe, PAL, C4H, CHS, and CHI showed a positive correlation, while a negative correlation was found in the case of 4CL and DFR. Taken together, the current findings suggest that the application of Gly/NO3-N enhanced polyphenols metabolism as well as increased the total polyphenolic content and antioxidant activity. Consequently, this combination of glycine and nitrate could be used to promote beneficial phytochemicals and yield/biomass of pakchoi.

Dietary EVOO Polyphenols and Gut Microbiota Interaction: Are There Any Sex/Gender Influences?

Accumulating evidence indicates that regular consumption of extra virgin olive oil (EVOO), the main source of fat in the Mediterranean diet, is associated with beneficial health effects and a reduced risk of developing chronic degenerative disorders. The beneficial effects of EVOO can be attributed to its unique composition in monounsaturated fats and phenolic compounds that provide important antioxidant, anti-inflammatory, and immune-modulating activities. On the other hand, it is well known that the gut microbiota has several important roles in normal human physiology, and its composition can be influenced by a multitude of environmental and lifestyle factors, among which dietary components play a relevant role. In the last few years, the two-way interaction between polyphenols, including those in EVOO, and the gut microbiota, i.e., the modulation of the microbiota by polyphenols and that of polyphenol metabolism and bioavailability by the microbiota, has attracted growing attention, being potentially relevant to explain the final effects of polyphenols, as well as of the microbiota profile. Furthermore, sex and gender can affect dietary habits, polyphenol intake, and nutrient metabolism. Lastly, it has been recently suggested that differences in gut microbiota composition could be involved in the unequal incidence of metabolic diseases observed between women and men, due to sex-dependent effects on shaping gut microbiota profiles according to diet. This review summarizes the most recent studies on the relationship between EVOO polyphenols and the gut microbiota, taking into account possible influences of sex and gender in modulating such an interaction.

Novel silkworm (Bombyx mori) sulfotransferase swSULT ST3 is involved in metabolism of polyphenols from mulberry leaves.

Polyphenols in plants are important for defense responses against microorganisms, insect herbivory, and control of feeding. Owing to their antioxidant, anti-cancer, and anti-inflammatory activities, their importance in human nutrition has been acknowledged. However, metabolism of polyphenols derived from mulberry leaves in silkworms (Bombyx mori) remains unclear. Sulfotransferases (SULT) are involved in the metabolism of xenobiotics and endogenous compounds. The purpose of this study is to investigate the metabolic mechanism of polyphenols mediated by B. mori SULT. Here, we identified a novel SULT in silkworms (herein, swSULT ST3). Recombinant swSULT ST3 overexpressed in Escherichia coli effectively sulfated polyphenols present in mulberry leaves. swSULT ST3 showed high specific activity toward genistein among the polyphenols. Genistein-7-sulfate was produced by the activity of swSULT ST3. Higher expression of swSULT ST3 mRNA was observed in the midgut and fat body than in the hemocytes, testis, ovary, and silk gland. Polyphenols inhibited the aldo-keto reductase detoxification of reactive aldehydes from mulberry leaves, and the most noticeable inhibition was observed with genistein. Our results suggest that swSULT ST3 plays a role in the detoxification of polyphenols, including genistein, and contributes to the effects of aldo-keto reductase in the midgut of silkworms. This study provides new insight into the functions of SULTs and the molecular mechanism responsible for host plant selection in lepidopteran insects.

Metabolism of polyphenols (by mammalian cells and host microbiota); significance in the production of physiological relevant metabolites

Metabolism of polyphenols (by mammalian cells and host microbiota); significance in the production of physiological relevant metabolites

Abscisic Acid and Chitosan Modulate Polyphenol Metabolism and Berry Qualities in the Domestic White-Colored Cultivar Savvatiano

During the last decade, several studies demonstrated the effect of biostimulants on the transcriptional and metabolic profile of grape berries, suggesting their application as a useful viticultural practice to improve grape and wine quality. Herein, we investigated the impact of two biostimulants—abscisic acid (0.04% w/v and 0.08% w/v) and chitosan (0.3% w/v and 0.6% w/v)—on the polyphenol metabolism of the Greek grapevine cultivar, Savvatiano, in order to determine the impact of biostimulants’ application in the concentration of phenolic compounds. The applications were performed at the veraison stage and the impact on yield, berry quality traits, metabolome and gene expression was examined at three phenological stages (veraison, middle veraison and harvest) during the 2019 and 2020 vintages. Results showed that anthocyanins increased during veraison after treatment with chitosan and abscisic acid. Additionally, stilbenoids were recorded in higher amount following the chitosan and abscisic acid treatments at harvest. Both of the abscisic acid and chitosan applications induced the expression of genes involved in stilbenoids and anthocyanin biosynthesis and resulted in increased accumulation, regardless of the vintage. Alterations in other phenylpropanoid gene expression profiles and phenolic compound concentrations were observed as well. Nevertheless, they were mostly restricted to the first vintage. Therefore, the application of abscisic acid and chitosan on the Greek cultivar Savvatiano showed promising results to induce stilbenoid metabolism and potentially increase grape defense and quality traits.

Chemical Compounds of Berry-Derived Polyphenols and Their Effects on Gut Microbiota, Inflammation, and Cancer.

Berry-derived polyphenols are bioactive compounds synthesized and secreted by several berry fruits. These polyphenols feature a diversity of chemical compounds, including phenolic acids and flavonoids. Here, we report the beneficial health effects of berry-derived polyphenols and their therapeutical application on gut-microbiota-related diseases, including inflammation and cancer. Pharmacokinetic investigations have confirmed the absorption, availability, and metabolism of berry-derived polyphenols. In vitro and in vivo tests, as well as clinical trials, showed that berry-derived polyphenols can positively modulate the gut microbiota, inhibiting inflammation and cancer development. Indeed, these compounds inhibit the growth of pathogenic bacteria and also promote beneficial bacteria. Moreover, berry-derived polyphenols exhibit therapeutic effects against different gut-microbiota-related disorders such as inflammation, cancer, and metabolic disorders. Moreover, these polyphenols can manage the inflammation via various mechanisms, in particular the inhibition of the transcriptional factor Nf-κB. Berry-derived polyphenols have also shown remarkable effects on different types of cancer, including colorectal, breast, esophageal, and prostate cancer. Moreover, certain metabolic disorders such as diabetes and atherosclerosis were also managed by berry-derived polyphenols through different mechanisms. These data showed that polyphenols from berries are a promising source of bioactive compounds capable of modulating the intestinal microbiota, and therefore managing cancer and associated metabolic diseases. However, further investigations should be carried out to determine the mechanisms of action of berry-derived polyphenol bioactive compounds to validate their safety and examinate their clinical uses.

Widely Targeted Metabolic Profiling Reveals Differences in Polyphenolic Metabolites during Rosa xanthina f. spontanea Fruit Development and Ripening.

Rose hips are rich in various nutrients and have long been used for food and medicinal purposes. Owing to the high phenolic content, rose hips can be used as natural antioxidants. In this study, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to conduct a widely targeted metabolomics analysis on the polyphenolic components of Rosa xanthina f. spontanea in three ripening stages: unripe, half-ripe and fully ripe fruit. A total of 531 polyphenol metabolites were detected, including 220 phenolic acids, 219 flavonoids, 50 tannins and 42 lignans and coumarins. There were 160 differential metabolites between unripe and half-ripe rose hips (61 downregulated and 99 upregulated) and 157 differential metabolites between half-ripe and fully ripe rose hips (107 downregulated and 50 upregulated). The results of our study not only greatly enrich the chemical composition database of rose hips but also provide metabolomics information on the changes in polyphenolic metabolism during fruit development for the first time, which will help select the optimal harvest time of rose hips to achieve better quality.

Pomegranate peel polyphenols interaction with intestinal flora and its metabolic transformation

1. Pomegranate peel polyphenols (PPPs) have anti-oxidation, anti-atherosclerosis, anti-obesity effect, and so on. However, few studies have been conducted on the absorption and transformation of pomegranate polyphenols in the gut and the biologically active forms that ultimately work in the body. 2. In this study, PPPs (300 mg/kg/day) were given to normal rats and relatively sterile rats by gavage respectively. The relatively sterile rats were obtained by neomycin sulfate (250 mg/kg/day) gavage to rats. The purpose of this study is to elaborate the relationship between intestinal flora and polyphenol metabolism of pomegranate peel, and to quantitatively analyze the transformation process of its metabolite urolithin in rats. 3. The results showed that decreased bacterial diversity could significantly reduce the abundance of PPPs metabolites in feces and urine in relatively sterile rats. PPPs can regulate intestinal flora structure, significantly enhance the content of Clostrida Firmicutes (P < 0.05), and effectively promote acetic acid, propionic acid, butyric acid, iso-butyric acid and valeric acid production in rat (P < 0.05 or P < 0.01 or P< 0.001). PPPs can significantly elevate the relative proportion of Ruminococcaceae (P < 0.05). Ruminococcaceae_NK4A214_group, Ruminococcaceae_UCG-014 and Ruminococcaceae_UCG-005 can promote the metabolic transformation of PPPs and make the utilization of Urolithin A more effective.

Impact of wheat aleurone on biomarkers of cardiovascular disease, gut microbiota and metabolites in adults with high body mass index: a double-blind, placebo-controlled, randomized clinical trial

PurposeAleurone is a cereal bran fraction containing a variety of beneficial nutrients including polyphenols, fibers, minerals and vitamins. Animal and human studies support the beneficial role of aleurone consumption in reducing cardiovascular disease (CVD) risk. Gut microbiota fiber fermentation, polyphenol metabolism and betaine/choline metabolism may in part contribute to the physiological effects of aleurone. As primary objective, this study evaluated whether wheat aleurone supplemented foods could modify plasma homocysteine. Secondary objectives included changes in CVD biomarkers, fecal microbiota composition and plasma/urine metabolite profiles.MethodsA parallel double-blind, placebo-controlled and randomized trial was carried out in two groups of obese/overweight subjects, matched for age, BMI and gender, consuming foods supplemented with either aleurone (27 g/day) (AL, n = 34) or cellulose (placebo treatment, PL, n = 33) for 4 weeks.ResultsNo significant changes in plasma homocysteine or other clinical markers were observed with either treatment. Dietary fiber intake increased after AL and PL, animal protein intake increased after PL treatment. We observed a significant increase in fecal Bifidobacterium spp with AL and Lactobacillus spp with both AL and PL, but overall fecal microbiota community structure changed little according to 16S rRNA metataxonomics. Metabolomics implicated microbial metabolism of aleurone polyphenols and revealed distinctive biomarkers of AL treatment, including alkylresorcinol, cinnamic, benzoic and ferulic acids, folic acid, fatty acids, benzoxazinoid and roasted aroma related metabolites. Correlation analysis highlighted bacterial genera potentially linked to urinary compounds derived from aleurone metabolism and clinical parameters.ConclusionsAleurone has potential to modulate the gut microbial metabolic output and increase fecal bifidobacterial abundance. However, in this study, aleurone did not impact on plasma homocysteine or other CVD biomarkers.Trial RegistrationThe study was registered at ClinicalTrials.gov (NCT02067026) on the 17th February 2014.

Transcriptome Profiling During Muscadine Berry Development Reveals the Dynamic of Polyphenols Metabolism.

Muscadine grapes accumulate higher amounts of bioactive phenolics compared with other grape species. To identify the molecular events associated with polyphenolic accumulation that influence antioxidant capacity, two contrasting muscadine genotypes (C5 and C6) with varied phenolic/flavonoid content and antioxidant activity were investigated via RNA-sequencing during berry development. The results showed that berry development is concomitant with transcriptome profile changes, which was more pronounced at the véraison (V) stage. Despite that the downregulation pattern of gene expression dominated the upregulation through berry development, the C5 genotype maintained higher expression levels. Comparative transcript profiling allowed the identification of 94 differentially expressed genes with potential relevance in regulating fruit secondary metabolism, including 18 transcription factors and 76 structural genes. The genes underlying the critical enzymes in the modification reactions of polyphenolics biosynthetic pathway, including hydroxylation, methylation, and glycosylation were more pronounced during the immature stages of prevéraison (PrV), V, and postvéraison (PoV) in the C5 genotype, resulting in more accumulation of biologically active phenolic/flavonoid derivatives. The results suggested that muscadine grapes, as in bunch grapes (Vitis sp.); possess a similar mechanism that organizes polyphenolics accumulation; however, the set of total flavonoids (TFs) and structural genes coordinating the pathway varies between the two species.

Effect of p-coumarate esters resistant against postharvest Botrytis cinerea infection in apple fruit

Gray mold rot caused by Botrytis cinerea is one of the most common diseases resulted in considerable postharvest losses of fruits. The antifungal activity of esterified p-coumarates on Botrytis rot in apple fruit were investigated. Results showed that the mycelial growth and spore germination of B. cinerea were effectively inhibited by the application of methyl p-coumarate (MpCA) and ethyl p-coumarate (EpCA). Treatments with MpCA and EpCA resulted in a large leakage of intercellular electrolytes, soluble proteins and sugars, and ultrastructural distortion of the pathogen during growth, suggesting that p-coumarate esters may act via destroying the plasma membrane of the pathogen. In addition, treatments with MpCA and EpCA significantly inhibited the infection on apple fruit by B. cinerea. MpCA and EpCA up-regulated expression of genes encoding a pathogenesis-related protein (PR1), phenylalanine ammonia-lyase (PAL) and peroxidase (POD), enhanced activities of PAL and POD, and stimulated the accumulation of chlorogenic acid and catechin in the fruit. MpCA and EpCA thereby activated the disease-resistance system and the metabolism of polyphenols and flavonoids against the infection by B. cinerea. Collectively, two p-coumarate esters could not only exert their directly antifungal activity, but also induce the defense mechanism of host apple fruit. Application of MpCA and EpCA would provide a promising approach for the control of postharvest diseases of fruits.

The physiological response of different tobacco varieties to chilling stress during the vigorous growing period

Tobacco is be sensitively affected by chilling injury in the vigorous growth period, which can easily lead to tobacco leaf browning during flue-curing and quality loss, however, the physiological response of tobacco in the prosperous period under low temperature stress is unclear. The physiological response parameters of two tobacco varieties to low temperature stress were determined. The main results were as follows: ① For tobacco in the vigorous growing period subjected to low-temperature stress at 4–16 °C, the tissue structure of chloroplast changed and photosynthetic pigments significantly decreased compared with each control with the increase of intensity of low-temperature stress. ② For tobacco in the vigorous growing period at 10–16 °C, antioxidant capacity of the protective enzyme system, osmotic adjustment capacity of the osmotic adjusting system and polyphenol metabolism in plants gradually increased due to induction of low temperature with the increase of intensity of low-temperature stress. ③ Under low-temperature stress at 4 °C, the protective enzyme system, osmotic adjusting system and polyphenol metabolism of the plants played an insignificant role in stress tolerance, which cannot be constantly enhanced based on low-temperature resistance at 10 °C. This study confirmed that under the temperature stress of 10–16 °C, the self-regulation ability of tobacco will be enhanced with the deepening of low temperature stress, but there is a critical temperature between 4 and 10 °C. The self-regulation ability of plants under low temperature stress will be inhibited.

Phenoloxidases in Plants-How Structural Diversity Enables Functional Specificity.

The metabolism of polyphenolic polymers is essential to the development and response to environmental changes of organisms from all kingdoms of life, but shows particular diversity in plants. In contrast to other biopolymers, whose polymerisation is catalysed by homologous gene families, polyphenolic metabolism depends on phenoloxidases, a group of heterogeneous oxidases that share little beyond the eponymous common substrate. In this review, we provide an overview of the differences and similarities between phenoloxidases in their protein structure, reaction mechanism, substrate specificity, and functional roles. Using the example of laccases (LACs), we also performed a meta-analysis of enzyme kinetics, a comprehensive phylogenetic analysis and machine-learning based protein structure modelling to link functions, evolution, and structures in this group of phenoloxidases. With these approaches, we generated a framework to explain the reported functional differences between paralogs, while also hinting at the likely diversity of yet undescribed LAC functions. Altogether, this review provides a basis to better understand the functional overlaps and specificities between and within the three major families of phenoloxidases, their evolutionary trajectories, and their importance for plant primary and secondary metabolism.