Effects of derivatization and probiotic transformation on the antioxidative activity of fruit polyphenols.

Fruits contain numerous polyphenols in the form of conjugates, which exhibit low antioxidant activity. Probiotic fermentation is a strategy to improve the antioxidant activity of these conjugated polyphenols by modifying their structure. However, the mechanisms underlying the effects of functional groups and derivatizations on the antioxidative activities of polyphenols and the antioxidation enhancement by probiotic biotransformation haven't been comprehensively explored. This review aimed to explore the structure-antioxidant activity relationships of four functional groups and three derivatizations in flavonoids and phenolic acids. Further, the review elucidated the antioxidant mechanisms underlying the biotransformation of flavonoids and phenolic acids as glycoside, methylated, and ester conjugates by probiotic biotransformation. Deglycosylation, demethylation, and hydrolysis catalyzed by enzymes produced by Bifidobacterium and Lactobacillus facilitated the conversion of conjugated polyphenols into flavonoids and phenolic acids with hydrolyzed forms and highly active functional groups, thereby increasing hydrogen supply and electron transfer capacity to enhance the antioxidant activity.

Identification and molecular mechanism of novel antioxidant peptide from fish sauce: A combined quantum chemistry and molecular simulation.

Fish sauce, derived from fermented fish, exhibits a notable antioxidant effect after a six-month fermentation process, and we propose that potential antioxidant peptides were present in the fish sauce. We isolated, purified, and identified potential bioactive antioxidant peptides by using fish sauce fermented for 6 months. Additionally, molecular simulation was employed to investigate the antioxidant action mechanism of these bioactive peptides. The molecular docking results revealed that FS4-1 (MHQLSKK), FS4-2 (VLDNSPER), FS4-3 (MNPPAASIK), FS6-1(VLKQAAAGR), and FS6-2 (SPDVSPRR), could dock with the Keap1 receptor. The primary force (Van der Waals' force and hydrogen bonds) and key sites (GLY509 and ALA510) of Keap1 binding to peptides were determined. The active center was located in the side chain of amino acid Met at positions C7H78 and C7H79. We here identified antioxidant peptides in fish sauce and revealed the antioxidant mechanism through molecular simulations.

Scavenging of reactive oxygen species in Candidatus Brocadia fulgida through nanocompartments.

The antioxidant defense mechanisms for anaerobic ammonia oxidation (anammox) bacteria are still unclear. In this study, the potential antioxidant ability of nanocompartments in Candidatus Brocadia fulgida to typical reactive oxygen species (ROS) was investigated. The results showed that the copies of genes involved in anammox central metabolism were inhibited with hydrogen peroxide (H2O2), while the genes encoded putative anti-oxidative protein (nanocompartments and cargo HAO) up-regulated. The genetically engineered bacteria grew better and maintained the lower ROS levels (65.60 %-78.07 %) and higher electron transport activities (∼5-21 times) than the wild bacteria under H2O2 stimulus. Molecular docking confirmed that nanocompartment proteins could provide diverse sites to bind with H2O2 based on heme as the redox center. Additionally, the nanocompartments induced up-regulation of multiple protective pathways for coping with oxidative stress from H2O2, including antioxidant enzymes and other non-enzymatic pathways. Thus, the heme-containing nanocompartments presented great potential in preventing and relieving oxidative stress.

Salicylic acid improves cowpea productivity under water restriction in the field by modulating metabolism.

Introduction: Salicylic acid has shown promise in alleviating water stress in cultivated plants. However, there is a lack of studies confirming its effectiveness in cowpea plants grown in field conditions. Therefore, this research aimed to evaluate the use of salicylic acid as a water stress mitigator in cowpea cultivars under different irrigation depths in field conditions. Methods: Four cowpea cultivars (BRS Novaera, BRS Tapaihum, BRS Pujante, and BRS Pajeú) were subjected to different treatments: control (W100: 100% replacement of crop evapotranspiration - ETc), W50 (50% of ETc), W50+SA2 (50% of ETc + 276 mg L-1 of SA), and W50+SA4 (50% of ETc + 552 mg L-1 of SA). The treatments were combined in a 4×4 factorial scheme with three replications, arranged in a randomized block design. Results: Water restriction had a negative impact on the water status, growth, gas exchange, and production of the cultivars while also leading to changes in the antioxidant metabolism and osmolyte concentration. The application of SA enhanced antioxidant activity and the synthesis of osmotic adjusters under stress conditions. The most effective concentration was 276 mg L-1 in stage R2 and 552 mg L-1 in stage V7, respectively. The BRS Pujante cultivar showed increased productivity under water restriction with SA application, while the BRS Tapaihum was the most tolerant among the cultivars studied. Discussion: In summary, our findings underscore the importance of using SA to mitigate the effects of water restriction on cowpea cultivation. These discoveries are crucial for the sustainability of cowpea production in regions susceptible to drought, which can contribute to food security. We further add that the adoption of new agricultural practices can enhance the resilience and productivity of cowpea as an essential and sustainable food source for vulnerable populations in various parts of the world.

Identification and molecular docking of novel antioxidant peptides from Candida utilis.

The current trend is the promotion of antioxidants that are beneficial for both health and the environment. Candida utilis have garnered considerable attention due to their commendable attributes such as non-toxicity and the ability to thrive in waste. Therefore, Candida utilis was used as raw material to isolate and identify new antioxidant peptides by employing methods such as ultrafiltration, DEAE Sepharose Fast Flow, and liquid chromatography-tandem mass spectrometry. The antioxidant mechanism of peptides was investigated by molecular docking. The properties of antioxidant peptides were evaluated using a variety of computational tools. This study resulted in the identification of two novel antioxidant peptides. According to the molecular docking results, the antioxidant mechanism of Candida utilis peptides operates by obstructing the entry to the myeloperoxidase activity cavity. The (-) CDOCKER energy of antioxidant peptides was 6.2 and 6.1 kcal/mol, respectively. Additionally, computer predictions indicated that antioxidant peptides exhibited non-toxicity and poor solubility.

Gamma-aminobutyric acid (GABA) improves salinity stress tolerance in soybean seedlings by modulating their mineral nutrition, osmolyte contents, and ascorbate-glutathione cycle.

BACKGROUND: In plants, GABA plays a critical role in regulating salinity stress tolerance. However, the response of soybean seedlings (Glycine max L.) to exogenous gamma-aminobutyric acid (GABA) under saline stress conditions has not been fully elucidated. RESULTS: This study investigated the effects of exogenous GABA (2 mM) on plant biomass and the physiological mechanism through which soybean plants are affected by saline stress conditions (0, 40, and 80 mM of NaCl and Na2SO4 at a 1:1 molar ratio). We noticed that increased salinity stress negatively impacted the growth and metabolism of soybean seedlings, compared to control. The root-stem-leaf biomass (27- and 33%, 20- and 58%, and 25- and 59% under 40- and 80 mM stress, respectively]) and the concentration of chlorophyll a and chlorophyll b significantly decreased. Moreover, the carotenoid content increased significantly (by 35%) following treatment with 40 mM stress. The results exhibited significant increase in the concentration of hydrogen peroxide (H2O2), malondialdehyde (MDA), dehydroascorbic acid (DHA) oxidized glutathione (GSSG), Na+, and Cl- under 40- and 80 mM stress levels, respectively. However, the concentration of mineral nutrients, soluble proteins, and soluble sugars reduced significantly under both salinity stress levels. In contrast, the proline and glycine betaine concentrations increased compared with those in the control group. Moreover, the enzymatic activities of ascorbate peroxidase, monodehydroascorbate reductase, glutathione reductase, and glutathione peroxidase decreased significantly, while those of superoxide dismutase, catalase, peroxidase, and dehydroascorbate reductase increased following saline stress, indicating the overall sensitivity of the ascorbate-glutathione cycle (AsA-GSH). However, exogenous GABA decreased Na+, Cl-, H2O2, and MDA concentration but enhanced photosynthetic pigments, mineral nutrients (K+, K+/Na+ ratio, Zn2+, Fe2+, Mg2+, and Ca2+); osmolytes (proline, glycine betaine, soluble sugar, and soluble protein); enzymatic antioxidant activities; and AsA-GSH pools, thus reducing salinity-associated stress damage and resulting in improved growth and biomass. The positive impact of exogenously applied GABA on soybean plants could be attributed to its ability to improve their physiological stress response mechanisms and reduce harmful substances. CONCLUSION: Applying GABA to soybean plants could be an effective strategy for mitigating salinity stress. In the future, molecular studies may contribute to a better understanding of the mechanisms by which GABA regulates salt tolerance in soybeans.

Naringin attenuates Actinobacillus pleuropneumoniae-induced acute lung injury via MAPK/NF-κB and Keap1/Nrf2/HO-1 pathway.

Actinobacillus pleuropneumoniae (APP) causes porcine pleuropneumonia (PCP), which is clinically characterized by acute hemorrhagic, necrotizing pneumonia, and chronic fibrinous pneumonia. Although many measures have been taken to prevent the disease, prevention and control of the disease are becoming increasingly difficult due to the abundance of APP sera, weak vaccine cross-protection, and increasing antibiotic resistance in APP. Therefore, there is an urgent need to develop novel drugs against APP infection to prevent the spread of APP. Naringin (NAR) has been reported to have an excellent therapeutic effect on pulmonary diseases, but its therapeutic effect on lung injury caused by APP is not apparent. Our research has shown that NAR was able to alleviate APP-induced weight loss and quantity of food taken and reduce the number of WBCs and NEs in peripheral blood in mice; pathological tissue sections showed that NAR was able to prevent and control APP-induced pathological lung injury effectively; based on the establishment of an in vivo/in vitro model of APP inflammation, it was found that NAR was able to play an anti-inflammatory role through inhibiting the MAPK/NF-κB signaling pathway and exerting anti-inflammatory effects; additionally, NAR activating the Nrf2 signalling pathway, increasing the secretion of antioxidant enzymes Nqo1, CAT, and SOD1, inhibiting the secretion of oxidative damage factors NOS2 and COX2, and enhancing the antioxidant stress ability, thus playing an antioxidant role. In summary, NAR can relieve severe lung injury caused by APP by reducing excessive inflammatory response and improving antioxidant capacity.

Advances in Research on the Activity Evaluation, Mechanism and Structure-Activity Relationships of Natural Antioxidant Peptides.

Antioxidant peptides are a class of biologically active peptides with low molecular weights and stable antioxidant properties that are isolated from proteins. In this review, the progress in research on the activity evaluation, action mechanism, and structure-activity relationships of natural antioxidant peptides are summarized. The methods used to evaluate antioxidant activity are mainly classified into three categories: in vitro chemical, in vitro cellular, and in vivo animal methods. Also, the biological effects produced by these three methods are listed: the scavenging of free radicals, chelation of metal ions, inhibition of lipid peroxidation, inhibition of oxidative enzyme activities, and activation of antioxidant enzymes and non-enzymatic systems. The antioxidant effects of natural peptides primarily consist of the regulation of redox signaling pathways, which includes activation of the Nrf2 pathway and the inhibition of the NF-κB pathway. The structure-activity relationships of the antioxidant peptides are investigated, including the effects of peptide molecular weight, amino acid composition and sequence, and secondary structure on antioxidant activity. In addition, four computer-assisted methods (molecular docking, molecular dynamics simulation, quantum chemical calculations, and the determination of quantitative structure-activity relationships) for analyzing the structure-activity effects of natural peptides are summarized. Thus, this review lays a theoretical foundation for the development of new antioxidants, nutraceuticals, and cosmetics.

A Kinetic Approach to Oxygen Radical Absorbance Capacity (ORAC): Restoring Order to the Antioxidant Activity of Hydroxycinnamic Acids and Fruit Juices.

This study introduces a kinetic model that significantly improves the interpretation of the oxygen radical absorbance capacity (ORAC) assay. Our model accurately simulates and fits the bleaching kinetics of fluorescein in the presence of various antioxidants, achieving high correlation values (R2 > 0.99) with the experimental data. The fit to the experimental data is achieved by optimizing two rate constants, k5 and k6. The k5 value reflects the reactivity of antioxidants toward scavenging peroxyl radicals, whereas k6 measures the ability of antioxidants to regenerate oxidized fluorescein. These parameters (1) allow the detailed classification of cinnamic acids based on their structure-activity relationships, (2) provide insights into the interaction of alkoxyl radicals with fluorescein, and (3) account for the regeneration of fluorescein radicals by antioxidants. The application of the model to different antioxidants and fruit extracts reveals significant deviations from the results of traditional ORAC tests based on the area under the curve (AUC) approach. For example, lemon juice, rich in 'fast' antioxidants such as ascorbic acid, shows a high k5 value, in contrast to its low AUC values. This finding underscores the limitations of the AUC approach and highlights the advantages of our kinetic model in understanding antioxidative dynamics in food systems. This study presents a comprehensive, quantitative, mechanism-oriented approach to assessing antioxidant reactivity, demonstrating a significant improvement in ORAC assay applications.

Research Progress on the Antioxidant Activity of Natural Diarylheptanoids: Mechanisms and Structure-activity Relationships.

Antioxidant research has recently become a popular topic. Medicinal plants are important sources of novel active compounds. Diarylheptanoids, a typical family of secondary plant metabolites, are of great interest owing to their extensive spectrum of biological activities. They possess a unique 1,7-diphenylmethane structural skeleton. Thus, this review summarizes the natural linear or macrocyclic diarylheptanoids with antioxidant activity in the last two decades. In addition, the relationships between the structural characteristics of natural diarylheptanoids and their antioxidant capacity were also discussed. All the available data highlight the potential of natural diarylheptanoids as novel antioxidants.

Survey on Antioxidants Used as Additives to Improve Biodiesel's Stability to Degradation through Oxidation.

A major problem that limits the use of biodiesel is maintaining the fuel at the specified standards for a longer period. Biodiesel oxidizes much more easily than diesel, and the final oxidation products change its physical and chemical properties and cause the formation of insoluble gums that can block fuel filters and the supply pipes. This instability of biodiesel is a major problem and has not yet been satisfactorily resolved. Recently, the use of biodiesel has increased quite a lot, but the problem related to oxidation could become a significant impediment. A promising and cost-effective approach to improving biodiesel's stability is to add appropriate antioxidants. Antioxidants work better or less effectively in different biodiesel fuels, and there is no one-size-fits-all inhibitor for every type of biodiesel fuel. To establish a suitable antioxidant for a certain type of biodiesel, it is necessary to know the chemistry of the antioxidants and factors that influence their effectiveness against biodiesel oxidation. Most studies on the use of antioxidants to improve the oxidative stability of biodiesel have been conducted independently. This study presents an analysis of these studies and mentions factors that must be taken into account for the choice of antioxidants so that the storage stability of biodiesel fuels can be improved.

A Review on Bioactive Anthraquinone and Derivatives as the Regulators for ROS.

Anthraquinones are bioactive natural products, which are often found in medicinal herbs. These compounds exert antioxidant-related pharmacological actions including neuroprotective effects, anti-inflammation, anticancer, hepatoprotective effects and anti-aging, etc. Considering the benefits from their pharmacological use, recently, there was an upsurge in the development and utilization of anthraquinones as reactive oxygen species (ROS) regulators. In this review, a deep discussion was carried out on their antioxidant activities and the structure-activity relationships. The antioxidant mechanisms and the chemistry behind the antioxidant activities of both natural and synthesized compounds were furtherly explored and demonstrated. Due to the specific chemical activity of ROS, antioxidants are essential for human health. Therefore, the development of reagents that regulate the imbalance between ROS formation and elimination should be more extensive and rational, and the exploration of antioxidant mechanisms of anthraquinones may provide new therapeutic tools and ideas for various diseases mediated by ROS.

The Multifaceted Effects of Short-Term Acute Hypoxia Stress: Insights into the Tolerance Mechanism of Propsilocerus akamusi (Diptera: Chironomidae).

Plenty of freshwater species, especially macroinvertebrates that are essential to the provision of numerous ecosystem functions, encounter higher mortality due to acute hypoxia. However, within the family Chironomidae, a wide range of tolerance to hypoxia/anoxia is displayed. Propsilocerus akamusi depends on this great tolerance to become a dominant species in eutrophic lakes. To further understand how P. akamusi responds to acute hypoxic stress, we used multi-omics analysis in combination with histomorphological characteristics and physiological indicators. Thus, we set up two groups-a control group (DO 8.4 mg/L) and a hypoxic group (DO 0.39 mg/L)-to evaluate enzyme activity and the transcriptome, metabolome, and histomorphological characteristics. With blue-black chromatin, cell tightness, cell membrane invagination, and the production of apoptotic vesicles, tissue cells displayed typical apoptotic features in the hypoxic group. Although lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), catalase (CAT), and Na+/K+ -ATPase (NKA) activities were dramatically enhanced under hypoxic stress, glycogen content, and superoxide dismutase (SOD) activities were significantly reduced compared to the control group. The combined analysis of the transcriptome and metabolome, which further demonstrated, in addition to carbohydrates, including glycogen, the involvement of energy metabolism pathways, including fatty acid, protein, trehalose, and glyoxylate cycles, provided additional support for the aforementioned findings. Lactate is the end product of glycogen degradation, and HIF-1 plays an important role in promoting glycogenolysis in acute hypoxic conditions. However, we discovered that the ethanol tested under hypoxic stress likely originates from the symbiodinium of P. akamusi. These results imply that some parameters related to energy metabolism, antioxidant enzyme activities, and histomorphological features may be used as biomarkers of eutrophic lakes in Chironomus riparius larvae. The study also provides a scientific reference for assessing toxicity and favoring policies to reduce their impact on the environment.

Liver proteomics analysis reveals the differentiation of lipid mechanism and antioxidant enzyme activity during chicken embryonic development.

Chicken embryo development is a dynamic process. However, no detailed information is available about the protein abundance changes associated with the lipid mechanism and antioxidant enzyme activity during the egg embryo development. Thus, in the present study, an TMT-based proteomic approach was used to quantify protein abundance changes at different stages of chicken embryonic development. A total of 289 significantly differentially abundant hepatic proteins were quantified, of which 180 were upregulated and 109 were downregulated in the comparison of Day 20 with Day 12 in chicken embryos. Pathway analysis showed that metabolic pathways were the most highly enriched pathways, followed by arachidonic acid metabolism and steroid biosynthesis. Integration of proteomic-based studies profiling of three incubation stages revealed that the two compare groups (Day 12 vs Day 20 and Day 16 vs Day 20) shared some key differentially abundant proteins (DAPs), including LBFABP, FABP5, CYP4V2, PDCD4, LAL, APOA1, APOA4, SAA, FABP2, ACBSG2, FABP2, CYP51A1, and FBXO9. The STRING database and GO analysis results showed that there was close connectivity between APOA4, LBFABP, SERPINC1, APOA1, FGB, FGA, ANGPTL3 and these proteins were involved in the oxidation-reduction process, lipid transport, iron ion, heme, and lipid binding. Importantly, APOA4, FABP2, and CYP51A1 might be key factors to control fat deposition and antioxidant enzyme activity during chicken embryonic development. These findings will facilitate a better understanding of antioxidant and lipid mechanisms in chicken embryo and these DAPs can be further investigated as candidate markers to predict lipid deposition and the activity of antioxidant enzymes.

Utilizing hydrothermal time models to assess the effects of temperature and osmotic stress on maize (Zea mays L.) germination and physiological responses.

The application of germination models in economic crop management makes them extremely useful for predicting seed germination. Hence, we examined the effect of varying water potentials (Ψs; 0. - 0.3, - 0.6, - 0.9, - 1.2 MPa) and temperatures (Ts; 20, 25, 30, 35, 40 °C) on maize germination and enzymatic antioxidant mechanism. We observed that varying Ts and Ψs significantly influenced germination percentage (GP) and germination rate (GR), and other germination parameters, including germination rate index (GRI), germination index (GI), mean germination index (MGI), mean germination time (MGT), coefficient of the velocity of germination (CVG), and germination energy (GE) (p ≤ 0.01). Maximum (87.60) and minimum (55.20) hydro-time constant (θH) were reported at 35 °C and 20 °C, respectively. In addition, base water potential at 50 percentiles was highest at 30 °C (15.84 MPa) and lowest at 20 °C (15.46 MPa). Furthermore, the optimal, low, and ceiling T (To, Tb and Tc, respectively) were determined as 30 °C, 20 °C and 40 °C, respectively. The highest θT1 and θT2 were reported at 40 °C (0 MPa) and 20 °C (- 0.9 MPa), respectively. HTT has a higher value (R2 = 0.43 at 40 °C) at sub-optimal than supra-optimal temperatures (R2 = 0.41 at 40 °C). Antioxidant enzymes, including peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione peroxidase (GPX), increased with decreasing Ψs. In contrast, CAT and POD were higher at 20 °C and 40 °C but declined at 25, 30, and 35 °C. The APX and GPX remained unchanged at 20, 25, 30, and 40 °C but declined at 35 °C. Thus, maintaining enzymatic activity is a protective mechanism against oxidative stress. A decline in germination characteristics may result from energy diverting to anti-stress tools (antioxidant enzymes) necessary for eliminating reactive oxygen species (ROS) to reduce salinity-induced oxidative damage. The parameters examined in this study are easily applicable to simulation models of Z. mays L. germination under extreme environmental conditions characterized by water deficits and temperature fluctuations.

[Ferroptosis:Mechanism and Role in Malignant Tumors].

Ferroptosis is a new type of programmed cell death different from other cell death pathways such as apoptosis,autophagy,necrosis,and pyroptosis in terms of initiation,mechanisms,and molecular characteristics.As the accumulation of phospholipid hydroperoxides is the hallmark of ferroptosis,the balance between oxidative damage and antioxidant defense is critical to the regulatory mechanism of ferroptosis.In cancer,the upregulation of antioxidant defense pathways can inhibit ferroptosis,thereby promoting cancer cells to survive the oxidative stress and develop drug resistance.This review systematically introduces the main features and regulatory mechanisms of ferroptosis.In addition,we summarize the role of ferroptosis in the progression and drug resistance of malignant tumors,providing novel implications for further research on the pathogenesis of malignant tumors and discovery of new targets for anti-cancer therapy.

Jasmonic acid boosts the salt tolerance of kidney beans (Phaseolus vulgaris L.) by upregulating its osmolytes and antioxidant mechanism.

As a lipid-derived compound, jasmonic acid (JA) regulates growth and defense against environmental stresses. An exogenous foliar JA application was investigated in our study (HA; 0.5 mM) on kidney bean plants (Phaseolus vulgaris L.) grown under different salinity stress concentrations (0, 75, and 150 mM NaCl). According to the results, salt concentrations were related to an increase in malondialdehyde (MDA) levels, whereas they declined the chlorophyll content index. In contrast, JA application decreased the level of MDA but increased the chlorophyll content index. Moreover, increasing salinity levels increased proline, phenolic compounds, flavonoids, free amino acid concentrations, and shikimic acid concentrations, as well as the activities of polyphenol oxidase (PPO), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD). In addition, JA applications further increased their concentrations with increasing salinity stress levels. JA application increases salt-induced osmolytes and non-enzymatic antioxidants while increasing enzymatic antioxidant activity, suggesting kidney beans have a strong antioxidant mechanism, which can adapt to salinity stress. Our results showed that exogenous JA foliar applications could enhance the salt tolerance ability of kidney bean plants by upregulating their antioxidant mechanism and osmolytes.

Radical Scavenging Capability and Mechanism of Three Isoflavonoids Extracted from Radix Astragali: A Theoretical Study.

As a valuable traditional Chinese herbal medicine, Radix Astragali has attracted much attention due to its extensive pharmacological activities. In this study, density functional theory (DFT) was used thermodynamically and kinetically in detail to predict the antioxidant activity and reaction mechanisms involved in the free radical scavenging reactions of three representative isoflavonoids (formononetin, calycosin, and calycosin-7-glucoside) extracted from Radix Astragali. Three main mechanisms, including hydrogen atom transfer (HAT), proton transfer after electron transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were examined by calculating the thermodynamic parameters. It was found that HAT is the predominant mechanism in the gas phase, while SPLET is supported in the solvent environment. The isoflavonoids' order of antioxidant activity was estimated as: calycosin > calycosin-7-glucoside > formononetin. For the calycosin compound, the result revealed the feasibility of double HAT mechanisms, which involve the formation of stable benzodioxazole with significantly reduced energy in the second H+/e- reaction. In addition, the potential energy profiles and kinetic calculations show that the reaction of •OH into the 3'-OH site of calycosin has a lower energy barrier (7.2 kcal/mol) and higher rate constant (4.55 × 109 M-1 s-1) compared with other reactions in the gas phase.

Mechanistic insight into the free radical scavenging and xanthine oxidase (XO) inhibitor potent of monoacetylphloroglucinols (MAPGs).

Three novel antioxidant candidates based on phenolic polyketide, monoacetylphloroglucinol (MAPG), a natural antibiotic compound produced by plant growth-promoting rhizobacteria (PGPR), Pseudomonas fluorescens F113 have been proposed. Initially, a green and highly efficient route to the synthesis of MAPG and its two analogues from phloroglucinol (PG) has been developed. Afterward, their rational mechanism of antioxidant activity has been investigated based on thermodynamic descriptors involved in the double (2H+/2e-) radical trapping processes. These calculations have been performed using the systematic density functional theory (DFT) method at the B3LYP/Def2-SVP level of theory in the gas phase and aqueous solution. Our findings reveal that the double formal hydrogen atom transfer (df-HAT) mechanism is preferred in the gas phase, while the double sequential proton loss electron transfer (dSPLET) mechanism is preferred in aqueous solution for all MAPGs. The 6-OH group represents the most favorable site for trapping radical species for all MAPGs, which is supported by the pKa values obtained from DFT calculations. The role of acyl substituents on the PG ring has been comprehensively discussed. The presence of acyl substituents has a strong influence on the thermodynamic parameters of the phenolic O-H bond in PG. These results are supported by frontier molecular orbitals (FMOs) analysis, where the addition of acyl substituents increases the chemical reactivity of MAPGs significantly. Based on molecular docking and molecular dynamic simulations (MDs), MAPGs are also predicted to be promising candidates for xanthine oxidase (XO) inhibition.HighlightsThe antioxidant activity of the three synthesized monoacetylphloroglucinols (MAPGs) has been investigated using the density functional theory (DFT) method.Acyl substituents increase the chemical reactivity and antioxidant activity of MAPGs.Double formal hydrogen atom transfer (df-HAT) is the preferred mechanism in the gas phase.Double sequential proton loss electron transfer (dSPLET) seems to be more favored in aqueous solution.MAPGs are expected to be promising xanthine oxidase (XO) inhibitors.

Drought-triggered leaf transcriptional responses disclose key molecular pathways underlying leaf water use efficiency in sugarcane (Saccharum spp.).

Drought is a major constraint to sugarcane (Saccharum spp.) production and improving the water use efficiency (WUE) is a critical trait for the sustainability of this bioenergy crop. The molecular mechanism underlying WUE remains underexplored in sugarcane. Here, we investigated the drought-triggered physiological and transcriptional responses of two sugarcane cultivars contrasting for drought tolerance, 'IACSP97-7065' (sensitive) and 'IACSP94-2094' (tolerant). After 21 days without irrigation (DWI), only 'IACSP94-2094' exhibited superior WUE and instantaneous carboxylation efficiency, with the net CO2 assimilation being less impacted when compared with 'IACSP97-7065'. RNA-seq of sugarcane leaves at 21 DWI revealed a total of 1,585 differentially expressed genes (DEGs) for both genotypes, among which 'IACSP94-2094' showed 617 (38.9%) exclusive transcripts (212 up- and 405 down-regulated). Functional enrichment analyses of these unique DEGs revealed several relevant biological processes, such as photosynthesis, transcription factors, signal transduction, solute transport, and redox homeostasis. The better drought-responsiveness of 'IACSP94-2094' suggested signaling cascades that foster transcriptional regulation of genes implicated in the Calvin cycle and transport of water and carbon dioxide, which are expected to support the high WUE and carboxylation efficiency observed for this genotype under water deficit. Moreover, the robust antioxidant system of the drought-tolerant genotype might serve as a molecular shield against the drought-associated overproduction of reactive oxygen species. This study provides relevant data that may be used to develop novel strategies for sugarcane breeding programs and to understand the genetic basis of drought tolerance and WUE improvement of sugarcane.