Physicochemical and Biochemical Characterization, Total Phenolic and Energy Value from Bulbs of Different Onion (Allium cepa L.) Varieties in Senegal

The purpose of this study is to investigate the physicochemical properties of some local varieties of onion (Allium cepa L.) and compare them with an imported variety, all collected in May 2021. Proteins, reducing sugars, lipids, and polyphenol content were estimated according to the AFNOR standardized methods. The determination of calcium, magnesium, iron, sodium, potassium and phosphorus was performed by atomic absorption spectrophotometer coupled with a CCD detector. The results highlighted an average acidity of 0.377% ± 0.002% lower than the value of the imported variety which is 0.520% ± 0.001%. Local varieties have a pH ranging from 6.35 ± 0.003 to 6.42 ± 0.004, while the variety has a pH of 6.36 ± 0.003. The ash and dry matter contents vary respectively from 4.788% ± 0.004% to 8.253% ± 0.003% and 7.945% ± 0.021% to 11.945% ± 0.007% for the local varieties. Moreover, the imported one has ash and dry matter contents of 5.175% ± 0.007% and 10.035% ± 0.021% respectively. The results show that the protein, reducing sugar and lipid contents in the local onion varieties vary respectively from 2.815 ± 0.000 to 15.634 ± 0.001 g·100 g-1;4.691 ± 0.001 to 12.596 ± 0.002 g·100 g-1 and 0.006 ± 0.001 to 0.050 ± 0.057 g·100 g-1. Furthermore, the imported variety has a protein, reducing sugar and lipid content of 5.649 ± 0.002;8.565 ± 0.002 g·100 g-1 and 0.011 ± 0.010 g·100 g-1 respectively. The maximum levels of total polyphenols are obtained in the imported variety, Bellani and Gandiol, respectively 9.973 ± 0.001, 4.535 ± 0.002, and 3.425 ± 0.006 mg EAG/g of dry matter. The local varieties have a significant calorific intake of between 35.451 ± 0.001 and 112.980 ± 0.003 kcal·100 g-1 compared to the imported one with an energy value of 56.953 ± 0.001 kcal·100 g-1 of dry matter. The bulbs of different onion varieties studied have a fairly high content of mineral elements. The potassium content of local varieties is between 502.16 ± 0.06 mg·100 g-1 and 582.77 ± 0.04 mg·100 g-1 while the imported variety has a content of 536.62 ± 1.30 mg·100 g-1. They note that the local varieties have a better calcium content (249.75 ± 0.07 to 434.20 ± 0.57 mg·100 g-1) and magnesium (142.15 ± 0.07 to 162.60 ± 0.42 mg·100 g-1) than the imported variety (229.58 ± 0.04 mg·100 g-1) except for the varieties White Grano (228.29 ± 0.01 mg·100 g-1) and Rouge Amposta (117.00 ± 0.42 mg·100 g-1) respectively. These results reveal that Gandiol, Dayo and Orient F1 are nutritionally found better due to their higher antioxidant property, proteins, carbohydrates, and reducing sugar and should be included in diets to supplement our daily allowance needed by the body.

Tandem hydroalkylation and deoxygenation of lignin-derived phenolics to synthesize high-density fuels

Lignin is the most abundant naturally phenolic biomass,and the synthesis of high-performance renewable fuel from lignin has attracted significant attention.We propose the efficient synthesis of high-density fuels using simulated lignin cracked oil in tandem with hydroalkylation and deoxygenation reactions.First,we investigated the reaction pathway for the hydroalkylation of phenol,which competes with the hydrodeoxygenation form cyclohexane.And then,we investigated the effects of metal catalyst types,the loading amount of metallic,acid dosage,and reactant ratio on the reaction results.The phenol hydroalkylation and hydrodeoxygenation were balanced when 180℃ and 5 MPa H_(2)with the alkanes yield of 95%.By extending the substrate to other lignin-derived phenolics and simulated lignin cracked oil,we obtained the polycyclic alkane fuel with high density of 0.918 g·ml^(-1)and calorific value of41.2 MJ·L^(-1).Besides,the fuel has good low-temperature properties(viscosity of 9.3 mm^(2)·s^(-1)at 20℃ and freezing point below-55℃),which is expected to be used as jet fuel.This work provides a promising way for the easy and green production of high-density fuel directly from real lignin oil.

Nano-silica modified lightweight and high-toughness carbon fiber/phenolic ablator with excellent thermal insulation and ablation performance

Lightweight and high-toughness carbon fiber/phenolic ablator(CFPA)is required as the Thermal Protection System(TPS)material of aerospace vehicles for next-generation space missions.To improve the ablative properties,silica sol with good particle size distribution prepared using tetramethoxysilane(TMOS)was blended with natural rubber latex and deposited onto carbon fiber felt,which was then integrated with phenolic aerogel matrix,introducing nano-silica into the framework of CFPA.The modified CFPA with a low density of 0.28—0.31 g/cm3exhibits strain-in-fracture as high as 31.2%and thermal conductivity as low as 0.054 W/(m·K).Furthermore,a trace amount of nano-silica could effectively protect CFPA from erosion of oxidizing atmosphere in different high-temperature environments.The oxyacetylene ablation test of 3000°C for 20 s shows a mass ablation rate of 0.0225 g/s,a linear ablation rate of 0.209 mm/s for the modified CFPA,which are 9.64%and 24.82%lower than the unmodified one.Besides,the long-time butane ablation test of 1200°C for 200 s shows an insignificant recession with mass and linear ablation rate of 0.079 g/s and 0.039 mm/s,16.84%and 13.33%lower than the unmodified one.Meanwhile,the fixed thermocouple in the test also demonstrates a good thermal insulation performance with a low peak back-face temperature of 207.7°C,12.25%lower than the unmodified one.Therefore,the nano-silica modified CFPA with excellent overall performance presents promising prospects in high-temperature aerospace applications.

Quantification of Total Phenols, Total Flavonoids, Total Anthocyanins and Evaluation of Antioxidant and Antiradical Activities of Detarium Senegalense Extracts from Chad

The aim of the present work is to assess the value of Detarium Senegalense by determining the content of total phenols, total flavonoids and total anthocyanins, and by evaluating the free radical scavenging activity of Detarium Senegalense extracts. For this purpose, sequential extraction using solvents of increasing polarity was essential. The various extracts obtained underwent phytochemical and biochemical analyses. Phytochemical screening revealed the presence of flavonoids, alkaloids, tannins, polyphenols, anthocyanins and steroids/terpenes. Quantitative analysis of total polyphenols, total flavonoids and total anthocyanins yielded the following results: total flavonoids (0.803 ± 0029 mg EQ/100g P for acetone extract of roots and 0.871 ± 0.401 mg EQ/100g P for methanol extract of leaves);total polyphenols (23.298 ± 12.68 mg EAG/100g P for acetone extract of roots and 24.69 ± 0.49 401 mg EAG/100g P for methanol extract of leaves);total monomeric anthocyanins (44.697 ± 0.939 mg EC3G/100g P and 16.699 ± 0.193 mg EC3G/100g P respectively for acetone and methanol extracts of stem bark). DPPH free radical scavenging activity was 1.674 ± 0.023 mg/mL for the acetone extract and 0.934 ± 0.24 mg/mL for the methanol extract of roots. .

Distribution of antioxidants and phenolic compounds in flour milling fractions from hard red winter wheat

Mature wheat kernels contain three main parts:endosperm,bran,and germ.Flour milling results in multiple streams that are chemically different;however,the distribution of antioxidants and phenolic compounds has not been well documented in terms of conventional milling by-product streams.In this study,multiple analytical methods were used to investigate antioxidant activity and phenolic compound compositions of hard red winter wheat(whole ground wheat),the parts of a wheat kernel(bran,flour,germ),and wheat by-product streams(mill feed,red dog,shorts)for the first time.For each mill stream,phenolic compounds(total,flavonoid,and anthocyanin contents)were determined and antioxidant activities were evaluated with 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical-scavenging activity,ferric reducing/antioxidant power(FRAP),and total antioxidant capacity assays.Significant differences(P<0.05)were observed in phenolic concentrations among fractions of bran,flour,and germ milled from the same kernels and noted that germ accounts for the majority of antioxidant properties,whereas bran contains a substantial portion of phenolic compounds and anthocyanins.Mill feed was high in phenolic content(5.29 mg FAE/g),total antioxidant capacity(866 mg/g),and antioxidant activity(up to 75% DPPH inhibition and 20.26μmol FeSO_(4)/g).The comprehensive information on distribution of antioxidants and phenolic compounds provides insights for future human consumption of commonly produced co-products from flour milling,and for selecting and using different milling fractions to make foods with improved nutritional properties.

Hollow ZIF-67-derived Co@N-doped carbon nanotubes boosting the hydrogenation of phenolic compounds to alcohols

The selective hydrogenation of highly toxic phenolic compounds to generate alcohols with thermal stability,environmental friendliness,and non-toxicity is of great importance.Herein,a series of Co-based catalysts,named Co@NCNTs,were designed and constructed by direct pyrolysis of hollow ZIF-67(HZIF-67)under H_(2)/Ar atmosphere.The evolution of the catalyst surface from the shell layer assembled by ZIF-67-derived particles to the in situ-grown hollow nitrogen-doped carbon nanotubes(NCNTs)with certain length and density is achieved by adjusting the pyrolysis atmosphere and temperature.Due to the synergistic effects of in situ-formed hollow NCNTs,well-dispersed Co nanoparticles,and intact carbon matrix,the as-prepared Co@NCNTs-0.10-450 catalyst exhibits superior catalytic performance in the hydrogenation of phenolic compounds to alcohols.The turnover frequency value of Co@NCNTs-0.10-450is 3.52 h^(-1),5.9 times higher than that of Co@NCNTs-0.40-450 and 4.5 times higher than that of Co@NCNTs-0.10-550,exceeding most previously reported non-noble metal catalysts.Our findings provide new insights into the development of non-precious metal,efficient,and cost-effective metal-organic framework-derived catalysts for the hydrogenation of phenolic compounds to alcohols.

Screening for Antioxidant Phenolic Compounds from Polygonum capitatum

[Objectives]To discover antioxidant natural products from the famous Hmong medicinal plant Polygonum capitatum.[Methods]The antioxidant activities of the isolated components were evaluated by ABTS and DPPH assays.[Results]A total of 27 free phenolics were isolated form P.capitatum.Then the in vitro antioxidant potential of these components was evaluated according to the DPPH and ABTS radical scavenging assays.Among them,five compounds(13,14,17,23,and 25)showed most significant ABTS radical-scavenging activity(IC 50 values of 3.81-15.09μg/mL).And 12 components(1,2,6,7,9,12,13,14,16,17,23,and 25)showed notable radical scavenging activity against DPPH(inhibition rates>88%).[Conclusions]Most of the above bioactive compounds were reported for the first time.

Qualitative and quantitative analysis of characteristic free and bound phenolics in three colored quinoas

Quinoa is a good source of phenolics,which both exist as free and bound forms.In order to mark clear the characteristic free and bound phenolics in different quinoa samples,in this study,characteristic free and bound phenolics in three colored quinoas including WQ(white quinoa),RQ(red quinoa)and BQ(black quinoa)were investigated.Result showed a total of 14 phenolics both acted as free and bound form were analyzed in three colored quinoas(WQ,RQ and BQ).Gallic acid,vanillic acid,epicatechin,p-coumaric acid and quercetin existed both as free and bound forms were common phenolics in quinoas.The highest total free phenolics(238.10 mg/kg)and bound phenolics(3377.75 mg/kg)were presented in WQ and RQ,respectively.It indicated WQ and RQ were respectively good source of free and bound phenolics.Moreover,characteristic free and bound phenolics in three colored quinoas could be well analyzed by principal component analysis(PCA),indicating it was an effective and reliable method in distinguishing three colored quinoas based on their characteristic free and bound phenolics,respectively.

Mechanism of action of Balanophora involucrata polyphenolic compounds in the treatment of myocardial injury based on network pharmacology and molecular docking techniques

The objective of this work was to investigate the mechanism of action of Balanophora involucrata polyphenolic compounds in the treatment of myocardial injury.In the present study,Balanophora involucrata was extracted by refluxing 75%of ethanol.The obtained extract was extracted with petroleum ether,ethyl acetate and n-butanol respectively.And the ethyl acetate layer was separated.The extract was prepared by silica gel column chromatography,sephadex LH-20 elution and thin layer chromatography.After that,the Swiss target prediction database was utilized to obtain the targets of Balanophora involucrata,and the Genecards,OMIM and TTD databases were used to predict and screen the targets of Balanophora involucrata for the treatment of myocardial injury.The active ingredient-target network was constructed using Cytoscape software,and the PPI network was mapped using String database and Cytoscape software.GO bioprocess enrichment analysis and KEGG pathway enrichment analysis were performed by Metascape software to predict the mechanism of action.Molecular docking was performed in Discovery Studio 2016 client software to verify the binding of Balanophora involucrata polyphenols to key targets.In this study,six polyphenolic compounds were isolated from Balanophora involucrata.By GO enrichment analysis,1614 biological processes(BP),127 cellular compositions(CC),and 215 molecular functions(MF)were obtained;a total of 155 cross-targets were involved in the KEGG enrichment analysis.The PPI network showed that quercetin was the main active component of polyphenolic compounds against myocardial injury and that AKT1,EGFR,STAT3,SRC,ESR1,MMP9,HSP90AA1 and other related signals were associated with myocardial injury treatment.Finally,the multi-component-multi-target-multi-pathway action of Balanophora involucrata was concluded,which provided new ideas and methods for further research on the mechanism of action of Balanophora involucrata in myocardial injury.

Evaluation of Phytochemical Analysis and Total Phenol Content of Proso Millet and Barnyard Millet

Whole grains of proso and barnyard millets were sequentially extracted using different solvents(hexane,chloroform,ethyl acetate,and methanol).Phytochemical analysis was performed qualitatively,and the total phenolic content in the extracts of proso and barnyard millets was quantified.Alkaloids and cardiac glycosides were identified in all solvent extracts of both millets.Anthraquinone and glycosides yielded negative results in all solvent extracts of both millets.Among all the solvent extracts,methanol extracts of proso and barnyard millets showed the presence of major compounds such as flavonoids,terpenoids,amino acids,tannins,and phenolics compounds.The maximum amount of phenols was found in methanolic extracts of proso and barnyard millets(0.669±0.003 and 0.625±0.003),followed by the chloroform extract of proso and barnyard millets(0.284±0.002 and 0.257±0.003).The minimum amount of phenolics was found in the acetone extract of proso and barnyard millets.The methanol extract of both millets showed the presence of major compounds with high phenolic content.

The SmMYB36-SmERF6/SmERF115 module regulates the biosynthesis of tanshinones and phenolic acids in salvia miltiorrhiza hairy roots

Tanshinone and phenolic acids are the most important active substances of Salvia miltiorrhiza,and the insight into their transcriptional regulatory mechanisms is an essential process to increase their content in vivo.SmMYB36 has been found to have important regulatory functions in the synthesis of tanshinone and phenolic acid;paradoxically,its mechanism of action in S.miltiorrhiza is not clear.Here,we demonstrated that SmMYB36 functions as a promoter of tanshinones accumulation and a suppressor of phenolic acids through the generation of SmMYB36 overexpressed and chimeric SmMYB36-SRDX(EAR repressive domain)repressor hairy roots in combination with transcriptomic-metabolomic analysis.SmMYB36 directly down-regulate the key enzyme gene of primary metabolism,SmGAPC,up-regulate the tanshinones biosynthesis branch genes SmDXS2,SmGGPPS1,SmCPS1 and down-regulate the phenolic acids biosynthesis branch enzyme gene,SmRAS.Meanwhile,SmERF6,a positive regulator of tanshinone synthesis activating SmCPS1,was up-regulated and SmERF115,a positive regulator of phenolic acid biosynthesis activating SmRAS,was down-regulated.Furthermore,the seven acidic amino acids at the C-terminus of SmMYB36 are required for both self-activating domain and activation of target gene expression.As a consequence,this study contributes to reveal the potential relevance of transcription factors synergistically regulating the biosynthesis of tanshinone and phenolic acid.

The hypoglycemic potential of phenolics from functional foods and their mechanisms

Long-term postprandial hyperglycemia is a primary risk factor for developing chronic metabolic diseases such as obesity,type 2 diabetes,and cardiovascular disease.Chronic hyperglycemia induces the glycation of proteins,oxidative stress,inflammation and increases plasma insulin and lipid concentrations.Insulin resistance is the primary cause of postprandial excursions of blood glucose and lipids.Hyperglycemia can be treated by lowering dietary carbohydrates intake,digestion,and absorption.Various functional foods improve glucose metabolism by increasing insulin sensitivity and inhibitingα-glucosidase in the small intestine.Natural phytochemicals,especially active phenolics are good antioxidants and show anti-inflammatory action and regulate blood glucose.This review aimed to report on hypoglycemic properties of active phenolics from functional foods and their proposed anti-diabetic mechanisms.Nevertheless,further clinical trials are required to confirm the bioavailability,safety,and efficacy of phenolics,especially the dosage and duration of treatment,to avoid adverse effects and give better dietary recommendations.

The SmNPR4-SmTGA5 module regulates SA-mediated phenolic acid biosynthesis in Salvia miltiorrhiza hairy roots

Phenolic acids are the main bioactive compounds in Salvia miltiorrhiza,which can be increased by salicylic acid(SA)elicitation.However,the specific molecular mechanism remains unclear.The nonexpresser of PR genes 1(NPR1)and its family members are essential components of the SA signaling pathway.Here,we report an NPR protein,SmNPR4,that showed strong expression in hairy root after SA treatment,acting as a negative moderator of SA-induced phenolic acid biosynthesis in S.miltiorrhiza(S.miltiorrhiza).Moreover,a basic leucine zipper family transcription factor SmTGA5 was identified and was found to interact with SmNPR4.SmTGA5 activates the expression of phenolic acid biosynthesis gene SmTAT1 through binding to the as-1 element.Finally,a series of biochemical assays and dual gene overexpression analysis demonstrated that the SmNPR4 significantly inhibited the function of SmTGA5,and SA can alleviate the inhibitory effect of SmNPR4 on SmTGA5.Overall,our results reveal the molecular mechanism of salicylic acid regulating phenolic acid biosynthesis in S.miltiorrhiza and provide new insights for SA signaling to regulate secondary metabolic biosynthesis.

Study on Optimization of Ethanol Reflux Extraction of Phenolic Acids from Salvia miltiorrhiza

The extraction technology of phenolic acid compounds from Salvia miltiorrhiza by ethanol reflux was studied. In this experiment, salvianolic acid B standard was used to make the standard curve. Single factor experiment and orthogonal experiment were used to study the extraction of different ethanol concentrations, reflux times and material-to-liquid ratios. The OD value of salvianolic acid compounds was measured with a spectrophotometer. The extraction rate of phenolic acid compounds under different extraction conditions was calculated through a regression equation, so as to obtain the optimal conditions for the ethanol reflux extraction process of Salvia miltiorrhiza. The experimental data can provide a reference for the ethanol reflux extraction process of salvianolic acids in the industry. According to the experiment, the extraction rate of phenolic acids in Salvia miltiorrhiza was the highest when the ethanol concentration was 60%, the reflux time was 1.5 hours, and the ratio of material-to-liquid was 1:10.

An Excellent Gas Chromatographic Stationary Phase for Separation of Phenol and Cresol Isomers--Heptakis(2,6-di-O-pentyl-3-O-allyl)-β-Cyclodextrin

Heptakis(2.6-di-O-pentyl-3-O-ally)-β-cyclodextrin as an excellent gas chromatographic stationary phase separating phenol and cresol isomers is described.

Effect of pressure cooking on phenolic compounds of quinoa

Due to good nutritional properties and potential health benefits,quinoa has gained an increasing attention.The study aimed to analyze the effect of pressure cooking on the composition,antioxidant activity,antibacterial activity and bioavailability of phenolic compounds in four types of quinoa,and to evaluate the correlation between phenolics and its biological activities by correlation analysis.The results showed that different varieties of quinoa contained different phenolic components and their biological activities were different.Pressure cooking could significantly increase(P<0.05)the phenolic contents of quinoa,and decrease in vitro digestibility of protein.The antioxidant activity,antibacterial activity and bioavailability of quinoa were also enhanced which were positively related with phenolic contents.HPLC analysis indicated that at least twelve phenolic compounds were found in quinoa,and hyperoside,sinapic acid,rutin and ferulic acid occupied a majority of them.Correlation analysis suggested that hyperoside,quercetin,sinapic acid,ferulic acid and gallic acid made the key contribution to antioxidant and antibacterial activities of phenolic compounds of quinoa.The results provided valuable information for quinoa processing with phenolics as functional ingredient.

Effective anti-inflammatory phenolic compounds from dandelion:identification and mechanistic insights using UHPLC-ESI-MS/MS,fluorescence quenching and anisotropy,molecular docking and dynamics simulation

This novel study identifi es the effective anti-inflammatory phenolic compounds in dandelion and provides mechanistic insights into their interactions with receptor proteins(toll-like receptor 4,TLR4;co-receptor myeloid differentiation protein-2,MD-2)using UHPLC-ESI-MS/MS,lipopolysaccharide(LPS)-stimulated THP-1 cell line,fluorescence quenching and anisotropy,molecular docking(single ligand and multi-ligand docking)and molecular dynamics simulation.A 50%aqueous methanol extract had a greater anti-inflammatory effect and higher chicoric acid content,compared with the 100%water and 100%methanol extracts.Chicoric acid,chlorogenic acid,methylophiopogonone A,caffeic acid,gallic acid monohydrate and 4’-O-demethylbroussonin A had relatively high binding energies and contents in all extracts.Chicoric acid competed with chlorogenic acid,4’-O-demethylbroussonin A and quercetin for MD-2.Among dandelion’s phenolics,chicoric acid most effectively hindered TLR4-MD-2 complex formation,with a quenching constant of 0.62×10^(6) L/mol for MD-2 or TLR4 at 320 K,and binding energies of-6.87 and-5.97 kcal/mol,respectively,for MD-2 and TLR4.

Oxidation of benzene to phenol with N_(2)O over a hierarchical Fe/ZSM-5 catalyst

Catalytic oxidation of benzene with N_(2)O to phenol over the hierarchical and microporous Fe/ZSM-5-based catalysts in a continuous fixedbed reactor was investigated.The spent catalyst was in-situ regenerated by an oxidative treatment using N_(2)O and in total 10 reaction-regeneration cycles were performed.A 100% N_(2)O conversion,93.3% phenol selectivity,and high initial phenol formation rate of 16.49±0.06mmol_(phenol gcatalyst)^(-1)h^(-1)at time on stream(TOS) of 5 min,and a good phenol productivity of 147.06 mmol_(phenol gcatalyst)^(-1)during catalyst lifetime of 1800 min were obtained on a fresh hierarchical Fe/ZSM-5-Hi2.8 catalyst.With the reaction-regeneration cycle,N_(2)O conversion is fully recovered within TOS of 3 h,moreover,the phenol productivity was decreased ca.2.2±0.8% after each cycle,leading to a total phenol productivity of ca.0.44 ton_(pheol kg_(catalyst)^(-1)estimated for 300 cycles.Catalyst characterizations imply that the coke is rapidly deposited on catalyst surface in the initial TOS of 3 h(0.28 mgc_(gcatalyst)^(-1)min^(-1)) and gradually becomes graphitic during the TOS of 30 h with a slow formation rate of 0.06 mgc g_(catalyst)^(-1)min^(-1).Among others(e.g.,the decrease of textural property and acidity),the nearly complete coverage of the active Fe-O-Al sites by coke accounts for the main catalyst deactivation.Besides these reversible deactivation characteristics related to coking,the irreversible catalyst deactivation is also observed with the reaction-regeneration cycle.The latter is reflected by a further decreased amount of the active Fe-O-Al sites,which agglomerate on catalyst surface with the cycle,likely associated with the hard coke residue that is not completely removed by the regeneration.

Dual Role of Plant Phenolic Compounds as Antioxidants and Prooxidants

Natural phenolic compounds are secondary metabolites found in a wide range of plants including food crops. As many of them are known to be antioxidants and can prevent several chronic and degenerative diseases in humans, they are a part of a healthy diet. However, these antioxidants can act as prooxidants under high phenolic concentration, high pH, or in the presence of transition metal ions such as Cu2+ or Fe3+, producing reactive oxygen species (ROS) including hydroxyl radicals resulting in oxidative stress and cell toxicity. While this can lead to pathogenesis including the development of various types of cancers, elevated levels of ROS are beneficial to kill malignant cells and foodborne pathogens to improve food safety. Thus, the dual nature of phenolic compounds allows them to act as antioxidants and prooxidants. Similarly, depending on the level of prooxidant activity, ROS can induce either pathogenesis or serve as a potential agent to kill malignant cells and foodborne pathogens.

AcbHLH144 transcription factor negatively regulates phenolic biosynthesis to modulate pineapple internal browning

Internal browning(IB),a major physiological disorder of pineapples,usually happens in postharvest processes,but the underlying mechanism remains elusive.The bHLH transcription factors are involved in regulating various biological processes,but whether they could regulate tissue browning in fruit during storage remains unknown.Here we showed that the phenolic biosynthesis pathway was activated in pineapples showing IB following 9 days of storage.AcbHLH144 expression was the highest of the 180 transcription factors identified,downregulated in pineapple with IB,and negatively correlated with the major phenolic biosynthetic genes.AcbHLH144 was shown to be localized in the nucleus and its transient overexpression in pineapples and overexpression in Arabidopsis decreased phenolic biosynthesis.The yeast one-hybrid assay and electrophoretic mobility shift assay showed that AcbHLH144 directly bound to the Ac4CL5 promoter and the dual-luciferase reporter assay showed that it inactivated Ac4CL5 transcription.These results strongly suggest AcbHLH144 as a repressor for phenolic biosynthesis.Abscisic acid(ABA)alleviated IB,reduced phenolic accumulation,and downregulated phenolic biosynthetic genes,including Ac4CL5.Transcriptomic analysis showed that AcbHLH144 was the most upregulated of all 39 bHLHs in response to ABA.ABA enhanced AcbHLH144 expression,reduced phenolic contents,and downregulated phenolic biosynthetic genes in pineapples transiently overexpressing AcbHLH144.Moreover,ABA enhanced enzyme activity of GUS driven by the AcbHLH144 promoter.These results showed that AcbHLH144 as a repressor for phenolic biosynthesis could be activated by ABA.Collectively,the work demonstrated that AcbHLH144 negatively regulated phenolic biosynthesis via inactivating Ac4CL5 transcription to modulate pineapple IB.The findings provide novel insight into the role of AcbHLH144 in modulating pineapple IB during postharvest processes.