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1.
J Am Chem Soc ; 145(42): 22945-22953, 2023 10 25.
Artigo em Inglês | MEDLINE | ID: mdl-37769281

RESUMO

Darobactin is a heptapeptide antibiotic featuring an ether cross-link and a C-C cross-link, and both cross-links are installed by a radical S-adenosylmethionine (rSAM) enzyme DarE. How a single DarE enzyme affords the two chemically distinct cross-links remains largely obscure. Herein, by mapping the biosynthetic landscape for darobactin-like RiPP (daropeptide), we identified and characterized two novel daropeptides that lack the C-C cross-link present in darobactin and instead are solely composed of ether cross-links. Phylogenetic and mutagenesis analyses reveal that the daropeptide maturases possess intrinsic multifunctionality, catalyzing not only the formation of ether cross-link but also C-C cross-linking and Ser oxidation. Intriguingly, the different chemical outcomes are controlled by the exact substrate motifs. Our work not only provides a roadmap for the discovery of new daropeptide natural products but also offers insights into the regulatory mechanisms that govern these remarkably versatile ether cross-link-forming rSAM enzymes.


Assuntos
Éter , S-Adenosilmetionina , S-Adenosilmetionina/química , Filogenia , Éteres , Etil-Éteres , Catálise
2.
J Appl Microbiol ; 134(3)2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-36746436

RESUMO

AIMS: This study aimed to investigate the mechanism of linalool against Pseudomonas lundensis and its application on beef. METHODS AND RESULTS: Field emission scanning electron microscopy found that linalool exerted antibacterial activity with a minimum inhibitory concentration (MIC) of 1.5 ml l-1 by disrupting cell structure. Loss of cell membrane integrity was monitored due to leakage of nucleic acids and K+. In addition, respiratory depression appeared in Ps. lundensis based on inhibition of enzyme activities including hexokinase (HK), glucose 6-phosphate dehydrogenase (G6PDH), phosphofructokinase (PFK), pyruvate kinase (PK), pyruvate dehydrogenase (PDH), citrate synthase (CS), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH). Subsequently, energy limitation also occurred according to the decrease in ATP content and ATPase activity. Molecular docking confirmed that linalool can combine with enzymes in cell wall (ddlB) and energy synthesis (AtpD) pathways to exert antibacterial effect. Of note, linalool has advantages for beef preservation by delaying quality changes including pH, total volatile basic nitrogen (TVB-N) and total viable count (TVC). CONCLUSIONS: Linalool has significant inhibitory effect on Ps. lundensis, and respiratory depression driven by membrane damage is the main inhibitory mechanism.


Assuntos
Antibacterianos , Insuficiência Respiratória , Animais , Bovinos , Simulação de Acoplamento Molecular , Antibacterianos/farmacologia
3.
J Nat Prod ; 86(5): 1251-1260, 2023 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-37196240

RESUMO

Seven [4 + 2]-type triterpene-diterpene hybrids derived from a rearranged or a normal lanostane unit (dienophile) and an abietane moiety (diene), forrestiacids E-K (1-7, respectively), were further isolated and characterized from Pseudotsuga forrestii (a vulnerable conifer endemic to China). The intriguing molecules were revealed with the guidance of an LC-MS/MS-based molecular ion networking strategy combined with conventional phytochemical procedures. Their chemical structures with absolute configurations were established by spectroscopic data, chemical transformation, electronic circular dichroism calculations, and single-crystal X-ray diffraction analysis. They all contain a rare bicyclo[2.2.2]octene motif. Both forrestiacids J (6) and K (7) represent the first examples of this unique class of [4 + 2]-type hybrids that arose from a normal lanostane-type dienophile. Some isolates remarkably inhibited ATP-citrate lyase (ACL), with IC50 values ranging from 1.8 to 11 µM. Docking studies corroborated the findings by highlighting the interactions between the bioactive compounds and the ACL enzyme (binding affinities: -9.9 to -10.7 kcal/mol). The above findings reveal the important role of protecting plant species diversity in support of chemical diversity and potential sources of new therapeutics.


Assuntos
Diterpenos , Pseudotsuga , Traqueófitas , Triterpenos , Triterpenos/química , Cromatografia Líquida , Espectrometria de Massas em Tandem , Diterpenos/química , Estrutura Molecular
4.
Int J Mol Sci ; 24(18)2023 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-37762525

RESUMO

It has been reported that in an oxidative environment, the flavonoid 2R,3R-dihydroquercetin (2R,3R-DHQ) oxidizes into a product that rearranges to form quercetin. As quercetin is a very potent antioxidant, much better than 2R,3R-DHQ, this would be an intriguing form of targeting the antioxidant quercetin. The aim of the present study is to further elaborate on this targeting. We can confirm the previous observation that 2R,3R-DHQ is oxidized by horseradish peroxidase (HRP), with H2O2 as the oxidant. However, HPLC analysis revealed that no quercetin was formed, but instead an unstable oxidation product. The inclusion of glutathione (GSH) during the oxidation process resulted in the formation of a 2R,3R-DHQ-GSH adduct, as was identified using HPLC with IT-TOF/MS detection. GSH adducts appeared on the B-ring of the 2R,3R-DHQ quinone, indicating that during oxidation, the B-ring is oxidized from a catechol to form a quinone group. Ascorbate could reduce the quinone back to 2R,3R-DHQ. No 2S,3R-DHQ was detected after the reduction by ascorbate, indicating that a possible epimerization of 2R,3R-DHQ quinone to 2S,3R-DHQ quinone does not occur. The fact that no epimerization of the oxidized product of 2R,3R-DHQ is observed, and that GSH adducts the oxidized product of 2R,3R-DHQ on the B-ring, led us to conclude that the redox-modulating activity of 2R,3R-DHQ quinone resides in its B-ring. This could be confirmed by chemical calculation. Apparently, the administration of 2R,3R-DHQ in an oxidative environment does not result in 'biotargeting' quercetin.


Assuntos
Antioxidantes , Quercetina , Antioxidantes/farmacologia , Quercetina/farmacologia , Peróxido de Hidrogênio , Ácido Ascórbico , Glutationa , Quinonas
5.
J Org Chem ; 87(10): 6927-6933, 2022 05 20.
Artigo em Inglês | MEDLINE | ID: mdl-35512323

RESUMO

Liriogerphines A-D (1-4, respectively), an unprecedented class of hybrids of germacranolide-type sesquiterpenoids and aporphine-type alkaloids, were isolated from the rare medicinal plant Liriodendron chinense. Their structures were elucidated by comprehensive spectroscopic analyses combined with electronic circular dichroism calculations and X-ray crystallographic data. Biosynthetically, an aza-Michael addition reaction is proposed to be involved in the assemblies of this class of hybrids. Compound 4 exhibited cytotoxicity against leukemia cells via inducing apoptosis and inhibiting Bcl-2 expression.


Assuntos
Alcaloides , Antineoplásicos , Liriodendron , Sesquiterpenos , Alcaloides/química , Alcaloides/farmacologia , China , Estrutura Molecular , Sesquiterpenos/química , Sesquiterpenos/farmacologia , Árvores
6.
Int J Mol Sci ; 23(19)2022 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-36232887

RESUMO

Linalool showed a broad-spectrum antibacterial effect, but few studies have elucidated the antibacterial mechanism of linalool on Pseudomonas fragi (P. fragi) to date. The present study aimed to uncover the antimicrobial activity and potential mechanism of linalool against P. fragi by determining key enzyme activities and metabolites combined with a high-throughput method and metabolomic pathway analysis. As a result, linalool had excellent inhibitory activity against P. fragi with MIC of 1.5 mL/L. In addition, the presence of linalool significantly altered the intracellular metabolic profile and a total of 346 differential metabolites were identified, of which 201 were up-regulated and 145 were down-regulated. The highlight pathways included beta-alanine metabolism, pantothenic acid and CoA metabolism, alanine, aspartate and glutamate metabolism, nicotinate and nicotinamide metabolism. Overall, linalool could cause metabolic disorders in cells, and the main metabolic pathways involved energy metabolism, amino acid metabolism and nucleic acid metabolism. In particular, the results of intracellular ATP content and related enzymatic activities (ATPase, SDH, and GOT) also highlighted that energy limitation and amino acid disturbance occurred intracellularly. Together, these findings provided new insights into the mechanism by which linalool inhibited P. fragi and theoretical guidance for its development as a natural preservative.


Assuntos
Anti-Infecciosos , Niacina , Ácidos Nucleicos , Pseudomonas fragi , Insuficiência Respiratória , Monoterpenos Acíclicos , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Antibacterianos/metabolismo , Antibacterianos/farmacologia , Anti-Infecciosos/metabolismo , Ácido Aspártico/metabolismo , Coenzima A/metabolismo , Glutamatos/metabolismo , Humanos , Metabolômica , Niacina/metabolismo , Niacinamida/metabolismo , Ácidos Nucleicos/metabolismo , Ácido Pantotênico , Pseudomonas fragi/metabolismo
7.
Molecules ; 27(9)2022 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-35566340

RESUMO

Coconut (Cocos nucifera L.) is one of the most critical economic crops in the tropics and sub-tropics. Although coconut protein has attracted more and more attention due to its nutritional potential, the lack of proteomic information has limited its practical application. The present study aimed to investigate the coconut meat proteome by shotgun proteomics and protein-based bioinformatic analysis. A grand total of 1686 proteins were identified by searching the National Center for Biotechnology Information (NCBI) protein database and self-constructed C. nucifera transcriptome repository. Among them, 17 and 9 proteins were identified as antioxidant proteins and globulins, respectively. Network analysis of the globulins referred to the sub-works of Cupin and Oleosin, and the antioxidant proteins were related to the sub-networks of glutathione metabolism and peroxisome. The bioactive peptides acquired by in-silico digestion of the targeted proteins have the potential to be applied as antioxidants and emulsifiers for both healthcare and food stabilization.


Assuntos
Cocos , Proteômica , Antioxidantes/metabolismo , Antioxidantes/farmacologia , Cocos/metabolismo , Biologia Computacional , Proteínas de Plantas/metabolismo
8.
World J Microbiol Biotechnol ; 38(4): 56, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-35165818

RESUMO

Pseudomonas aeruginosa (P. aeruginosa) is the dominant spoilage bacterium in cold fresh beef. The current strategy is undertaken to overcome the low water solubility of linalool by encapsulating linalool into emulsions. The results of field emission scanning electron microscopy and particle size distribution revealed that the appearance of the bacterial cells was severely disrupted after exposure to linalool emulsion (LE) with an minimum inhibitory concentration (MIC) of 1.5 mL/L. Probes combined with fluorescence spectroscopy were performed to detect cell membrane permeability, while intracellular components (protein and ion leakage) and crystal violet staining were further measured to characterize cell membrane integrity and biofilm formation ability. The results confirmed that LE could destroy the structure of the cell membrane, thereby leading to the leakage of intracellular material and effective removal of biofilms. Molecular docking confirmed that LE can interact with the flagellar cap protein (FliD) and DNA of P. aeruginosa, inhibiting biofilm formation and causing genetic damage. Furthermore, the results of respiratory metabolism and reactive oxygen species (ROS) accumulation revealed that LE could significantly inhibit the metabolic activity of P. aeruginosa and induce oxidative stress. In particular, the inhibition rate of LE on P. aeruginosa was 23.03% and inhibited mainly the tricarboxylic acid cycle (TCA). Finally, LE was applied to preserve cold fresh beef, and the results showed that LE could effectively inhibit the activity of P. aeruginosa and delay the quality change of cold fresh beef during the storage period. These results are of great significance to developing natural preservatives and extending the shelf life of cold fresh beef.


Assuntos
Antibacterianos , Pseudomonas aeruginosa , Monoterpenos Acíclicos , Animais , Antibacterianos/farmacologia , Biofilmes , Bovinos , Emulsões , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular
9.
Curr Microbiol ; 78(5): 1730-1740, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33704531

RESUMO

Washing rice water (WRW) refers to the sewage produced by rice washing in China and other parts of Asia people's daily life. As in the WRW is rich a variety of nutrients, microorganisms are prone to multiply and pollute the environment. In this article, high-throughput sequencing is used to describe the microbial diversity in different fermentation time WRW. The results showed that the sequencing depth effectively covered the microbial species in the samples, and the bacterial community structure in the samples of WRW at different fermentation periods was rich in diversity. Preominant taxa included Proteobacteria (62%), Firmicutes (28%), approximately Cyanobacteria (10%) and Bacteroidetes (0.5%). The core WRW microbiome comprises Trabulsiella, Pseudomonas, Serratia, Lactobacillus, Erwinia, Enterobacter, Clostridium and Acinetobacter, some of which are potential beneficial microbes. The change of microbial community composition with the change of habitat was assessed. It was found that environmental factors had significant influence on the assembly structure of microbial community.


Assuntos
Microbiota , Oryza , China , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Água
10.
Molecules ; 26(1)2021 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-33466475

RESUMO

The demand for reduced chemical preservative usage is currently growing, and natural preservatives are being developed to protect seafood. With its excellent antibacterial properties, linalool has been utilized widely in industries. However, its antibacterial mechanisms remain poorly studied. Here, untargeted metabolomics was applied to explore the mechanism of Shewanella putrefaciens cells treated with linalool. Results showed that linalool exhibited remarkable antibacterial activity against S. putrefaciens, with 1.5 µL/mL minimum inhibitory concentration (MIC). The growth of S. putrefaciens was suppressed completely at 1/2 MIC and 1 MIC levels. Linalool treatment reduced the membrane potential (MP); caused the leakage of alkaline phosphatase (AKP); and released the DNA, RNA, and proteins of S. putrefaciens, thus destroying the cell structure and expelling the cytoplasmic content. A total of 170 differential metabolites (DMs) were screened using metabolomics analysis, among which 81 species were upregulated and 89 species were downregulated after linalool treatment. These DMs are closely related to the tricarboxylic acid (TCA) cycle, glycolysis, amino acid metabolism, pantothenate and CoA biosynthesis, aminoacyl-tRNA biosynthesis, and glycerophospholipid metabolism. In addition, linalool substantially affected the activity of key enzymes, such as succinate dehydrogenase (SDH), pyruvate kinase (PK), ATPase, and respiratory chain dehydrogenase. The results provided some insights into the antibacterial mechanism of linalool against S. putrefaciens and are important for the development and application of linalool in seafood preservation.


Assuntos
Monoterpenos Acíclicos/farmacologia , Antibacterianos/farmacologia , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Infecções por Bactérias Gram-Negativas/tratamento farmacológico , Metaboloma/efeitos dos fármacos , Shewanella putrefaciens/efeitos dos fármacos , Infecções por Bactérias Gram-Negativas/metabolismo , Infecções por Bactérias Gram-Negativas/microbiologia , Inseticidas/farmacologia , Shewanella putrefaciens/crescimento & desenvolvimento , Shewanella putrefaciens/metabolismo
11.
Molecules ; 26(9)2021 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-34068822

RESUMO

The contribution of rheological properties and viscoelasticity of the interfacial adsorbed layer to the emulsification mechanism of enzymatic modified sugar beet pectin (SBP) was studied. The component content of each enzymatic modified pectin was lower than that of untreated SBP. Protein and ferulic acid decreased from 5.52% and 1.08% to 0.54% and 0.13%, respectively, resulting in a decrease in thermal stability, apparent viscosity, and molecular weight (Mw). The dynamic interfacial rheological properties showed that the interfacial pressure and modulus (E) decreased significantly with the decrease of functional groups (especially proteins), which also led to the bimodal distribution of particle size. These results indicated that the superior emulsification property of SBP is mainly determined by proteins, followed by ferulic acid, and the existence of other functional groups also promotes the emulsification property of SBP.


Assuntos
Beta vulgaris/química , Emulsões/química , Enzimas/metabolismo , Pectinas/metabolismo , Reologia , Adsorção , Difusão , Elasticidade , Cinética , Peso Molecular , Óleos/química , Tamanho da Partícula , Pressão , Espectroscopia de Prótons por Ressonância Magnética , Espectroscopia de Infravermelho com Transformada de Fourier , Eletricidade Estática , Termogravimetria , Fatores de Tempo , Viscosidade , Água/química
12.
Microb Pathog ; 141: 103980, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31962183

RESUMO

The purpose of this study was to evaluate the antibacterial activity and mechanism of linalool against Pseudomonas aeruginosa. The determination of antibacterial activity was based on the minimum inhibitory concentration (MIC) and the minimum bactericide concentration (MBC). Further, the antibacterial mechanism was explored by a growth curve assay, scanning electron microscopy (SEM), cell membrane permeability, membrane potential and respiratory chain dehydrogenase determination. The MIC and the MBC of linalool were 431 µg/mL and 862 µg/mL, respectively. The growth curve assay showed that the growth of P. aeruginosa was inhibited. The results of SEM revealed that linalool disrupted the normal morphology of the cell. The release of nucleic acids as well as the decrease in the membrane potential proved that the membrane integrity of P. aeruginosa was destroyed. Moreover, the respiratory chain was damaged by respiratory chain dehydrogenase determination as the absorbance at 490 nm decreased. This research suggested that it was possible for linalool to become a preservative of food by destroying the cell membrane, resulting in cell death.


Assuntos
Monoterpenos Acíclicos/farmacologia , Antibacterianos/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Complexo I de Transporte de Elétrons/metabolismo , Potenciais da Membrana/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Mitocôndrias/efeitos dos fármacos , Pseudomonas aeruginosa/ultraestrutura
13.
Molecules ; 25(3)2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-32033016

RESUMO

Vitamin E (VE) and ß-cyclodextrin (ß-CD) can form an inclusion complex; however, the inclusion rate is low because of the weak interaction between VE and ß-CD. The results of a molecular docking study showed that the oxygen atom in the five-membered ring of octenyl succinic anhydride (OSA) formed a strong hydrogen bond interaction (1.89 Å) with the hydrogen atom in the hydroxyl group of C-6. Therefore, ß-CD was modified using OSA to produce octenyl succinic-ß-cyclodextrin (OCD). The inclusion complexes were then prepared using OCD with VE. The properties of the inclusion complex were investigated by Fourier-transform infrared spectroscopy (FT-IR), 13C CP/MAS NMR, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results demonstrated that VE had been embedded into the cavity of OCD. Furthermore, the emulsifying properties (particle size distribution, ζ-potential, and creaming index) of the OCD/VE inclusion-complex-stabilized emulsion were compared with that stabilized by ß-CD, OCD, and an OCD/VE physical mixture. The results showed that the introduction of the OS group and VE could improve the physical stability of the emulsion. In addition, the OCD/VE inclusion complex showed the strongest ability to protect the oil in the emulsion from oxidation. OCD/VE inclusion complex was able to improve the physical and oxidative stability of the emulsion, which is of great significance to the food industry.


Assuntos
Emulsões/química , Conservação de Alimentos/métodos , Succinatos/química , Vitamina E/química , beta-Ciclodextrinas/química , Antioxidantes/química , Indústria Alimentícia/métodos , Peroxidação de Lipídeos/efeitos dos fármacos , Microscopia de Força Atômica , Simulação de Acoplamento Molecular , Ressonância Magnética Nuclear Biomolecular , Espectroscopia de Infravermelho com Transformada de Fourier
14.
Molecules ; 25(1)2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31861877

RESUMO

Limonene is a monoterpenoid compound, which is founded in a lot of plants' essential oils with good antibacterial activity against food-borne pathogens, but it has an ambiguous antimicrobial susceptibility and mechanism against Listeria monocytogenes (L. monocytogenes). In this study, the antimicrobial susceptibility of Limonene to L. monocytogenes was studied, and some new sights regarding its antibacterial mechanism were further explored. Scanning electron microscopy (SEM) verified that limonene caused the destruction of the cell integrity and wall structure of L. monocytogenes. The increase in conductivity and the leakage of intracellular biomacromolecules (nucleic acids and proteins) confirmed that limonene had an obvious effect on cell membrane permeability. The results of Propidium Iodide (PI) fluorescence staining were consistent with the results of the conductivity measurements. This indicated that limonene treatment caused damage to the L. monocytogenes cell membrane. Furthermore, the decrease in ATP content, ATPase (Na+K+-ATPase, Ca2+-ATPase) activity and respiratory chain complex activity indicated that limonene could hinder ATP synthesis by inhibiting the activity of the respiratory complex and ATPase. Finally, differential expression of proteins in the respiratory chain confirmed that limonene affected respiration and energy metabolism by inhibiting the function of the respiratory chain complex.


Assuntos
Antibacterianos/farmacologia , Permeabilidade da Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Limoneno/farmacologia , Listeria monocytogenes/metabolismo , Óleos Voláteis/química , Antibacterianos/química , Limoneno/química
15.
Molecules ; 24(23)2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31795169

RESUMO

The aim of this study was to develop a nondairy fermented product based on mango slurry. Lactobacillus plantarum and Saccharomyces cerevisiae DV10 were used as starter cultures in single and co-cultivations. The microbial populations and metabolites produced during mango slurry fermentation were investigated. At the end of all fermentations, the bacterial populations were higher than 6.0 log CFU/mL. Lactic acid was the main organic acid produced, achieving up to 6.12 g/L after 24 h in co-culture with L. plantarum and S. cerevisiae DV10. Volatile compounds were determined after 24 h of fermentation, the co-cultures of L. plantarum and S. cerevisiae DV10 could decrease terpenes and produce alcohols and esters. The co-cultivations obtained the most total phenolics as well as showed the strongest 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging activity, ferric-reducing antioxidant power (FRAP) and low-density lipoprotein (LDL) oxidation inhibition. Hence, a high-bioactivity probiotic product was successfully obtained via mango slurry fermentation inoculated with a co-culture of L. plantarum and S. cerevisiae DV10.


Assuntos
Fermentação , Lactobacillus plantarum/metabolismo , Mangifera/química , Saccharomyces cerevisiae/metabolismo , Antioxidantes/química , Antioxidantes/farmacologia , Microbiologia de Alimentos , Oxirredução , Compostos Orgânicos Voláteis/química , Compostos Orgânicos Voláteis/farmacologia
16.
Molecules ; 24(23)2019 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-31795396

RESUMO

The aim of this study was to prepare sodium alginates (SAs) with different molecular weight and G/M ratio, and characterize their rheological behaviors and emulsifying properties. The result of Fourier transform infrared (FTIR) showed that the chemical bonds among the ß-d-mannuronic acid- (M-), α-l-guluronic acid- (G-), and MG-sequential blocks in the SA chains were not changed significantly by acid treatment. Meanwhile, the molecular weight and G/M ratio of the SA exhibited drastic variation after acid modification. The result of rheological analysis suggesting that the apparent viscosity of SA reduced from 30 to 16.4 mPa.s with the increase of shear rate, reveals that SA solution belongs to pseudoplastic liquid. Also, the apparent viscosity of acid-modified SA solution dropped rapidly with the decrease of the molecular weight. The properties of emulsions stabilized by SA, SA-Ms, and commercial SAs were evaluated via the interface tensiometry and determination of the zeta potential, droplet size, creaming index (CI), and Turbiscan stability index (TSI). Compared with the SA-stabilized emulsion, the interfacial tension of the emulsion stabilized by SA-M increased with the decrease of the molecular weight reduced at the similar M/G ratio. The decrease in zeta potential and the increase in TSI of the emulsion were observed with the decrease of molecular weight, indicating that molecular weight plays an important role on the emulsifying ability of SA. In addition, the SA with low G/M ratio can form emulsions with stable and fine droplets.


Assuntos
Alginatos/química , Ácidos Hexurônicos/química , Emulsões , Reologia
17.
Molecules ; 24(18)2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31489899

RESUMO

3-Carene is an antimicrobial monoterpene that occurs naturally in a variety of plants and has an ambiguous antibacterial mechanism against food-borne germs. The antibacterial effects and action mechanism of 3-carene against Gram-positive Brochothrix thermosphacta ACCC 03870 and Gram-negative Pseudomonas fluorescens ATCC 13525 were studied. Scanning electron microscopy (SEM) examination and leakage of alkaline phosphatase (AKP) verified that 3-carene caused more obvious damage to the morphology and wall structure of B. thermosphacta than P. fluorescens. The release of potassium ions and proteins, the reduction in membrane potential (MP), and fluorescein diacetate (FDA) staining further confirmed that the loss of the barrier function of the cell membrane and the leakage of cytoplasmic contents were due to the 3-carene treatment. Furthermore, the disorder of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and ATP content indicated that 3-carene could lead to metabolic dysfunction and inhibit energy synthesis. In addition, the results from the fluorescence analysis revealed that 3-carene could probably bind to bacterial DNA and affect the conformation and structure of genomic DNA. These results revealed that 3-carene had strong antibacterial activity against B. thermosphacta and P. fluorescens via membrane damage, bacterial metabolic perturbations, and genomic DNA structure disruption, interfering in cellular functions and even causing cell death.


Assuntos
Antibacterianos/farmacologia , Monoterpenos Bicíclicos/farmacologia , Brochothrix/efeitos dos fármacos , Pseudomonas fluorescens/efeitos dos fármacos , Brochothrix/genética , Parede Celular/efeitos dos fármacos , DNA Bacteriano/química , DNA Bacteriano/efeitos dos fármacos , Microbiologia de Alimentos , Potenciais da Membrana/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Varredura , Pseudomonas fluorescens/genética
18.
Molecules ; 23(9)2018 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-30223615

RESUMO

Tomato juice was fermented by Lactobacillus plantarum and Lactobacillus casei to produce an innovative high-bioactivity probiotic beverage. The levels of lycopene, total carotenoids, ascorbic acid, total phenolic and volatile compounds, 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-3-ethylbenzotiazo-line-6-sulfonic acid (ABTS) radical scavenging capacities, ferric reducing antioxidant power (FRAP), and Escherichia coli flora, as well as the inhibition of copper-induced human low-density lipoproteins (LDL)-cholesterol oxidation assays, were measured. The results revealed that the ABTS and DPPH inhibition values, as well as the FRAP and total phenolic content, were significantly increased. LDL-cholesterol oxidation was markedly delayed after the addition of the fermented juice. The in vitro inhibitory effects of Escherichia coli flora were substantially increased after being fermented with Lactobacillus plantarum and Lactobacillus casei. The results associated with the volatile compounds indicated that fermentation with Lactobacillus plantarum and Lactobacillus casei is a meaningful strategy for modifying flavors.


Assuntos
Sucos de Frutas e Vegetais/microbiologia , Lacticaseibacillus casei/fisiologia , Lactobacillus plantarum/fisiologia , Solanum lycopersicum/química , Anti-Infecciosos/análise , Antioxidantes/análise , LDL-Colesterol/metabolismo , Escherichia coli/crescimento & desenvolvimento , Fermentação , Sucos de Frutas e Vegetais/análise , Humanos , Probióticos
19.
Molecules ; 23(10)2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30308985

RESUMO

Concentrated coconut milk (CCM), a raw material from coconut products, is extremely unstable because of its high oil content (>30%). In this study, three model emulsions-primary emulsions stabilized by coconut proteins only, secondary emulsions stabilized by the conjugation of sugar beet pectin (SBP) and coconut protein, and laccase-treated secondary emulsions-were prepared to investigate the effects of different factors (coconut proteins, coconut proteins + SBP, laccase-treated emulsions) on the stability of model emulsions and the application of this method to real CCM. The stability of the emulsions was evaluated based on their interfacial tension, zeta potential, particle size distribution, rheological properties, and the assembly formation of SBP and coconut protein at the oil⁻water interface. Results showed that addition of SBP or laccase can increase the viscosity and reduce the interfacial tension of the emulsion, and the effect was concentration dependent. Zeta potential of the emulsion decreased with the increase of protein (from -16 to -32 mV) and addition of SBP (from -32 to -46 mV), and it was reduced when laccase was added (from -9.5 to -6.0 mV). The secondary emulsion exhibited the narrowest particle size distribution (from 0.1 to 20 µm); however, laccase-catalyzed secondary emulsions showed the best storage stability and no layering when the laccase content reached 10 U/100 g. Confocal laser scanning microscopy (CLSM) revealed that protein was adsorbed on the oil⁻water interface and SBP distributed in the continuous phase could undergo oxidative crosslinking by laccase. These results show that the stability of the concentrated emulsion can be effectively improved by adding SBP and laccase.


Assuntos
Beta vulgaris/química , Cocos/química , Emulsões/química , Lacase/farmacologia , Pectinas/farmacologia , Tamanho da Partícula , Reologia , Eletricidade Estática , Tensão Superficial , Fatores de Tempo
20.
J Food Sci Technol ; 55(3): 964-976, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29487438

RESUMO

Matured coconut water (MCW) is a by-product in the coconut milk industry that is usually discarded due to its unpleasant flavor. In this study, low-alcohol coconut water (LACW) was fermented with Saccharomyces cerevisiae to improve the quality of MCW. Volatile components and nonvolatile flavor-related elements were estimated to compare the qualities of the MCW and LACW. Besides measuring the kinetic changes, the levels of fructose, glucose, sucrose and ethanol contents were also determined. The results of the organic acid assays showed that tartaric, pyruvic and succinic acids were the primary organic acids present in LACW and increased significantly with fermentation. The resulting volatile composition assay indicated that esters, alcohols and fatty acids were significantly influenced by fermentation and yeast strains. Moreover, 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), cupric ion reducing antioxidant capacity and ferric reducing antioxidant power values increased significantly throughout the process, correlating with the enhancement of total phenolic content.

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