Antibacterial mechanism and activities of black pepper chloroform extract

Dietary anti-inflammatory and anti-bacterial medicinal plants and its compounds in bovine mastitis associated impact on human life

Bovine mastitis (BM) is the most common bacterial mediated inflammatory disease in the dairy cattle that causes huge economic loss to the dairy industry due to decreased milk quality and quantity. Milk is the essential food in the human diet, and rich in crucial nutrients that helps in lowering the risk of diseases like hypertension, cardiovascular diseases and type 2 diabetes. The main causative agents of the disease include various gram negative, and positive bacteria, along with other risk factors such as udder shape, age, genetic, and environmental factors also contributes much for the disease. Currently, antibiotics, immunotherapy, probiotics, dry cow, and lactation therapy are commonly recommended for BM. However, these treatments can only decrease the rise of new cases but can't eliminate the causative agents, and they also exhibit several limitations. Hence, there is an urgent need of a potential source that can generate a typical and ideal treatment to overcome the limitations and eliminate the pathogens. Among the various sources, medicinal plants and its derived products always play a significant role in drug discovery against several diseases. In addition, they are also known for its low toxicity and minimum resistance features. Therefore, plants and its compounds that possess anti-inflammatory and anti-bacterial properties can serve better in bovine mastitis. In addition, the plants that are serving as a food source and possessing pharmacological properties can act even better in bovine mastitis. Hence, in this evidence-based study, we particularly review the dietary medicinal plants and derived products that are proven for anti-inflammatory and anti-bacterial effects. Moreover, the role of each dietary plant and its compounds along with possible role in the management of bovine mastitis are delineated. In this way, this article serves as a standalone source for the researchers working in this area to help in the management of BM.

Activity-based protein profiling technology reveals malate dehydrogenase as the target protein of cinnamaldehyde against Aspergillus niger

Cinnamaldehyde displays strong antifungal activity against fungi such as Aspergillus niger, but its precise molecular mechanisms of antifungal action remain inadequately understood. In this investigation, we applied chemoproteomics and bioinformatic analysis to unveil the target proteins of cinnamaldehyde in Aspergillus niger cells. Additionally, our study encompassed the examination of cinnamaldehyde's effects on cell membranes, mitochondrial malate dehydrogenase activity, and intracellular ATP levels in Aspergillus niger cells. Our findings suggest that malate dehydrogenase could potentially serve as an inhibitory target of cinnamaldehyde in Aspergillus niger cells. By disrupting the activity of malate dehydrogenase, cinnamaldehyde interferes with the mitochondrial tricarboxylic acid (TCA) cycle, leading to a significant decrease in intracellular ATP levels. Following treatment with cinnamaldehyde at a concentration of 1 MIC, the inhibition rate of MDH activity was 74.90 %, accompanied by an 84.5 % decrease in intracellular ATP content. Furthermore, cinnamaldehyde disrupts cell membrane integrity, resulting in the release of cellular contents and subsequent cell demise. This study endeavors to unveil the molecular-level antifungal mechanism of cinnamaldehyde via a chemoproteomics approach, thereby offering valuable insights for further development and utilization of cinnamaldehyde in preventing and mitigating food spoilage.

Potato glycoside alkaloids exhibit antifungal activity by regulating the tricarboxylic acid cycle pathway of Fusarium solani

Fusarium solani is a pathogenic fungus that causes significant harm, leading to crop yield reduction, fruit quality reduction, postharvest decay, and other diseases. This study used potato glycoside alkaloids (PGA) as inhibitors to investigate their effects on the mitochondrial structure and tricarboxylic acid (TCA) cycle pathway of F. solani. The results showed that PGA could inhibit the colony growth of F. solani (54.49%), resulting in the disappearance of the mitochondrial membrane and the loss of contents. PGA significantly decreased the activities of aconitase (ACO), isocitrate dehydrogenase (IDH), α-ketoglutarate dehydrogenase (α-KGDH), succinate dehydrogenase (SDH), fumarase (FH), malate dehydrogenase (MDH), succinyl-CoA synthetase (SCS), and increased the activity of citrate synthase (CS) in F. solani. After PGA treatment, the contents of acetyl coenzyme A (CoA), citric acid (CA), malic acid (L-MA), and α-ketoglutaric acid (α-KG) in F. solani were significantly decreased. The contents of isocitric acid (ICA), succinyl coenzyme A (S-CoA), succinic acid (SA), fumaric acid (FA), and oxaloacetic acid (OA) were significantly increased. Transcriptomic analysis showed that PGA could significantly affect the expression levels of 19 genes related to TCA cycle in F. solani. RT-qPCR results showed that the expression levels of ACO, IDH, α-KGDH, and MDH-related genes were significantly down-regulated, and the expression levels of SDH and FH-related genes were significantly up-regulated, which was consistent with the results of transcriptomics. In summary, PGA can achieve antifungal effects by reducing the tricarboxylic acid cycle's flow and regulating key genes' expression levels. This study reveals the antifungal mechanism of PGA from the perspective of TCA cycle, and provides a theoretical basis for the development and application of PGA as a biopesticide.

Inhibition of Food-Borne Pathogen Growth and Biogenic Amine Synthesis by Spice Extracts

Food-borne pathogens and their toxins cause significant health problems in humans. Formation of biogenic amines (BAs) produced by microbial decarboxylation of amino acids in food is undesirable because it can induce toxic effects in consumers. Therefore, it is crucial to investigate the effects of natural additives with high bioactivity like spice extracts to inhibit the growth of these bacteria and the formation of BAs in food. In the present study, the antibacterial effects of diethyl ether spice (sumac, cumin, black pepper, and red pepper) extracts at doses of 1% (w/v) on Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa, Campylobacter jejuni, Aeromonas hydrophila, Salmonella Paratyphi A, and Yersinia enterocolitica) food-borne pathogen bacterial strains (FBP) were established. In addition, the accumulation of ammonia (AMN), trimethylamine (TMA), and biogenic amines (BAs) in tyrosine decarboxylase broth (TDB) was investigated by using high performance liquid chromatography (HPLC). Sumac extract exhibited the highest antibacterial potential against all FBPs, followed by cumin and peppers. AMN (570.71 mg/L) and TMA (53.66 mg/L) production were strongly inhibited by sumac extract in the levels of 55.10 mg/L for Y. enterocolitica and 2.76 mg/L for A. hydrophila, respectively. With the exception of S. aureus, black pepper dramatically reduced the synthesis of putrescine, serotonin, dopamine, and agmatine by FBP especially for Gram-negative ones. Furthermore, sumac extracts inhibited histamine and tyramine production by the majority of FBP. This research suggests the application of sumac extracts as natural preservatives for inhibiting the growth of FBPs and limiting the production of AMN, TMA, and BAs.

Inhibitory effect of tannic acid on the growth of Apiospora arundinis and 3-Nitropropionic acid production

AIMS

This study aimed to investigate the inhibitory effect of tannic acid (TA) on the growth of Apiospora arundinis and 3-Nitropropionic acid (3-NPA) production.

METHODS AND RESULTS

To investigate the antifungal mechanism, the effects of TA on the hypha growth, electrical conductivity, hypha morphology, defense-related enzymes, and 3-NPA production of A. arundinis were studied. TA concentrations of 640 and 1280 μg ml-1 exhibited strong antifungal activity against A. arundinis. The results of scanning electron microscopy and transmission electron microscopy showed that the hypha of the A. arundinis was severely deformed after TA treatment, and the cell membrane was blurred and thin, vacuoles were obviously shrunken and smaller, and most of the organelles were decomposed into irregular fragments. The increased electrical conductivity and malondialdehyde content indicated that TA caused peroxidation of unsaturated fatty acids and damaged the structure of the cell membrane. The decrease of intracellular ATPase and succinate dehydrogenase content indicated that TA damaged the function of mitochondria, and participated in the inhibition of respiratory metabolism. In addition, TA significantly reduced 3-NPA production and completely inhibited 3-NPA production at 640 and 1280 μg ml-1.

CONCLUSION

TA effectively inhibited both growth of A. arundinis in vitro and 3-NPA production.

Functional Characterization of Aldehyde Dehydrogenase in Fusarium graminearum

Aldehyde dehydrogenase (ALDH), a common oxidoreductase in organisms, is an aldehyde scavenger involved in various metabolic processes. However, its function in different pathogenic fungi remains unknown. Fusarium graminearum causes Fusarium head blight in cereals, which reduces grain yield and quality and is an important global food security problem. To elucidate the pathogenic mechanism of F. graminearum, seven genes encoding ALDH were knocked out and then studied for their function. Single deletions of seven ALDH genes caused a decrease in spore production and weakened the pathogenicity. Furthermore, these deletions altered susceptibility to various abiotic stresses. FGSG_04194 is associated with a number of functions, including mycelial growth and development, stress sensitivity, pathogenicity, toxin production, and energy metabolism. FGSG_00139 and FGSG_11482 are involved in sporulation, pathogenicity, and SDH activity, while the other five genes are multifunctional. Notably, we found that FGSG_04194 has an inhibitory impact on ALDH activity, whereas FGSG_00979 has a positive impact. RNA sequencing and subcellular location analysis revealed that FGSG_04194 is responsible for biological process regulation, including glucose and lipid metabolism. Our results suggest that ALDH contributes to growth, stress responses, pathogenicity, deoxynivalenol synthesis, and mitochondrial energy metabolism in F. graminearum. Finally, ALDH presents a potential target and theoretical basis for fungicide development.

Piperine-Loaded In Situ Gel: Formulation, In Vitro Characterization, and Clinical Evaluation against Periodontitis

Periodontitis is an inflammatory disorder associated with dysbiosis and characterized by microbiologically related, host-mediated inflammation that leads to the damage of periodontal tissues including gingiva, connective tissues, and alveolar bone. The aim of this study was to develop an in situ gel consisting of piperine. Eight in situ gel formulations were designed by varying the concentration of deacylated gellan gum cross-linked with sodium tripolyphosphate, and poloxamer-407. The prepared gels were evaluated for gelation temperature, gelation time, viscosity, piperine-loading efficiency, and piperine release. Finally, the optimized formula was evaluated for anti-inflammatory effectiveness among human patients during a 14-day follow-up. The optimized in situ gel formulation exhibited a gelation temperature of 35 ± 1 °C, gelling of 36 ± 1 s, excellent syringeability, and piperine loading of 95.3 ± 2.3%. This formulation efficiently sustained in vitro drug release for up to 72 h. In vivo studies revealed an efficient sol-to-gel transformation of optimized in situ gel formulation at physiological conditions, permitting an efficient residence time of the formulation within a periodontitis pocket. Most importantly, a clinical study revealed that treatment with the optimized formulation elicited a significant reduction in the mean plaque score (p = 0.001), gingival index (p = 0.003), and pocket depth (p = 0.002), and exerted a potent anti-inflammatory potential, compared to the control group. Collectively, piperine-loaded in situ gel might represent a viable therapeutic approach for the management of gingival and periodontal diseases.

Enhanced inactivation of Escherichia coli by ultrasound combined with peracetic acid during water disinfection

Peracetic acid (PAA) is a desirable disinfectant for municipal wastewater because of its potent disinfection performance and limited toxic by-products. This study explored the efficiency and mechanism of Escherichia coli inactivation by PAA combined with ultrasound simultaneously (ultrasound + PAA) or (ultrasound → PAA) sequentially. The result showed that 60 kHz ultrasound combined with PAA sequentially (60 kHz → PAA) had excellent inactivation performance on E. coli, up to 4.69-log₁₀. The result also showed that the increase of pH and humic acid concentration in solution significantly reduced the inactivation efficiency of 60 kHz → PAA treatment. We also observed that the increase of temperature was beneficial to the disinfection, while anions (Cl^-; HCO₃^-) had little effect. With 60 kHz → PAA, the PAA and the synergism between PAA and ultrasound played major contribution to the inactivation, which we assumed might be due to both the diffusion of PAA into the cells and the damage to the cytomembrane by ultrasound, as evidenced through the laser confocal microscopy (LSCM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The inactivation mechanism involved the destruction of cell membrane and loss of intracellular material. Empirically, 60 kHz → PAA was found to be effective for the inactivation of E. coli in actual wastewater, and the regrowth potential of E. coli treated by 60 kHz → PAA was significantly lower than that treated only by PAA.

Physiological and transcriptome analysis of Candida albicans in response to X33 antimicrobial oligopeptide treatment

Introduction

Candida albicans is an opportunistic pathogenic fungus, which frequently causes systemic or local fungal infections in humans. The evolution of its drug-resistant mutants necessitate an urgent development of novel antimicrobial agents.

Results

Here, we explored the antimicrobial activity and inhibitory mechanisms of X33 antimicrobial oligopeptide (X33 AMOP) against C. albicans. The oxford cup test results showed that X33 AMOP had strong inhibitory activity against C. albicans, and its MIC and MFC were 0.625 g/L and 2.5 g/L, respectively. Moreover, SEM and TEM showed that X33 AMOP disrupted the integrity of cell membrane. The AKP, ROS, H₂O₂ and MDA contents increased, while the reducing sugar, soluble protein, and pyruvate contents decreased after the X33 AMOP treatment. This indicated that X33 AMOP could damage the mitochondrial integrity of the cells, thereby disrupting the energy metabolism by inducing oxidative stress in C. albicans. Furthermore, transcriptome analysis showed that X33 AMOP treatment resulted in the differential expression of 1140 genes, among which 532 were up-regulated, and 608 were down-regulated. These DEGs were related to protein, nucleic acid, and carbohydrate metabolism, and their expression changes were consistent with the changes in physiological characteristics. Moreover, we found that X33 AMOP could effectively inhibit the virulence attributes of C. albicans by reducing phospholipase activity and disrupting hypha formation.

Discussion

These findings provide the first-ever detailed reference for the inhibitory mechanisms of X33 AMOP against C. albicans and suggest that X33 AMOP is a potential drug candidate for treating C. albicans infections.

Inhibition of Cronobacter sakazakii by Litsea cubeba Essential Oil and the Antibacterial Mechanism

Litsea cubeba essential oil (LC-EO) has anti-insecticidal, antioxidant, and anticancer proper-ties; however, its antimicrobial activity toward Cronobacter sakazakii has not yet been researched extensively. The objective of this study was to investigate the antimicrobial and antibiofilm effects of LC-EO toward C. sakazakii, along with the underlying mechanisms. The minimum inhibitory concentrations of LC-EO toward eight different C. sakazakii strains ranged from 1.5 to 4.0 μL/mL, and LC-EO exposure showed a longer lag phase and lower specific growth compared to untreated bacteria. LC-EO increased reactive oxygen species production, decreased the integrity of the cell membrane, caused cell membrane depolarization, and decreased the ATP concentration in the cell, showing that LC-EO caused cellular damage associated with membrane permeability. LC-EO induced morphological changes in the cells. LC-EO inhibited C. sakazakii in reconstituted infant milk formula at 50 °C, and showed effective inactivation of C. sakazakii biofilms on stainless steel surfaces. Confocal laser scanning and attenuated total reflection-Fourier-transform infrared spectrometry indicated that the biofilms were disrupted by LC-EO. These findings suggest a potential for applying LC-EO in the prevention and control of C. sakazakii in the dairy industry as a natural antimicrobial and antibiofilm agent.

A review of plant antipathogenic constituents: Source, activity and mechanism

Green prevention and control of plant pathogens is a development direction of sustainable and low-carbon agriculture given the limitation of traditional chemicals. Plant-derived antipathogenic constituents (PAPCs) exhibit the advantages of being environmental benign and a broad spectrum of target pathogens over traditional chemicals. Here, we review the research advances on plant sources, chemical compositions, activities of antipathogenic constituents in the past 20 years. Reported PAPCs are classified into categories of phenols, flavonoids, terpenoids, alkaloids and antimicrobial peptides. Angiosperms, gymnosperms and some lower plants are the main plant source of detected PAPCs. The PAPCs act on pathogens through multiple pathways including destroying cell structures, blocking key composition synthesis and inhibiting cell metabolism. The development trends of PAPCs are finally prospected. This review serves as a comprehensive review on the study of plant antipathogenic constituents and a key reference for forecasting the source, characteristic and activity of PAPC.

Understand the antibacterial behavior and mechanism of hydrothermal wastewater

Unlocking the antibacterial potential is an emerging strategy to valorizing the toxic wastewater from hydrothermal liquefaction (HTL). Here, we investigated the response and biological mechanism of antibacterial properties of HTL wastewater. Four different biowastes i.e. microalgae, cornstalk, cow manure and swine manure were used as the feedstock of HTL to create wastewater with diverse molecule spectrum, whereas ten strains i.e. five gram-positive strains and five gram-negative strains were employed to represent typical pathogenic microorganism. HTL wastewater exhibited antibacterial potential and obvious reduction on cell viability at high inclusion ratio, although the minimum inhibitory concentration (MIC) and cell response intensity varied depending on different HTL feedstocks and strain species. The decreased ATP generation and increased H₂O₂ accumulation in treated cells further confirmed the inhibition of HTL wastewater on the cell metabolism. The antibacterial mechanism of HTL wastewater was confirmed, including damage to biomolecules or membranes, depletion of crucial components, disruption of metabolic circuits and imbalance of creation of redox cofactor. The complex compounds in HTL wastewater were probably attributed to the multiple inhibition pathways and the relationship among those multiple pathways was speculated. The present study contributes to the mechanism analysis of complex compound mixture and bactericide characteristics of HTL wastewater.

Metabolomics analysis and membrane damage measurement reveal the antibacterial mechanism of lipoic acid against Yersinia enterocolitica

Yersinia enterocolitica is a pathogenic microorganism that can cause food-borne diseases. Lipoic acid (LA) has been used as an antioxidant against bacteria, but its antibacterial mechanism is rarely reported. This study aims to explore the antibacterial mechanism of LA and its effect on the metabolites of Y. enterocolitica through membrane damage and metabolomics analysis. The results showed that the minimum inhibitory concentration (MIC) of LA against Y. enterocolitica was 2.5 mg mL^-1. The membrane potential was depolarized, and intracellular pH (pH_in) and ATP were significantly reduced, indicating that LA destroys the cell membrane structure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) further confirmed LA-induced cell membrane damage. The metabolic profile of Y. enterocolitica following LA treatment was analyzed by liquid chromatography-mass spectrometry (LC-MS). In the metabolome evaluation, 6209 differential metabolites were screened, including 3394 up-regulated and 2815 down-regulated metabolites. Fifteen metabolic pathways of Y. enterocolitica exhibited significant changes after LA treatment, including the pathways important for amino acid and nucleotide metabolism. The results show that LA is a bacteriostatic substance with potential application value in the food industry.

Health Benefits and Risks of Consuming Spices on the Example of Black Pepper and Cinnamon

The aim of this study is to present the benefits and risks associated with the consumption of black pepper and cinnamon, which are very popular spices in Poland. The article presents the current state of knowledge about health properties and possible dangers, such as liver damage, associated with their consumption. The experimental part presents the results of the research on the antioxidant properties against the DPPH radical, which was 80.85 ± 3.84–85.42 ± 2.34% for black pepper, and 55.52 ± 7.56–91.87 ± 2.93% for cinnamon. The total content of polyphenols in black pepper was 10.67 ± 1.30–32.13 ± 0.24 mg GAE/g, and in cinnamon 52.34 ± 0.96–94.71 ± 3.34 mg GAE/g. In addition, the content of piperine and pepper oil in black pepper was determined, as well as the content of coumarin in cinnamon. The content of piperine in the black pepper samples was in the range of 3.92 ± 0.35–9.23 ± 0.05%. The tested black pepper samples contained 0.89 ± 0.08–2.19 ± 0.15 mL/100 g d.m. of essential oil. The coumarin content in the cinnamon samples remained in the range of 1027.67 ± 50.36–4012.00 ± 79.57 mg/kg. Taking into account the content of coumarin in the tested cinnamon samples, it should be assumed that the majority of cinnamon available in Polish retail is Cinnamomum cassia (L.) J. Presl.

In Vitro Analysis of Extracts of Plant Used in Mexican Traditional Medicine, Which Are Useful to Combat Clostridioides difficile Infection

Recently, a worrying acceleration of the emergence of antibiotic-resistant bacteria has been reported. The increase in antibiotic-associated diseases, such as Clostridioides difficile infection (CDI), has promoted research on new treatments that could be more effective and less aggressive for CDI patients. This study evaluates eight plants with antimicrobial activity commonly used in Mexican traditional medicine to evaluate their potential against C. difficile. We provide essential information about these plants’ activities and action mechanisms against C. difficile and their effect on different bacterial infection activities: motility, adherence, sporulation, and germination. The selected plants are rosemary, estafiate, rue, epazote, mint, toloache, ajenjo, and thyme. We used clinical isolates to test their activity against strains responsible for current outbreaks to provide more information about the clinical impact of these extracts. We found that thyme, ajenjo, and mint were the most effective against the isolates. We identified that the extracts affected protein synthesis. In addition, the extracts affect the strains’ motility, and some, such as thyme extract, affect adherence, whereas rue extract affects sporulation. These results led to the identification of new compounds beneficial to CDI treatment.

Multi-Target Antibacterial Mechanism of Moringin From Moringa oleifera Seeds Against Listeria monocytogenes

Moringin [4-(α-L-rhamnosyloxy) benzyl isothiocyanate] is an isothiocyanate from Moringa oleifera seeds. It is the bioactivated form of the glucosinolate precursor glucomoringin with various health benefits. However, few studies have examined the antibacterial activity of moringin. This study aimed to investigate the antimicrobial activity and mechanism of moringin against Listeria monocytogenes. The minimum inhibitory concentration (MIC), and growth curves were used to evaluate the bacteriostatic effect of moringin against L. monocytogenes. Transcriptome analysis by RNA sequencing was performed to elucidate the underlying mechanism of moringin against L. monocytogenes. The transcriptome results were validated. The results showed that moringin inhibited the growth of L. monocytogenes with a MIC of 400 μM. RNA sequencing results showed that the differences in the expression of genes related to the cell wall and membrane biosynthesis, phosphotransferase system (PTS), oxidative stress, energy metabolism, and DNA binding were significantly affected. As with the transcriptome results, the results of the mechanism verification found that moringin damaged the integrity of the cell wall and cell membrane, stimulated oxidative stress, interfered with energy metabolism and DNA replication, and finally led to the death of L. monocytogenes. The present study provides evidence that moringin exhibits strong antimicrobial activity against L. monocytogenes and insight into its potential mechanism.

In vitro anti-clostridial action and potential of the spice herbs essential oils to prevent biofilm formation of hypervirulent Clostridioides difficile strains isolated from hospitalized patients with CDI

BACKGROUND

Clostridioides difficile is the most common causative agent of antibiotic-acquired diarrhea in hospitalized patients associated with substantial morbidity and mortality. The global epidemic of CDI (Clostridioides difficile infection) began in the early 20th century with the emergence of the hypervirulent and resistant ribotype 027 strains, and requires an urgent search for new therapeutic agents.

OBJECTIVE

The aim of this study is to investigate the antibacterial activity of the three essential oils isolated from spice herbs (wild oregano, garlic and black pepper) against C. difficile clinical isolates belonging to 6 different PCR ribotypes and their potential inhibitory effect on the biofilm production in in vitro conditions.

RESULTS

Wild oregano essential oil showed strong inhibitory activity in concentrations 0.02-1.25 mg/mL and bactericidal activity in concentrations from 0.08 to 10 mg/mL. Garlic essential oil was effective in the concentration range of 0.02-40 mg/mL, and 0.16 - > 40 mg/mL. MIC and MBC for black pepper oil ranged from 0.04 to 40 mg/mL, and 0.08 - > 40 mg/mL, respectively. All the tested oils reduced in vitro biofilm production, with the best activity of oregano oil.

CONCLUSION

Essential oils of wild oregano, black pepper and garlic are candidates for adjunctive therapeutics in the treatment of CDI. Oregano oil should certainly be preferred due to the lack of selectivity of action in relation to the ribotype, the strength of the produced biofilm and/or antibiotic-susceptibility patterns.

Metabolomics Insights into Chemical Convergence in Xanthomonas perforans and Metabolic Changes Following Treatment with the Small Molecule Carvacrol

Microbes are natural chemical factories and their metabolome comprise diverse arrays of chemicals. The genus Xanthomonas comprises some of the most important plant pathogens causing devastating yield losses globally and previous studies suggested that species in the genus are untapped chemical minefields. In this study, we applied an untargeted metabolomics approach to study the metabolome of a globally spread important xanthomonad, X. perforans. The pathogen is difficult to manage, but recent studies suggest that the small molecule carvacrol was efficient in disease control. Bacterial strains were treated with carvacrol, and samples were taken at time intervals (1 and 6 h). An untreated control was also included. There were five replicates for each sample and samples were prepared for metabolomics profiling using the standard procedure. Metabolomics profiling was carried out using a thermo Q-Exactive orbitrap mass spectrometer with Dionex ultra high-performance liquid chromatography (UHPLC) and an autosampler. Annotation of significant metabolites using the Metabolomics Standards Initiative level 2 identified an array of novel metabolites that were previously not reported in Xanthomonas perforans. These metabolites include methoxybrassinin and cyclobrassinone, which are known metabolites of brassicas; sarmentosin, a metabolite of the Passiflora-heliconiine butterfly system; and monatin, a naturally occurring sweetener found in Sclerochiton ilicifolius. To our knowledge, this is the first report of these metabolites in a microbial system. Other significant metabolites previously identified in non-Xanthomonas systems but reported in this study include maculosin; piperidine; β-carboline alkaloids, such as harman and derivatives; and several important medically relevant metabolites, such as valsartan, metharbital, pirbuterol, and ozagrel. This finding is consistent with convergent evolution found in reported biological systems. Analyses of the effect of carvacrol in time-series and associated pathways suggest that carvacrol has a global effect on the metabolome of X. perforans, showing marked changes in metabolites that are critical in energy biosynthesis and degradation pathways, amino acid pathways, nucleic acid pathways, as well as the newly identified metabolites whose pathways are unknown. This study provides the first insight into the X. perforans metabolome and additionally lays a metabolomics-guided foundation for characterization of novel metabolites and pathways in xanthomonad systems.

Insights into the Phytochemical and Multifunctional Biological Profile of Spices from the Genus Piper

Piper spices represent an inexhaustible reservoir of bioactive compounds that may act as drug leads in natural product research. The aim of this study was to investigate a series of methanolic fruit extracts obtained from P. nigrum (black, green, white and red), P. longum and P. retrofractum in comparative phytochemical and multi-directional biological (antimicrobial, antioxidant, anti-enzymatic and anti-melanogenic) assays. The metabolite profiling revealed the presence of 17 piperamides, with a total content of 247.75-591.42 mg piperine equivalents/g. Among the 22 tested microorganism strains, Piper spices were significantly active (MIC < 0.1 mg/mL) against the anaerobes Actinomyces israelii and Fusobacterium nucleatum. The antioxidant and anti-enzymatic activities were evidenced in DPPH (10.64-82.44 mg TE/g) and ABTS (14.20-77.60 mg TE/g) radical scavenging, CUPRAC (39.94-140.52 mg TE/g), FRAP (16.05-77.00 mg TE/g), chelating (0-34.80 mg EDTAE/g), anti-acetylcholinesterase (0-2.27 mg GALAE/g), anti-butyrylcholinesterase (0.60-3.11 mg GALAE/g), anti-amylase (0.62-1.11 mmol ACAE/g) and anti-glucosidase (0-1.22 mmol ACAE/g) assays. Several Piper extracts (10 μg/mL) inhibited both melanin synthesis (to 32.05-60.65% of αMSH+ cells) and release (38.06-45.78% of αMSH+ cells) in αMSH-stimulated B16F10 cells, partly explained by their tyrosinase inhibitory properties. Our study uncovers differences between Piper spices and sheds light on their potential use as nutraceuticals or cosmeceuticals for the management of different diseases linked to bacterial infections, Alzheimer's dementia, type 2 diabetes mellitus or hyperpigmentation.

Phytochemistry and therapeutic potential of black pepper [Piper nigrum (L.)] essential oil and piperine: a review

Background

Black pepper [Piper nigrum (L.), Family: Piperaceae] is used traditionally for the treatment of various diseases including; cough, cold, dyspnea throat diseases, intermittent fever, dysentery, stomachache, worms and piles. The pharmacological potential of black pepper is due to the presence of metabolites like phenolic compounds, alkaloids, flavonoids, carotenoids, terpenoids, etc. The multipurpose use of black pepper dried seeds has several other beneficial health effects that also received in the light of traditional as well as current medicine perspectives. The review aims to discuss the botany, phytochemical constituents, and pharmacological properties of piperine and black pepper essential oil (BPEO).

Results

Phytochemical analyses have described the main chemical constituents of black pepper, including carbohydrates, proteins, calcium, magnesium, potassium, iron, vitamin C, tannins, flavonoids and carotenoids. The volatile oil content ranges from 0.4 to 7 % in dried berries. The major constituents of BPEO are sabinene, 3-carene, D-limonene, α-pinene, caryophyllene, β-phellandrene, α-phellandrene, α-thujene, and β-bisabolene. Additionally, piperine is the naturally occurring and principal bioactive alkaloid constituent of black pepper owing to its potential therapeutic properties, including cerebral brain functioning and increased nutrient absorption. The BPEO has several biological roles, including antioxidant, anti-inflammatory, anticancer, anti-obesity, antidepressant, antidiabetic, antimicrobial, gastroprotective, and insecticidal activities.

Conclusions

This review examines and presents the appropriate evidence on black pepper and its traditional uses as well as biological activities of BPEO and piperine. Although several previous reports showed diverse biological effects for piperine and bioactive constitutes of BPEO. Thus, minimal investigations were conducted using animal models, and many of these studies also lacked appropriate experimental setting like doses, control details. Hence, future studies are necessary to understand the mechanism of piperine, BPEO, bioactive constituents and their effects upon their use by animal models and humans with the proper experimental procedure which we can facilitate the protection of human health from several diseases.

On the mechanism behind enhanced antibacterial activity of alkyl gallate esters against foodborne pathogens and its application in Chinese icefish preservation

The objective of this study was to investigate antibacterial activities and action mode of alkyl gallates against three food-related bacteria. Results show that the length of the alkyl chain plays a critical role in eliciting their antibacterial activities and octyl gallate (GAC8) exhibited an outstanding bactericidal effect against these strains. A possible bactericidal mechanism of GAC8 against E. coli was fully elucidated by analyzing associated changes in cellular functions of E. coli, including assessments of membrane modification and intracellular oxidation state. Our data strongly suggested that GAC8 functions outside and inside the bacterial membrane and causes increased intracellular reactive oxygen species (hydroxyl radicals) and subsequent oxidative damage. We demonstrated that the hydroxyl radical formation induced by GAC8 is the end product of an oxidative damage cellular death pathway involving a transient depletion of NADH, the tricarboxylic acid cycle, intrinsic redox cycling activities, and stimulation of the Fenton reaction. Also, chitosan-based edible films containing GAC8 have unique superiorities for icefish preservation at 4 °C. This research highlights the effectiveness of GAC8 as an attractive antibacterial, which possesses both antioxidant and antibacterial activities and can be used as a multifunctional food additive combined with the benefit of active packaging for food preservations.

Grapefruit Seed Extract as a Natural Derived Antibacterial Substance against Multidrug-Resistant Bacteria

Multidrug-resistant (MDR) bacteria are increasing due to the abuse and misuse of antibiotics, and nosocomial infections by MDR bacteria are also increasing. The aim of this study was to identify new substances that can target MDR bacteria among 12 plant extracts that are known to have antibacterial effects. The experiments were performed by the disk diffusion test and microdilution minimum inhibitory concentration (MIC) test, as described by the Clinical and Laboratory Standards Institute (CLSI). By screening against methicillin-sensitive Staphylococcus aureus (MSSA), grapefruit seed extract (GSE) was selected from 12 plant extracts for subsequent experiments. GSE showed antibacterial effects against methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) in the disk diffusion test. Even at the lowest concentration, GSE showed antibacterial activity in the microdilution MIC test. As a result, we can conclude that GSE is a naturally derived antibacterial substance that exhibits a favorable antibacterial effect even at a very low concentration, so it is a good candidate for a natural substance that can be used to prevent or reduce nosocomial infections as coating for materials used in medical contexts or by mixing a small amount with other materials.

A systematic review on COVID-19 pandemic with special emphasis on curative potentials of Nigeria based medicinal plants

Despite the frightening mortality rate associated with COVID-19, there is no known approved drug to effectively combat the pandemic. COVID-19 clinical manifestations include fever, fatigue, cough, shortness of breath, and other complications. At present, there is no known effective treatment or vaccine that can mitigate/inhibit SARS-CoV-2. Available clinical intervention for COVID-19 is only palliative and limited to support. Thus, there is an exigent need for effective and non-invasive treatment. This article evaluates the possible mechanism of actions of SARS-CoV-2 and present Nigeria based medicinal plants which have pharmacological and biological activities that can mitigate the hallmarks of the pathogenesis of COVID-19. SARS-CoV-2 mode of actions includes hyper-inflammation characterized by a severe and fatal hyper-cytokinaemia with multi-organ failure; immunosuppression; reduction of angiotensin-converting enzyme 2 (ACE2) to enhance pulmonary vascular permeability causing damage to the alveoli; and further activated by open reading frame (ORF)3a, ORF3b, and ORF7a via c-Jun N- terminal kinase (JNK) pathway which induces lung damage. These mechanisms of action of SARS-CoV-2 can be mitigated by a combination therapy of medicinal herbs based on their pharmacological activities. Since the clinical manifestations of COVID-19 are multifactorial with co-morbidities, we strongly recommend the use of combined therapy such that two or more herbs with specific therapeutic actions are administered to combat the mediators of the disease.

Oxidative stress induced by piperine leads to apoptosis in Candida albicans

Candida albicans is a member of pathogens with potential drug resistance threat that needs novel chemotherapeutic strategies. Considering the multifarious biological activities including bioenhancer activity, anti-Candida potential of piperine was evaluated against planktonic/biofilm and hyphal growth of C. albicans alone or in combination as a synergistic agent with fluconazole. Piperine inhibits planktonic growth at or less than 15 μg/ml, hyphae induction at 5 μg/ml concentration, and exhibits stage-dependent activity against biofilm growth of a fluconazole-resistant strain of C. albicans (ATCC10231). Though piperine couldn't kill inoculum completely at minimum inhibitory concentration (MIC), it is fungicidal at higher concentrations, as shown in apoptosis assay. FIC index values indicate that piperine exhibits excellent synergistic activity with fluconazole against planktonic (0.123) and biofilm (0.215) growth of an FLC resistant strain. Mode of anti-Candida activity was studied by identifying piperine responsive proteins wherein the abundance of 25 proteins involved in stress response, signal transduction and cell cycle were modulated (22 up and 3 down-regulated) significantly in response to piperine (MIC50). Modulation of the proteins involved suggests that piperine affects membrane integrity leading to oxidative stress followed by cell cycle arrest and apoptosis in C. albicans. Flow cytometry-based mitochondrial membrane potential (MMP), cell cycle and apoptosis assay, as well as real-time quantitative polymerase chain reaction analysis of selected genes, confirms piperine induced oxidative stress (TRR1), cell cycle arrest and apoptosis (CaMCA1). Based on our results, we conclude that piperine inhibits planktonic and difficult-to treat-biofilm growth of C. albicans by affecting membrane integrity thereby inducing oxidative stress and apoptosis.

LAY ABSTRACT

Piperine inhibit Candida albicans growth (planktonic and biofilm) significantly in our study. Piperine exhibits excellent synergistic potential with fluconazole The proteome analysis suggests that piperine induced membrane damage leads to oxidative stress followed by cell cycle arrest and apoptosis.

Metabolomics study on revealing the inhibition and metabolic dysregulation in Pseudomonas fluorescens induced by 3-carene

3-Carene is a monoterpenoid that has an effective inhibitory ability against Pseudomonas fluorescens (P. fluorescens) which can induce a range of food contamination problems. In this study, ultra-performance liquid chromatography-mass spectrometry (UPLC-MS)-based metabolomics was used to elucidate the antimicrobial mechanism of 3-carene in P. fluorescens. Multivariate analysis of the metabolite data revealed significant differences in the potential metabolite profiles between groups. The results of univariate analysis showed that significant changes in 42 metabolites were observed after treatment with 3-carene for 12 h when compared to the control group. Moreover, 3-carene treatment resulted in disturbances in many metabolic processes, including amino acid metabolism, pantothenate and coenzyme A (CoA) biosynthesis and the tricarboxylic acid (TCA) cycle. These results provide a new insight into the antimicrobial mechanisms of 3-carene in P. fluorescens and enhance our understanding of the antimicrobial mechanism from a metabolic perspective.

Manufacture and antibacterial characteristics of Eucommia ulmoides leaves vinegar

In this work, the fermentation conditions and the antibacterial characteristics of Eucommia ulmoides leaves vinegar (EV) were studied. By single factor orthogonal test, it was found that under optimal fermentation conditions (bran addition 10%, sugar addition 8%, leaven addition 0.3% and acetic acid bacteria solution 12%), the acetic acid content and CA content of EV were 45.5 ± 2.8 mg/mL and 0.98 ± 0.08 mg/mL, respectively. Then, by the disc diffusion method, it was concluded that the antibacterial effect of EV was significantly higher than that of Eucommia ulmoides leaves enzymatic hydrolysate and Zhenjiang aromatic vinegar (P<0.05). An investigation into action mode of EV against Bacillus subtilis indicated that, under the combined action of CA and acetic acid, EV exerted its antibacterial effect by damaging bacterial cell wall and cell membrane, increasing the cell permeability which resulted in the structural lesions and release of cell components, thus led to cell death.

Antibacterial activity and mechanism of linalool against Pseudomonas aeruginosa

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.

Inactivation mechanism of E. coli O157:H7 under ultrasonic sterilization

Ultrasonic sterilization (US), as a promising non-thermal sterilization method, exhibits unique superiorities than traditional sterilization methods. In this study, the inactivation mechanism of E. coli O157:H7 under US was investigated in cucumber and bitter gourd vegetable juices. Results revealed that the US treatment showed good antibacterial ability in countering E. coli O157:H7. Through determinations of conductivity and β-galactosidase activity, significant augmentation in membrane permeability of the bacteria was confirmed after the US treatment. The morphologies of the US treated E. coli O157:H7 demonstrated that the integrity of the cell membrane was disrupted by US treatment. SDS-PAGE and LSCM data further proved the disruptive action of US, leading to the leakage of proteins and DNA through the breakage on cell membrane. The decrease of metabolic-related enzyme activity was verified through investigation of bacterial metabolism. The antibacterial mechanism analysis indicated that the US can generate free radicals which resulted in the rise of intracellular oxidative stress, attenuation of energy metabolism and inhibition of hexose monophosphate pathway. As the application verification, the US treatment can cause the deprivation of E. coli O157:H7 cell viability in vegetable juices without obvious impact on the sensory quality.

Chemical composition, antibacterial activity and related mechanism of valonia and shell from Quercus variabilis Blume (Fagaceae) against Salmonella paratyphi a and Staphylococcus aureus

BACKGROUND

Plant secondary metabolites and phytochemicals that exhibit strong bioactivities have potential to be developed as safe and efficient natural antimicrobials against food contamination and addressing antimicrobial resistance caused by the overuse of chemical synthetic preservative. In this study, the chemical composition, antibacterial activities and related mechanism of the extracts of the valonia and the shell of Quercus variabilis Blume were studied to determine its potential as a safe and efficient natural antimicrobial.

METHODS

The phenolic compositions of valonia and shell extracts were determined by folin-ciocalteau colourimetric method, sodium borohydride/chloranil-based assay and the aluminium chloride method and then further identified by the reverse-phase HPLC analysis. The antibacterial activities of valonia and shell extracts were evaluated by the agar disk diffusion method and agar dilution method. The related antibacterial mechanism was explored successively by the membrane of pathogens effect, phosphorous metabolism, whole-cell proteins and the microbial morphology under scanning electron microscopy.

RESULTS

The n-butanol fraction and water fraction of valonia along with n-butanol fraction of the shell contains enrich phenolics including ellagic acid, theophylline, caffeic acid and tannin acid. The n-butanol fraction and ethanol crude extracts of valonia exhibited strong antibacterial activities against Salmonella paratyphi A (S. paratyphi A) and Staphylococcus aureus (S. aureus) with the DIZ values ranged from 10.89 ± 0.12 to 15.92 ± 0.44, which were greater than that of the Punica granatum (DIZ: 10.22 ± 0.18 and 10.30 ± 0.21). The MIC values of the n-butanol fraction and ethanol crude extracts of valonia against S. paratyphi A and S. aureus were 1.25 mg/ml and 0.625 mg/ml. The related antibacterial mechanism of n-butanol fraction and ethanol crude extracts of valonia may be attributed to their strong impact on membrane permeability and cellular metabolism. Those extracts exhibited strong antibacterial activity according to inhibit the synthesis of bacterial proteins and seriously change morphological structure of bacterial cells.

CONCLUSIONS

The n-butanol fraction and ethanol crude extracts of valonia had reasonably good antibacterial activities against S. paratyphi A and S. aureus. This study suggests possible application of valonia and shell as natural antimicrobials or preservatives for food and medical application.

Antimicrobial activity of flavonoids from Sedum aizoon L. against Aeromonas in culture medium and in frozen pork

The chemical composition and antimicrobial activity of flavonoids from Sedum aizoon L. against Aeromonas in vitro were investigated, and the effect of flavonoid treatment on the quality of fresh pork during frozen storage for 6 months was also explored. The results showed that kaempferol, quercetin dihydrate, and catechin were the most predominant flavonoids from S. aizoon L. Flavonoids exhibited antibacterial activity to Aeromonas in vitro, which caused membrane damage, disruption of the bacterial surface, and internal ultrastructure, and resulted in the leakage of reducing sugars and proteins. Meanwhile, flavonoid treatment retarded the microbial growth and deteriorates of pork characteristics, including pH value, total volatile basic nitrogen (TVB-N), texture, and sensory evaluation during frozen storage, thereby prolonged the shelf life. Their results suggested that flavonoids from S. aizoon L. offer a promising choice for food safety and preservation.

Antimicrobial Activity and Proposed Action Mechanism of 3-Carene against Brochothrix thermosphacta and Pseudomonas fluorescens

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.

Piper Species: A Comprehensive Review on Their Phytochemistry, Biological Activities and Applications

Piper species are aromatic plants used as spices in the kitchen, but their secondary metabolites have also shown biological effects on human health. These plants are rich in essential oils, which can be found in their fruits, seeds, leaves, branches, roots and stems. Some Piper species have simple chemical profiles, while others, such as Piper nigrum, Piper betle, and Piper auritum, contain very diverse suites of secondary metabolites. In traditional medicine, Piper species have been used worldwide to treat several diseases such as urological problems, skin, liver and stomach ailments, for wound healing, and as antipyretic and anti-inflammatory agents. In addition, Piper species could be used as natural antioxidants and antimicrobial agents in food preservation. The phytochemicals and essential oils of Piper species have shown strong antioxidant activity, in comparison with synthetic antioxidants, and demonstrated antibacterial and antifungal activities against human pathogens. Moreover, Piper species possess therapeutic and preventive potential against several chronic disorders. Among the functional properties of Piper plants/extracts/active components the antiproliferative, anti-inflammatory, and neuropharmacological activities of the extracts and extract-derived bioactive constituents are thought to be key effects for the protection against chronic conditions, based on preclinical in vitro and in vivo studies, besides clinical studies. Habitats and cultivation of Piper species are also covered in this review. In this current work, available literature of chemical constituents of the essential oils Piper plants, their use in traditional medicine, their applications as a food preservative, their antiparasitic activities and other important biological activities are reviewed.

Antifungal effects of thymol and salicylic acid on cell membrane and mitochondria of Rhizopus stolonifer and their application in postharvest preservation of tomatoes

This study investigated effects of the simultaneous application of thymol and salicylic acid (SIM_TSA) on the target sites of Rhizopus stolonifer, as well as the defenceenzymes of postharvest tomato, when applied as edible coating. SIM_TSA induced the changes of ultrastructure and membrane integrity of R. stolonifer. When the concentrations of the fungistat increased, cells stained with propidium iodide and leakage of 260/280 nm-absorbing materials increased while ergosterol synthesis decreased, suggesting damage of cell membrane. Furthermore, SIM_TSA treatment significantly reduced the citric acid content and the activities of enzymes related to the tricarboxylic acid cycle, and increased the mitochondrial membrane potential and the reactive oxygen species, indicating damage of mitochondrial-related functions. Moreover, SIM_TSA edible coating increased the defence enzyme activities in tomato. Based on the results, SIM_TSA can be used as a potential preservation method for tomato as it showed a targeted effect on the cell membrane and mitochondria of R. stolonifer.

Antibacterial Effect of Black Pepper Petroleum Ether Extract against Listeria monocytogenes and Salmonella typhimurium

The aim of the present study was to evaluate the antibacterial effect of black pepper petroleum ether extract (BPPE) against Listeria monocytogenes ATCC 19115 and Salmonella typhimurium ATCC 14028. The results showed that the BPPE had a strong antimicrobial activity against L. monocytogenes and S. typhimurium, and 2-methylene-4,8,8-trimethyl-4-vinyl-bicyclo[5.2.0]nonane (9.36%) and caryophyllene oxide (4.85%) were identified as the two primary components of BPPE. The ability of cells to break down hyperoxide was decreased, and the activities of POD and CAT were inhibited. The activities of key metabolic enzymes shed some light on the biochemical mechanism of aglycon cell growth inhibition, indicating that the energetic metabolism of L. monocytogenes and S. typhimurium was markedly influenced by the BPPE. The contents of key organic acids varied significantly, resulting in remarkable abnormalities in the energetic metabolism of L. monocytogenes and S. typhimurium. Thus, the consecution of energetic metabolism was destroyed by the BPPE, which contributed to metabolic dysfunction, the suppression of gene transcription, and cell death.

Pulverizing processes affect the chemical quality and thermal property of black, white, and green pepper (Piper nigrum L.)

In this study, the effects of different pulverizing methods on the chemical attributes and thermal properties of black, white and green pepper were evaluated. Cryogenic grinding minimally damaged the lipid, moisture, crude protein, starch, non-volatile ether extract, piperine, essential oil and the typical pepper essential oil compounds of the spices. The pulverizing methods and storage significantly affected the compositions of the fatty acid in the peppers, except for palmitic acid and lignoceric acid. The amino acid contents and the thermo-gravimetric analysis curve were hardly influenced by the grinding techniques. The use of cryogenic grinding to prepare pepper ensured the highest quality of pepper products. Regardless of grinding technique, the values of moisture, piperine, unsaturated fatty acids, essential oil, monoterpenes, and the absolute concentrations of typical pepper essential oil constituents (except caryophyllene oxide) decreased, whereas the amino acid, lipid, protein, starch, and non-volatile ether extract content as well as the thermal properties were insignificantly changed after storage at 4 °C for 6 months.

Comparative Evaluation of the Antioxidant Capacities, Organic Acids, and Volatiles of Papaya Juices Fermented by Lactobacillus acidophilus and Lactobacillus plantarum

Fermentation of foods by lactic acid bacteria is a useful way to improve the nutritional value of foods. In this study, the health-promoting effects of fermented papaya juices by two species, Lactobacillus acidophilus and Lactobacillus plantarum, were determined. Changes in pH, reducing sugar, organic acids, and volatile compounds were determined, and the vitamin C, total phenolic content, and flavonoid and antioxidant capacities during the fermentation process were investigated. Juices fermented by Lactobacillus acidophilus and Lactobacillus plantarum had similar changes in pH and reducing sugar content during the 48 h fermentation period. Large amounts of aroma-associated compounds and organic acids were produced, especially lactic acid, which increased significantly (p<0.05) (543.18 mg/100 mL and 571.29 mg/100 mL, resp.), improving the quality of the beverage. In contrast, the production of four antioxidant capacities in the fermented papaya juices showed different trends after 48 hours’ fermentation by two bacteria. Lactobacillus plantarum generated better antioxidant activities compared to Lactobacillus acidophilus after 48 h of fermentation. These results indicate that fermentation of papaya juice can improve its utilization and nutritional effect.

Effects of Black Pepper (Piper nigrum L.) Chloroform Extract on the Enzymatic Activity and Metabolism of Escherichia coli and Staphylococcus aureus

The chemical composition and antimicrobial mechanism of action of black pepper chloroform extract (BPCE) were investigated, as well as the potential antibacterial activities of BPCE against Escherichia coli and Staphylococcus aureus. The results showed that 1H-Cycloprop[e]azulen-7-ol, decahydro-1,1,7-trimethyl-4-methylene-, [1ar-(1aα,4aα,7β,7a,β,7bα.)]- (8.39%) and 2-methylene-4,8,8-trimethyl-4-vinyl-bicyclo[5.2.0]nonane (6.92%) were identified as the two primary components of BPCE. The release of intracellular transaminases from bacteria after being incubated with BPCE revealed that the bacterial cell walls and membranes were degraded and that protein synthesis was inhibited to some extent. The inhibition of bacterial Na+/K+-ATPase activity upon the addition of BPCE also indicated an enhanced permeability of bacterial cell membranes. Moreover, an analysis of hexokinase and pyruvate kinase activities showed that BPCE affected the metabolic rate of glycolysis and disrupted the normal metabolism of bacteria. This phenomenon was supported by an observed accumulation of lactic acid (LA) in the treated bacterial cells. Overall, our results indicated that BPCE damaged bacterial cell walls and membranes, which was followed by a disruption of bacterial cell respiration.