Enzyme-assisted extraction of flavanones from citrus pomace: Obtention of natural compounds with anti-virulence and anti-adhesive effect against Salmonella enterica subsp. enterica serovar Typhimurium

Antibacterial effects of cinnamaldehyde and hesperitin on resistant Glaesserella parasuis by suppressing QseBC two-component system

BACKGROUND

Glaesserella parasuis (G. parasuis) is one of the most important porcine pathogens causing Glässer's disease, and QseBC two-component system (TCS) is associated with various behaviors of G. parasuis. Our preliminary tests confirmed that plant-derived compounds cinnamaldehyde (CAL) and hesperitin (HES) exhibited promising antimicrobial activity against G. parasuis. Here, we further investigate the antimicrobial effects of CAL and HES on G. parasuis and the underlying mechanisms.

RESULTS

We observed that CAL and HES affected the morphology and physiology of G. parasuis based on the biofilm biomass, confocal laser scanning microscope (CLSM) assay, scanning electron microscope (SEM) assay, and conductivity determination as well as intracellular iron level measurement either used alone or in combination. Moreover, CAL and HES can inhibit QseBC TCS of G. parasuis by down-regulating the QseBC related genes and quenching the QseC protein based on quantitative reverse transcription polymerase chain reaction (qRT-PCR) and molecular docking and fluorescence quenching assay. In vivo study further evident that CAL and HES exhibited significant antimicrobial and anti-inflammatory activity on G. parasuis-infected mice.

CONCLUSIONS

These findings suggested that CAL and HES can exert antibacterial activity on resistant G. parasuis by targeting QseBC, and they may serve as the promising antimicrobial agents for the treatment of G. parasuis infection.

Quercetin and Silybin Decrease Intracellular Replication of Piscirickettsia salmonis in SHK-1 Cell

Piscirickettsia salmonis is the pathogen that has most affected the Chilean salmon industry for over 30 years. Considering the problems of excessive use of antibiotics, it is necessary to find new strategies to control this pathogen. Antivirulence therapy is an alternative to reduce the virulence of pathogens without affecting their growth. Polyphenolic compounds have been studied for their antiviral capacity. In this study, the capacity of quercetin and silybin to reduce the intracellular replication of P. salmonis in SHK-1 cells was evaluated. For this, three different infection protocols in Salmon Head Kidney-1(SHK-1) cells were used: co-incubation for 24 h, pre-incubation for 24 h prior to infection, and post-incubation for 24 h after infection. In addition, the effect of co-incubation in rainbow trout intestinal epithelial cells (RTgutGC) and the effect on the phagocytic capacity of SHK-1 cells were evaluated. The results obtained showed that quercetin and silybin decreased the intracellular replication of P. salmonis in SHK-1 cells when they were co-incubated for 24 h; however, they did not have the same effect in RTgutGC cells. On the other hand, both compounds decreased the phagocytosis of SHK-1 cells during co-incubation. These results are promising for the study of new treatments against P. salmonis.

Natural anti-adhesive components against pathogenic bacterial adhesion and infection in gastrointestinal tract: case studies of Helicobacter pylori, Salmonella enterica, Clostridium difficile, and diarrheagenic Escherichia coli

Antimicrobial resistance (AMR) poses a global public health concern. Recognizing the critical role of bacterial adhesion in pathogenesis of infection, anti-adhesive therapy emerges as a promising approach to impede initial bacterial attachment, thus preventing pathogenic colonization and infection. Natural anti-adhesive agents derived from food sources are generally safe and have the potential to inhibit the emergence of resistant bacteria. This comprehensive review explored diverse natural dietary components exhibiting anti-adhesive activities against several model enteric pathogens, including Helicobacter pylori, Salmonella enterica, Clostridium difficile, and three key diarrheagenic Escherichia coli (i.e., enterotoxigenic E. coli, enteropathogenic E. coli, and enterohemorrhagic E. coli). Investigating various anti-adhesive products will advance our understanding of current research of the field and inspire further development of these agents as potential nutraceuticals or adjuvants to improve the efficacy of conventional antibiotics.

Integration of covalent organic frameworks and molecularly imprinted polymers for selective extraction of flavonoid naringenin from grapefruit (Citrus × paradisi Macf.) peels

Grapefruit (Citrus × paradisi Macf.) peel, a by-product of the citrus-processing industry, possesses an important economic value due to the richness of bioactive compounds. In this study, boron-linked covalent organic frameworks integrated with molecularly imprinted polymers (CMIPs) were developed via a facile one-pot bulk polymerization approach for the selective extraction of naringenin from grapefruit peel extract. The obtained CMIPs possessed a three-dimensional network structure with uniform pore size distribution, large surface areas (476 m2/g), and high crystallinity. Benefiting from the hybrid functional monomer APTES-MAA, the acylamino group can coordinate with the boronate ligands of the boroxine-based framework to form B-N bands, facilitating the integration of imprinted cavities with the aromatic skeleton. The composite materials exhibited a high adsorption capacity of 153.65 mg/g, and a short adsorption equilibrium time of 30 min for naringenin, together with favorable selectivity towards other flavonoid analogues. Additionally, the CMIPs captured the template molecules through π-π* interaction and hydrogen bonding, as verified by FT-IR and XPS. Furthermore, they had good performance when employed to enrich naringenin in grapefruit peels extract compared with the common adsorbent materials including AB-8, D101, cationic exchange resin, and active carbon. This research highlights the potential of CMIPs composite materials as a promising alternative adsorbent for naringenin extraction from grapefruit peel.

Antioxidative and Cytoprotective Efficacy of Ethanolic Extracted Cranberry Pomace against Salmonella Enteritidis Infection in Chicken Liver Cells

Salmonella enterica serovar Enteritidis is a globally significant zoonotic foodborne pathogen. Chicken liver is a vital organ that has been recently implicated in several reported human salmonellosis outbreaks in the U.S. One promising strategy for reducing Salmonella in chickens could be through supplementation with natural antimicrobial additives. Ethanolic extracted cranberry pomace (CPOH) is an excellent source of bioactive polyphenolic compounds with antioxidant and antimicrobial activities. However, the protective effect of CPOH against S. Enteritidis-induced chicken hepatic cell damage remains unclear. In this study, we used a chicken hepatoma cell (LMH) infection model to investigate the protective effects and potential mechanisms of CPOH. CPOH increased the viability of S. Enteritidis-infected LMH cells. Furthermore, CPOH reduced the adhesion and invasion of S. Enteritidis to LMH cells. CPOH downregulated the expression of Rho GTPase genes that are essential for Salmonella's entry into LMH cells. Additionally, the expression of antioxidant regulatory genes, such as Nrf2, HO-1, Txn, and Gclc, was increased. Our data show that CPOH effectively protected LMH cells from cell damage through the inhibition of S. Enteritidis adhesion and invasion, as well as the induction of the expression of master antioxidant genes. These findings offer opportunities to develop sustainable, safe, and economic strategies to reduce the colonization and pathogenesis of Salmonella.

Phytochemicals Derived from Agricultural Residues and Their Valuable Properties and Applications

Billions of tons of agro-industrial residues are produced worldwide. This is associated with the risk of pollution as well as management and economic problems. Simultaneously, non-edible portions of many crops are rich in bioactive compounds with valuable properties. For this reason, developing various methods for utilizing agro-industrial residues as a source of high-value by-products is very important. The main objective of the paper is a review of the newest studies on biologically active compounds included in non-edible parts of crops with the highest amount of waste generated annually in the world. The review also provides the newest data on the chemical and biological properties, as well as the potential application of phytochemicals from such waste. The review shows that, in 2020, there were above 6 billion tonnes of residues only from the most popular crops. The greatest amount is generated during sugar, oil, and flour production. All described residues contain valuable phytochemicals that exhibit antioxidant, antimicrobial and very often anti-cancer activity. Many studies show interesting applications, mainly in pharmaceuticals and food production, but also in agriculture and wastewater remediation, as well as metal and steel industries.

The recovery from agro-industrial wastes provides different profiles of anti-inflammatory polyphenols for tailored applications

Food and agro-industrial processing produce a great amount of side-stream and waste materials that are excellent sources of functional bioactive molecules such as phenolic compounds that recover them can be beneficial not only for food sustainability but also to human for many industrial applications such as flavor compounds and therapeutic applications such as antimicrobial and anti-inflammatory. The treatments and extraction techniques have major effects on the recovery of bioactive compounds. Along with the conventional extraction methods, numerous innovative techniques have been evolved and have been optimized to facilitate bioactive extraction more efficiently and sustainably. In this work, we have summarized the state-of-the-art technological approaches concerning novel extraction methods applied for five most produced crops in Italy; Grape Pomace (GP), Tomato Pomace (TP), Olive Pomace (OP), Citrus Pomace (CP), and Spent Coffee Grounds (SCG), presenting the extraction yield and the main class of phenolic classes, with the focus on their biological activity as an anti-inflammatory in vitro and in vivo studies via describing their molecular mechanism of action.

Two-stage nicking enzyme signal amplification (NESA)-based biosensing platform for the ultrasensitive electrochemical detection of pathogenic bacteria

The sensitive and selective detection of pathogenic bacteria represents an essential approach in food safety analysis and clinical diagnostics. We report the development of a simple, rapid, and low-cost electrochemical biosensing strategy for the detection of pathogenic bacteria with ultrasensitivity and high specificity. The biosensor relies on the target and aptamer binding-triggered two-stage nicking enzyme signal amplification (NESA) and three-way junction probe-mediated electrochemical signal transduction. In the presence of the target S. typhimurium, the specific binding of S. typhimurium and aptamer results in the release of a primer, which hybridizes with HAP1 and initiates an extension reaction with the aid of polymerase and dNTPs. A specific recognition site for Nt.BsmaI is generated in the DNA duplex; thus, the produced DNA is nicked and the secondary primer is released (named recycle I). Subsequently, the reaction solution supplemented with a helper DNA is dropped on the electrode surface, and a three-way junction probe containing a specific recognition site for Nt.BsmaI is thus formed. The MB-labeled probe is nicked with the help of Nt.BsmaI and the dissociated primer-helper DNA duplex combines with another HAP2 (named recycle II). Thus, a remarkably decreased electrochemical signal is generated because the electroactive MB is far away from the electrode surface. As far as we know, this work is the first time that NESA and three-way junction probe-mediated electrochemical signal transduction has been used for pathogenic bacteria detection. Under optimal conditions, the results reveal that the calibration plot obtained for S. typhimurium is approximately linear from 9.6 to 9.6 × 10⁵ cfu mL^-1 with the limit of detection of 8 cfu mL^-1. Additionally, the proposed strategy has been successfully applied to the quantitative assay of S. typhimurium in the real samples. Therefore, the NESA-based biosensing strategy might create a useful and practical platform for pathogenic bacteria identification, and the related food safety analysis and clinical diagnosis.

In Vitro Effect of Copper (I) Complex [Cu(NN1)2](ClO4) on Vibrio harveyi BB170 Biofilm Formation

Biofilm formation in pathogenic bacteria is an important factor of resistance to antimicrobial treatments, allowing them to survive for a long time in their hosts. In the search for new antibiofilm agents, in this work we report the activity of a copper (I) complex, [Cu(NN₁)₂]ClO₄, synthesized with Cu (I) and NN1, an imine ligand 6-((quinolin-2-ylmethylene)amino)-2H-chromen-2-one, a derivate of natural compound coumarin. The antibacterial and antibiofilm capacity was evaluated in Vibrio harveyi BB170 used as model bacteria. Antibacterial activity was measured in vitro by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and half-maximal inhibitory concentration (IC₅₀) determination. Antibiofilm capacity of copper (I) complex was analyzed by different concentrations of IC₅₀ values. The results showed that the sub-IC₅₀ concentration, 12.6 µg/mL of the copper (I) complex, was able to reduce biofilm formation by more than 75%, and bacterial viability was reduced by 50%. Inverted and confocal laser scanning microscopy showed that the [Cu(NN₁)₂]ClO₄ complex affected the biofilm structure. Therefore, the copper (I) complex is effective as an antibiofilm compound in V. harveyi BB170.

Citrus processing by-products: an overlooked repository of bioactive compounds

Citrus fruits contain plethora of bioactive compounds stored in edible as well as inedible part. Since, citrus fruits are processed mainly for juice, the residues are disposed in wastelands, hence, plenty of nutritional potential goes in vain. But if utilized wisely, the bioactive phytochemicals in citrus by-products have the ability to revolutionize the functional food industry. In the present review, the composition of citrus by-products in terms of bioactive components and their health benefits has been reviewed. Various extraction techniques used to extract these bioactives has been discussed and a brief overview of purification and utilization of the extracted compounds, in food and nutraceutical industry is also presented. Bioactives in citrus by-products are higher than the peeled fruit, which can be extracted, isolated and incorporated into food systems for development of health foods. From the studies reviewed, it was observed that research reported on utilization of citrus by-products is limited to mainly research labs; proper scale-up process and its adequate research commercialization is the need of hour to transform these bioactives into economical functional ingredients.