In vitro antibacterial and early stage biofilm inhibitory potential of an edible chitosan and its phenolic conjugates against Pseudomonas aeruginosa and Listeria monocytogenes.

In the present study, the antibacterial potential of chitosan grafted with phenolics (CPCs) such as caffeic acid (CCA), ferulic (CFA), and sinapic acid (CSA) were evaluated against foodborne pathogens like Pseudomonas aeruginosa (PA) and Listeria monocytogenes (LM). The geometric means of minimum inhibitory concentration (MIC range 0.05-0.33 mg/ml), bactericidal concentration (MBC range 0.30-0.45 mg/ml), biofilm inhibitory concentration (BIC range 0.42-0.83 mg/ml), and biofilm eradication concentration (BEC range 1.71-3.70 mg/ml) of CPCs were found to be lower than the MIC (0.12-1.08 mg/ml), MBC (0.17-1.84 mg/ml), BIC (4.0-4.50 mg/ml), and BEC (17.4-23.0 mg/ml) of unmodified chitosan against PA and LM. CPCs attenuated the biofilms of PA and LM by increasing the membrane permeability of bacteria embedded within the biofilms. Further, sub MIC of CPCs (0.5 × MIC) significantly reduced the biofilm adhesion (p < 0.001) by representative strains of LM (CCA: 72.2 ± 3.5, CFA: 79.3 ± 0.9, and CSA: 74.9 ± 1.5%) and PA (CCA: 64 ± 1.1, CFA: 67.8 ± 0.8, and CSA: 65.7 ± 4.9%). These results suggested the antibacterial and anti-biofilm potential of CPCs that can be exploited to control foodborne pathogenic infections.

Application of freeze-thaw enzyme impregnation to produce softened root vegetable foods for elderly consumers.

The aims of this study were to determine the viability of using freeze-thaw infusion (FI) technology to produce a range of root vegetables using enzyme treatments with improved texture characteristics for elderly consumers with swallowing difficulties. We applied enzyme impregnation as a technology to soften the textures of root vegetables commonly consumed in Korea; balloon flower root (Platycodon grandiflorus), burdock root (Arctium lappa L.), carrot (Daucus carota L.), and lotus root (Nelumbo nucifera Gaertn) through the use of a texture analyzer after the FI of a commercial enzyme. Out of 15 commercial enzymes that were analyzed, three enzymes exhibited a marked softening effect on the tested carrots, burdock roots, balloon flower roots, and lotus roots. The hardness of the enzymes-treated food materials reached 1.4 × 104 N/m2 for carrots, 3.0 × 104 N/m2 for burdock roots, of 3.0 × 104 N/m2 for balloon flower roots, and 3.2 × 104 N/m2 for lotus roots without changing the original shapes of the samples. These findings confirmed the potential benefits of softening carrots, lotus roots burdock roots, and balloon flower roots and will contribute to the development of foods that can be easily eaten as part of a balanced diet by elderly adults with eating difficulties.

In Vitro Antibacterial Activity of Phlorotannins from Edible Brown Algae, Eisenia bicyclis Against Streptomycin-Resistant Listeria monocytogenes.

Listeria monocytogenes (LM) is an important food borne pathogen responsible for listeriosis. Further, LM is an etiological agent associated with life threatening conditions like meningitis and encephalitis. Biofilm forming and drug resistant LM may potentially become difficult to treat infections and hence effective controlling measures are required to prevent LM infections. In view of this, the present study evaluated an anti-listerial potential of edible brown seaweed, Eisenia bicyclis, by disc diffusion and micro-dilution methods. The results of the present study suggested that the anti-listerial activity of various phlorotannins isolated form E. bicyclis were in the range of 16-256 µg/ml. Among the phlorotannins isolated, fucofuroeckol-A (FAA) exhibited the highest anti-listerial potential (MIC range 16-32 µg/ml) against LM strains tested. Further, in checker board synergy assays, FFA-streptomycin combination exhibited significant synergy (fractional inhibitory concentration index, ∑FIC < 0.5) against aminoglycoside resistant clinical strains of LM. The results of the present study suggested the potential use of edible seaweed E. bicyclis as a source of natural phlorotannins to control food borne pathogenic infections.

Synergistic Antibacterial Effects of Chitosan-Caffeic Acid Conjugate against Antibiotic-Resistant Acne-Related Bacteria.

The object of this study was to discover an alternative therapeutic agent with fewer side effects against acne vulgaris, one of the most common skin diseases. Acne vulgaris is often associated with acne-related bacteria such as Propionibacteriumacnes, Staphylococcusepidermidis, Staphylococcusaureus, and Pseudomonasaeruginosa. Some of these bacteria exhibit a resistance against commercial antibiotics that have been used in the treatment of acne vulgaris (tetracycline, erythromycin, and lincomycin). In the current study, we tested in vitro antibacterial effect of chitosan-phytochemical conjugates on acne-related bacteria. Three chitosan-phytochemical conjugates used in this study exhibited stronger antibacterial activity than that of chitosan (unmodified control). Chitosan-caffeic acid conjugate (CCA) showed the highest antibacterial effect on acne-related bacteria along with minimum inhibitory concentration (MIC; 8 to 256 µg/mL). Additionally, the MIC values of antibiotics against antibiotic-resistant P. acnes and P.aeruginosa strains were dramatically reduced in combination with CCA, suggesting that CCA would restore the antibacterial activity of the antibiotics. The analysis of fractional inhibitory concentration (FIC) indices clearly revealed a synergistic antibacterial effect of CCA with antibiotics. Thus, the median sum of FIC (∑FIC) values against the antibiotic-resistant bacterial strains ranged from 0.375 to 0.533 in the combination mode of CCA and antibiotics. The results of the present study suggested a potential possibility of chitosan-phytochemical conjugates in the control of infections related to acne vulgaris.

Oligochitosan as a potential anti-acne vulgaris agent: combined antibacterial effects against Propionibacterium acnes.

To develop an antibacterial treatment for acne vulgaris using natural substance with few side effects, we investigated the antibacterial activities of oligochitosan against acne-related bacteria, particularly Propionibacterium acnes. Oligochitosan showed potent antibacterial effect on P. acnes. Especially, 10 kDa oligochitosan presented the highest antimicrobial effect with minimum inhibitory concentration values of 32-64 µg/mL on P. acnes. In addition, oligochitosan clearly reversed the antibacterial effect of tetracycline and erythromycin on P. acnes in the combination mode. The combination of tetracycline- or erythromycine-10 kDa oligochitosan resulted in a median ΣFIC range of 0.02-0.56, suggesting that the antibiotics-oligochitosan combination resulted in an antibacterial synergy against P. acnes. Thus, the results obtained in this research strongly supported that erythromycin and tetracycline will restore the antibacterial activity against P. acnes in the combination mode with 10 kDa oligochitosan.

Correction: The anti-inflammatory effect of a glycosylation product derived from the high hydrostatic pressure enzymatic hydrolysate of a flatfish byproduct.

Correction for 'The anti-inflammatory effect of a glycosylation product derived from the high hydrostatic pressure enzymatic hydrolysate of a flatfish byproduct' by In-Hu Choe, et al., Food Funct., 2016, 7, 2557-2565.

The anti-inflammatory effect of a glycosylation product derived from the high hydrostatic pressure enzymatic hydrolysate of a flatfish byproduct.

In this study, flatfish byproducts were hydrolyzed by Protamex at high hydrostatic pressure and glycosylated with ribose to utilize the protein of flatfish byproducts as a nutraceutical. We investigated the anti-inflammatory effects of glycosylated fish byproduct protein hydrolysate (GFPH) and its anti-inflammatory mechanisms were elucidated in lipopolysaccharide (LPS)-stimulated RAW 264.7 mouse macrophage. The results showed that GFPH suppresses LPS-induced production of nitric oxide (NO) and prostaglandin E2 (PGE2) and expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) dose-dependently. The enzyme-linked immunosorbent assay (ELISA) kit clearly demonstrated that GFPH significantly reduced the production of pro-inflammatory cytokines such as, interleukin (IL)-6, interleukin (IL)-1ß and tumor necrosis factor (TNF)-α, and monocyte chemoattractant protein (MCP)-1. Moreover, GFPH reduced nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) activation. These results indicate that the inhibitory effects of GFPH on LPS-induced NO and PGE2 production might be due to the suppression of the NF-κB and MAPKs signaling pathways. Therefore, these results suggest that flatfish byproducts are latent bioactive resources and GFPH may have potential as a therapeutic agent in the treatment of various inflammatory diseases.

Studies on antimicrobial activity of Poncirus trifoliata ethyl extract fraction against methicillin-resistant Staphylococcus aureus and to elucidate its antibacterial mechanism.

Traditional medicinal plants contain a wide variety of chemicals that have potent antibacterial activity. To find an alternative agent of overcoming the problems of methicillin-resistant Staphylococcus aureus (MRSA), the antibacterial mechanism of Ponciruss trifoliata against MRSA was investigated. Ethyl acetate (EtOAc)-soluble extract of P. trifoliata methanolic extract was evaluated for antibacterial activity using minimum inhibitory concentration (MIC). An EtOAc sub-fraction 08 (EA08) from silica-gel open column chromatography exhibited strong anti-MRSA activity. Apart from the study to isolate single compound from EA08, a synergistic antibacterial effect between the sub-fraction and ß-lactam antibiotics against MRSA was determined. In order to elucidate the antibacterial restoring mechanism of EA08 on MRSA, mRNA expression of mecA gene and production penicillin-binding protein 2a (PBP2a) encoded by mecA gene were monitored. EA 08 showed the strongest antibacterial activity with MIC value of 256 µg ml(-1). MIC of oxacillin against MRSA was dramatically reduced from 512 to 16 µg ml(-1) in combination with 256 µg ml(-1) of EA08. The fractional inhibitory concentration index of oxacillin was measured at 0.53 in combination with EA08 against MRSA, suggesting that EA08-oxacillin combinations exert synergetic effect against MRSA. The analysis of RT-PCR and Western blotting profiles revealed that EA08 inhibited mRNA expression of mecA gene and production PBP2a, which is a key determinant for ß-lactam antibiotic resistance, in a dose-dependent manner. These results indicated that EA08 eventually led to the reduction or inhibition of PBP2a production through translational inhibition in MRSA.

Synergistic Antibacterial Effect and Antibacterial Action Mode of Chitosan-Ferulic Acid Conjugate against Methicillin-Resistant Staphylococcus aureus.

We evaluated the synergistic antibacterial effect in combination with the chitosan-ferulic acid conjugate (CFA) and ß-lactam antibiotics, such as ampicillin, penicillin, and oxacillin, against methicillin-resistant Staphylococcus aureus (MRSA) using fractional inhibitory concentration (FIC) indices. CFA clearly reversed the antibacterial activity of ampicillin, penicillin, and oxacillin against MRSA in the combination mode. Among these antibiotics, the combination of oxacillin-CFA resulted in a ∑FICmin range of 0.250 and ∑FICmax of 0.563, suggesting that the oxacillin-CFA combination resulted in an antibacterial synergy effect against MRSA. In addition, we determined that CFA inhibited the mRNA expression of gene mecA and the production of PBP2a, which is a key determinant for ß-lactam antibiotic resistance, in a dosedependent manner. Thus, the results obtained in this study supported the idea on the antibacterial action mechanism that oxacillin will restore the antibacterial activity against MRSA through the suppression of PBP2a production by CFA.

Texture Softening of Beef and Chicken by Enzyme Injection Process.

This research focuses on a new softening technology for use with chicken breast and eye of round beef in order to assist elderly individuals who have difficulty with eating due to changes in their ability to chew (masticatory function) or swallow. We investigated the hardness of chicken breast and eye of round beef through use of a texture analyzer after injection of a commercial enzyme. Among 7 commercial enzymes, bromelain and collupulin exhibited a marked softening effect on the tested chicken breast and eye of round beef given a 1.00% enzyme concentration. The hardness of bromelain-treated chicken breast reached 1.4×10(4) N/m(2), of collupulin-treated chicken breast reached 3.0×10(4) N/m(2), and of bromelain-treated eye of round beef reached 3.2×10(4) N/m(2), respectively, while their original shapes did not change. To find the level of tissue degradation with specific enzyme concentrations, enzyme injections at 0.1%, 0.25%, 0.50%, and 1.00% concentration of bromelain and papain were also evaluated. The results of this research could be useful for softening chicken breast and eye of round beef and will contribute to the development of foods that can be more easily eaten as part of a balanced diet for elderly adults.

The mechanism of antibacterial activity of phlorofucofuroeckol-A against methicillin-resistant Staphylococcus aureus.

To find more effective ways of overcoming methicillin-resistant Staphylococcus aureus (MRSA), there has been considerable interest in the use of marine-derived constituents as alternatives to control pathogenic microorganisms. In this study, we investigated whether phlorofucofuroeckol-A (PFF) isolated from the edible brown alga Eisenia bicyclis suppressed production or function of penicillin-binding protein 2a (PBP2a). The antimicrobial mode of action of PFF in MRSA was identified by measuring cell membrane integrity and using the time-kill curve method. We attempted to determine the antimicrobial effects of PFF on the expression level of the resistance determinants mecA and its regulatory genes mecI and mecR1 in MRSA by reverse transcriptase polymerase chain reaction. PFF suppressed mecI, mecR1, and mecA gene expression in a dose-dependent manner. In addition, we revealed PFF mediates the suppressive effect of PBP2a expression in MRSA by Western blot analysis. PFF suppressed production of the PBP2a protein, suggesting that PFF probably acts by controlling the methicillin resistance-associated genes involved in the cell wall and production of PBP2a. These results demonstrate that PFF isolated from E. bicyclis significantly suppressed the expression of the methicillin resistance-associated genes and production of PBP2a, which is considered the primary cause of methicillin resistance.

Antibacterial and synergic effects of gallic acid-grafted-chitosan with ß-lactams against methicillin-resistant Staphylococcus aureus (MRSA).

Methicillin-resistant Staphylococcus aureus (MRSA) is spreading worldwide, emphasizing the need to search for new antibiotics. The anti-MRSA activities of gallic acid-grafted-chitosans (GA-g-chitosans) were investigated against 2 MRSA standards and 10 MRSA clinical isolates by determining the minimum inhibitory concentrations (MICs). GA-g-chitosan (I), which has the highest gallic acid content, exhibited the strongest anti-MRSA activities, with MICs of 32-64 µg/mL. A time-kill investigation revealed that GA-g-chitosan (I) exhibited a bactericidal effect at twice the MIC, also demonstrating good thermal and pH stability. Investigation of cell envelope integrity showed the release of intracellular components with an increasing absorbance value at 260 nm, indicating cell envelope damage caused by the GA-g-chitosan (I), which was further confirmed by transmission electron microscopy. When GA-g-chitosans were combined with ß-lactams, including ampicillin and penicillin, synergistic effects were observed on the 2 standard MRSA strains and on the 10 clinical isolates, with fractional inhibitory indices ranging from 0.125 to 0.625. In the time-kill dynamic confirmation test, synergistic bactericidal effects were observed for the combinations of GA-g-chitosans with ß-lactams, and over 4.0 log CFU/mL reductions were observed after 24 h when combination treatment was used. These results may prove GA-g-chitosans to be a potent agent when combined with ampicillin and penicillin for the elimination of MRSA.

Potential α-glucosidase inhibitors from thermal transformation of (+)-catechin.

Thermal transformation of the (+)-catechin (1) with heating processing afforded a new oxidation product, gambiriin D (2), along with catechin [6'-8]-catechin (3), and (+)-epicatechin (4). The structure of a new catechin dimer with C-C linkage was determined on the basis of spectroscopic data interpretation. The catechin dimers 2 and 3 exhibited significantly improved inhibitory activities against α-glucosidase, with IC50 values of 0.16±0.2 and 0.14±0.2µM, respectively, when compared to parent (+)-catechin. Kinetic analysis showed that the two effective compounds 2 and 3 have noncompetitive modes of action.

Pancreatic lipase inhibitory stilbenoids from the roots of Vitis vinifera.

Bioassay-guided isolation of an aqueous methanolic extract of Vitis vinifera using pancreatic lipase inhibitory activity led to isolation of seven stilbenoids, wilsonol C (1), heyneanol A (2), ampelopsin A (3), pallidol A (4), cis-piceid (5), trans-piceid (6) and trans-resveratrol (7). The structures were established on the basis of NMR and MS spectroscopic data interpretation. All isolates were evaluated for their inhibitory effects on pancreatic lipase, and stilbenoid 1 exhibited potent inhibitory effect on pancreatic lipase with IC50 values of 6.7 ± 0.7 µM.

Marine bacteria: potential sources for compounds to overcome antibiotic resistance.

Methicillin-resistant Staphylococcus aureus (MRSA) is the most problematic Gram-positive bacterium in the context of public health due to its resistance against almost all available antibiotics except vancomycin and teicoplanin. Moreover, glycopeptide-resistant S. aureus have been emerging with the increasing use of glycopeptides. Recently, resistant strains against linezolid and daptomycin, which are alternative drugs to treat MRSA infection, have also been reported. Thus, the development of new drugs or alternative therapies is clearly a matter of urgency. In response to the antibiotic resistance, many researchers have studied for alternative antibiotics and therapies. In this review, anti-MRSA substances isolated from marine bacteria, with their potential antibacterial effect against MRSA as potential anti-MRSA agents, are discussed and several strategies for overcoming the antibiotic resistance are also introduced. Our objective was to highlight marine bacteria that have potential to lead in developing novel antibiotics or clinically useful alternative therapeutic treatments.

Application of yeast Candida utilis to ferment Eisenia bicyclis for enhanced antibacterial effect.

In this study, fermentation broth of Eisenia bicyclis with Candia utilis YM-1 exhibited enhanced antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) and food-borne pathogenic bacteria. To perform a more detailed investigation on the antibacterial activity, the fermented broth of E. bicyclis was extracted with methanol and further fractionated with organic solvents. After 1-day fermentation, the ethyl acetate (EtOAc)-soluble extract exhibited the highest anti-MRSA activity with minimum inhibitory concentration values ranging from 128 to 512 µg/mL, suggesting that the fermentation of E. bicyclis with C. utilis YM-1 may enhance antibacterial activity against MRSA. This effect was correlated to the result obtained by an increase in total phenolic contents in EtOAc-soluble extract. In addition, high-performance liquid chromatography analysis revealed that eckol, dieckol, dioxinodehydroeckol, and phlorofucofuroeckol-A contents in the EtOAc-soluble extract increased significantly. Thus, these results show that anti-MRSA activity of E. bicyclis fermented with C. utilis most likely originated from phlorotannins and allow the possible application of a variety of seaweed functional foods.

Protective effect of phlorotannins from Eisenia bicyclis against lipopolysaccharide-stimulated inflammation in HepG2 cells.

In this study, four bioactive phloroglucinol derivates including phloroglucinol (1), eckol (2), dioxinodehydroeckol (3), and dieckol (4) were isolated from Eisenia bicyclis and characterized by nuclear magnetic resonance (NMR) spectroscopic methods. Moreover, the anti-inflammatory activity of these compounds was investigated on human hepatoma cell line HepG2 cells stimulated by lipopolysaccharide (LPS). It was demonstrated that LPS can induce the production of pro-inflammatory cytokines such as interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) as well as the expression of inflammatory mediators as cyclooxygenase-2 (COX-2), and inducible nitric oxide synthases (iNOS) from HepG2 cells. Among isolated compounds, compound (1) exhibited significant inhibition on LPS-stimulated inflammatory responses in HepG2 cells without any cytotoxicity. Herein, compound (1) suppresses the production of pro-inflammatory cytokines such as IL-1ß, IL-6, and TNF-α and the expression of COX-2 and iNOS. Thus, these results indicated that phlorotannins isolated from E. bicyclis, especially compound (1), can be used as a beneficial source for preventing and treating inflammation response.

Anti-methicillin-resistant Staphylococcus aureus (MRSA) substance from the marine bacterium Pseudomonas sp. UJ-6.

A multivalent approach to discover a novel antibiotic substance against methicillin-resistant Staphylococcus aureus (MRSA), a marine bacterium, UJ-6, exhibiting an antibacterial activity against MRSA was isolated from seawater. The isolated strain was identified to be Pseudomonas sp. by the morphology, biochemical, and genetical analyses. The ethyl acetate extract of Pseudomonas sp. UJ-6 culture showed significant ant-MRSA activity. Bioassay-guided isolation of the extract using a growth inhibitory assay led to the isolation and identification of an active compound exhibiting anti-MRSA activity. Based on the analyses of the physicochemical and spectroscopic data including nuclear magnetic resonance and mass, the compound was identified to be 1-acetyl-beta-carboline. The minimum inhibitory concentration (MIC) of the compound was determined to be in a range of 32-128 µg/ml against MRSA strains. The MIC values against MRSA were superior or equal to those of other natural compounds such as catechins, suggesting that 1-acetyl-beta-carboline would be a good candidate in applications of the treatment of MRSA infection.

Pancreatic lipase inhibitory activity of phlorotannins isolated from Eisenia bicyclis.

Pancreatic lipase is a potential therapeutic target for the treatment of diet-induced obesity in humans. In an ongoing search for new pancreatic lipase inhibitors from natural sources, a methanolic extract of marine brown algae, Eisenia bicyclis, showed a significant inhibitory effect against pancreatic lipase. Bioassay-guided isolation of this methanolic extract using a pancreatic lipase inhibitory assay led to the isolation and identification of six known phlorotannins: eckol (1), fucofuroeckol A (2), 7-phloroeckol (3), dioxindehydroeckol (4), phlorofucofuroeckol A (5), and dieckol (6). The structures were established on the basis of nuclear magnetic resonance and mass spectrometry spectroscopic data interpretation. Among the isolated phloroglucinol polymers, compounds 2 and 3 showed potent inhibitory effects on pancreatic lipase with IC50 values ranging from 37.2 ± 2.3 to 12.7 ± 1.0 µM, respectively.

In vitro antibacterial activity and synergistic antibiotic effects of phlorotannins isolated from Eisenia bicyclis against methicillin-resistant Staphylococcus aureus.

Six phlorotannins, isolated from Eisenia bicyclis, were evaluated for antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MIC) of the compounds were in the range 32 to 64 µg/mL. Phlorofucofuroeckol-A (PFF) exhibited the highest anti-MRSA activity, with an MIC of 32 µg/mL. An investigation of the interaction between these compounds and the ß-lactam antibiotics ampicillin, penicillin, and oxacillin revealed synergistic action against MRSA in combination with compound PFF. To our knowledge, this is the first report on the anti-MRSA activity of phlorotannins from E. bicyclis. The results obtained in this study suggest that the compounds derived from E. bicyclis can be a good source of natural antibacterial agents against MRSA.