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Curcumin, a natural polyphenolic flavonoid extracted from the rhizome of Curcuma longa L., was shown to possess superior potency to resensitize methicillin-resistant Staphylococcus aureus (MRSA) to antibiotics. Previous studies have shown the synergistic activity of curcumin with β-lactam and quinolone antibiotics. Further, to understand the anti-MRSA mechanism of curcumin, we investigated the potentiated effect of curcumin by its interaction in diverse conditions. The mechanism of anti-MRSA action of curcumin was analyzed by the viability assay in the presence of detergents, ATPase inhibitors and peptidoglycan (PGN) from S. aureus, and the PBP2a protein level was analyzed by western blotting. The morphological changes in the curcumin-treated MRSA strains were investigated by transmission electron microscopy (TEM). We analyzed increased susceptibility to MRSA isolates in the presence of curcumin. The optical densities at 600 nm (OD600) of the suspensions treated with the combinations of curcumin with triton X-100 and Tris were reduced to 63% and 59%, respectively, compared to curcumin OPEN ACCESSMolecules 2014, 19 18284 without treatment. N,N'-dicyclohexylcarbodiimide (DCCD) and sodium azide (NaN3) were reduced to 94% and 55%, respectively. When peptidoglycan (PGN) from S. aureus was combined with curcumin, PGN (0-125 μg/mL) gradually blocked the antibacterial activity of curcumin (125 μg/mL); however, at a concentration of 125 µg/mL PGN, it did not completely block curcumin. Curcumin has a significant effect on the protein level of PBP2a. The TEM images of MRSA showed damage of the cell wall, disruption of the cytoplasmic contents, broken cell membrane and cell lysis after the treatment of curcumin. These data indicate a remarkable antibacterial effect of curcumin, with membrane permeability enhancers and ATPase inhibitors, and curcumin did not directly bind to PGN on the cell wall. Further, the antimicrobial action of curcumin involved in the PBP2a-mediated resistance mechanism was investigated.

Luteolin (3′,4′,5,7-tetrahydroxylflavone) is a plant flavonoid and pharmacologically active agent that has been isolated from several plant species. In the present study, the effect of luteolin from the flowers of Lonicera japonica on phorbol 12-myristate 13-acetate (PMA) plus A23187-induced mast cell activation was examined. Luteolin significantly inhibited the induction of inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-8, IL-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF) by PMA plus A23187. Moreover, luteolin attenuated cyclooxygenase (COX)-2 expression and intracellular Ca2+ levels. In activated HMC-1 cells, the phosphorylation of extra-signal response kinase (ERK 1/2) and c-jun N-terminal Kinase (JNK 1/2), but not p38 mitogen-activated protein kinase (p38 MAPK) were decreased by treatment of the cells with luteolin. Luteolin inhibited PMA plus A23187-induced nuclear factor (NF)-κB activation, IκB degradation, and luciferase activity. Furthermore, luteolin suppressed the expression of TNF-α, IL-8, IL-6, GM-CSF, and COX-2 through a decrease in the intracellular Ca2+ levels, and also showed a suppression of the ERK 1/2, JNK 1/2, and NF-κB activation. These results indicated that luteolin from the flowers of Lonicera japonica exerted a regulatory effect on mast cell-mediated inflammatory diseases, such as RA, allergy disease and IBD.

Methyl gallate is a major component of Galla Rhois, as carvacrol is of oregano essential oils. Both have shown good antibacterial activity against intestinal bacteria. This study investigated the antibacterial activities of nalidixic acid in combination with methyl gallate and carvacrol against nalidixic acid resistant bacteria. The combined effect of nalidixic acid with methyl gallate and carvacrol was evaluated using the checkerboard method to obtain a fractional inhibitory concentration index. The results showed that the combinations of nalidixic acid + methyl gallate/carvacrol improved nalidixic acid resistant pathogenic bacteria inhibition with synergy or partial synergy activity. Thus, a strong bactericidal effect of the drug combinations was observed. In vitro data thus suggested that nalidixic acid combined with methyl gallate and carvacrol may be microbiologically beneficial, rather than antagonists.

Punica granatum is commonly used in Korea as a traditional medicine for the treatment of pathogenic bacteria. In this study, we investigated the in vitro and in vivo antimicrobial activity of P. granatum peel EtOH extract (PGPE) against 16 strains of Salmonella. The minimal inhibitory concentrations of PGPE were in the range of 62.5–1000 x03BCg mL−1. In addition, the in vivo antibacterial activity of the PGPE extract was examined in a S. typhimurium infection mouse model. Mice were initially infected with S. typhimurium and then with PGPE. The extract was found to have significant effects on mortality and the numbers of viable S. typhimurium recovered from feces. Although clinical signs and histological damage were rarely observed in the treated mice, the untreated controls showed signs of lethargy and histological damage in the liver and spleen. Taken together, the results of this study indicate that PGPE has the potential to provide an effective treatment for salmonellosis.

Mume Fructus (Family Rosaceae) is used as a traditional drug and health food in Asian countries. However, its therapeutic mechanisms and effects on macrophage-mediated inflammation remain unknown. In this study we examined the effect of Mume Fructus water extract (MFWE) on pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The investigation focused on whether MFWE inhibited nitric oxide (NO) and prostaglandin (PG) E2 productions, as well as the expressions of inducible NO synthase (iNOS), cyclooxygenase (COX)-2, interleukin (IL)-6, nuclear factor-kappaB (NF-kappaB), and mitogen-activated protein kinases (MAPKs) in LPS-stimulated RAW 264.7 cells. We found that MFWE inhibited LPS-induced NO, PGE(2), and IL-6 productions as well as the expressions of iNOS and COX-2. Furthermore, MFWE suppressed the LPS-induced phosphorylations of p38 MAPK and extracellular signal-regulated kinase MAPK, as well as IkappaBalpha degradation and NF-kappaB activation. These results suggest that MFWE has inhibitory effects on LPS-induced PGE2, NO, and IL-6 production, as well as the expressions of iNOS and COX-2 in the murine macrophage. These inhibitory effects occur through blockades on the phosphorylation of MAPKs following IkappaBalpha degradation and NF-kappaB activation.

Sanguinarine is a benzophenanthridine alkaloid derived from the root of Sanguinaria canadensis. It is known to perform a wide spectrum of biological activities. The aim of this study is to examine the antimicrobial actions of sanguinarine against methicillin-resistant Staphylococcus aureus (MRSA). Sanguinarine antimicrobial activity was assessed by broth dilution method; its mechanism of action was investigated by bacteriolysis, detergent or ATPase inhibitors and transmission electron microscopy were used to monitor the survival characteristics and the changes in bacteria morphology. The activity of sanguinarine against MRSA strains ranged from 3.12 to 6.25 µg/ml, while the minimum inhibitory concentrations of the two reference strains are 3.12 µg/ml and 1.56 µg/ml. The treatment of the cells with sanguinarine induced the release of membrane-bound cell wall autolytic enzymes, which eventually resulted in lysis of the cell. The OD(600s) of the suspensions treated with the combination of Tris-(hydroxymethyl) aminomethane and Triton X-100 with sanguinarine were reduced to 40% and 8%, respectively. Transmission electron microsco-py of MRSA treated with sanguinarine showed alterations in septa formation. The predisposition of lysis and the altered morphology seen by transmission electron microscopy suggest that sanguinarine compromises the cytoplasmic membrane.