Baoping Ji

The antibacterial mechanism of carvacrol and thymol against Escherichia coli

Aims:  To investigate the antibacterial mechanism of carvacrol and thymol against Escherichia coli.

Evaluation of Combined Antibacterial Effects of Eugenol, Cinnamaldehyde, Thymol, and Carvacrol against E. coli with an Improved Method

In this study, the antibacterial activities of eugenol, cinnamaldehyde, thymol, carvacrol, and their combinations against E. coli were investigated separately. First, broth macro-dilution assay was adopted to determine the minimal inhibitory concentration (MIC) of the 4 components. Second, the combination testing was performed using chequerboard method. Finally, the combined effects were evaluated with an improved method, which was based on the indices of fractional inhibitory concentration (FIC) and Effect of the Combination (EC) jointly. The results indicated that MICs of the 4 components were 1600, 400, 400, and 400 mg/L, respectively; treatments with cinnamaldehyde/eugenol, thymol/eugenol, carvacrol/eugenol, and thymol/carvacrol revealed synergistic effects according to the 2 indices. By means of combination, MICs of eugenol, cinnamaldehyde, thymol, and carvacrol decreased to 400, 100, 100, and 100 mg/L, respectively. Consequently, the negative impacts of unpleasant smell of these 4 components could be minimized, making it possible to add them to foods as preservatives. In addition, this improved evaluation method provided a more accurate and comprehensive way to evaluate combined effects.

Synergistic effect of thymol and carvacrol combined with chelators and organic acids against Salmonella Typhimurium.

To identify synergistic combinations of different food additives, the antimicrobial effects of thymol and carvacrol against Salmonella Typhimurium were assessed alone and in combination with various other preservatives including EDTA, acetic acid, lactic acid, and citric acid. Overall, growth of Salmonella Typhimurium was significantly inhibited in Mueller-Hinton broth containing thymol, carvacrol, EDTA, acetic acid, lactic acid, or citric acid at concentrations of 400 mg/liter, 400 microl/liter, 300 mg/liter, 0.2% (vol/vol), 0.2% (vol/vol), and 0.2% (wt/vol), respectively. The combination of different antimicrobials such as thymol or carvacrol with EDTA, thymol or carvacrol with acetic acid, and thymol or carvacrol with citric acid all resulted in significantly reduced populations of Salmonella Typhimurium. In samples treated with combinations, these antimicrobials had synergistic effects compared with samples treated with thymol, carvacrol, EDTA, acetic acid, or citric acid alone. However, the combined use of lactic acid with thymol or carvacrol did not produce a synergistic effect against Salmonella Typhimurium. Thus, some chelators or organic acids can be used as food preservatives in combination with thymol and carvacrol to reduce the concentrations needed to produce an adequate antimicrobial effect.

Comparative study of the effects of solid-state fermentation with three filamentous fungi on the total phenolics content (TPC), flavonoids, and antioxidant activities of subfractions from oats (Avena sativa L.).

The aim of present work was to investigate the effect of solid-state fermentation with filamentous fungi (Aspergillus oryzae var. effuses, Aspergillus oryzae, and Aspergillus niger) on total phenolics content (TPC), flavonoids, and antioxidant activities of four subfractions of oat, namely, n-hexane, ethyl acetate (EA), n-butanol, and water, and compare them to their corresponding subfractions of unfermented oat. The TPC and total flavonoids increased dramatically, especially in EA subfractions (p < 0.05). The levels of antioxidant activity of subfractions were also significantly enhanced (p < 0.05). The highest antioxidant activities were also found in the EA subfractions. The polyphenols in EA were analyzed by high-performance liquid chromatography at 280 nm. Most polyphenols were increased remarkably, especially ferulic and caffeic acids. There was a clear correlation between the TPC and antioxidant activity. In conclusion, fungi fermentation is a potential bioprocess for increasing the TPC, flavonoids, and antioxidant activities of oat-based food.

In Vitro Inhibitory Effect on Pancreatic Lipase Activity of Subfractions from Ethanol Extracts of Fermented Oats (Avena sativa L.) and Synergistic Effect of Three Phenolic Acids

The purpose of the present work is to study the pancreatic lipase inhibitory effects of different subfractions (n-hexane, ethyl acetate (EA), n-butanol, and water) from ethanol extracts of nonfermented and fungi-fermented oats and to delineate the interactions of three primary phenolic acids in the EA subfractions. The EA subfraction showed the highest inhibitory effect on pancreatic lipase activity at 1.5 mg/mL compared to the other subfractions, regardless of whether the oats were fermented. Meanwhile, both of the EA subfractions of two fungi-fermented oats demonstrated more effective inhibitory activity than that of nonfermented oats. A positive correlation between the total phenolics content and inhibitory activity was found. The inhibitory ability of the EA subfraction from nonfermented or fermented oats also displayed a dose-dependent effect. The standards of caffeic, ferulic, and p-coumaric acids, mainly included in EA subfractions of fermented oats, also displayed a dose-dependent inhibitory effect. A synergistic effect of each binary combination of p-coumaric, ferulic, and caffeic acids was observed, especially at 150.0 μg/mL. Those results indicate that fungi-fermented oats have a more effective inhibitory ability on pancreatic lipase and polyphenols may be the most effective component and could be potentially used for dietary therapy of obesity.

Inhibitory Effect of Blueberry Polyphenolic Compounds on Oleic Acid-Induced Hepatic Steatosis in Vitro

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide and is closely associated with metabolic syndromes, such as obesity, diabetes, and insulin resistance. Nonalcoholic fatty liver (NAFL), also called simple steatosis, is the initial phase of NAFLD, which is accompanied the characteristic pathological overaccumulation of lipids without inflammation. To prevent NAFLD from reaching the NAFL stage through dietary therapy, in the present work, wild Chinese blueberries (Vacciniun spp.) were selected for their well-known benefits in inhibiting metabolic syndrome. After being purified from wild Chinese blueberries, polyphenol-rich extracts were subsequently separated into three fractions, namely, anthocyanin-rich fraction, phenolic acid-rich fraction, and ethyl acetate extract. The inhibition of oleic acid (OA)-induced triglyceride (TG) deposition in HepG 2 cells was referred to as the potential activity of preventing NAFL. Biochemical indicators, such as cytotoxicity, TG level, levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and intracellular reactive oxygen species, were used to evaluate the analogous pathological stage of NAFLD. The results show that OA ≤ 1.0 mM exhibits a dose-dependent induction of TG accumulation, and no inflammation was observed based on the changes in ALT and AST levels. Therefore, 1.0 mM OA was used to simulate an in vitro fatty liver. Blueberry polyphenol-rich extract efficiently inhibited OA-induced TG accumulation in HepG2 cells, and the phenolic acid-rich fraction performed efficiently. Seven phenolic acids were subsequently identified using a high-performance liquid chromatography assay, and the main types were caffeic, chlorogenic, ferulic, p-coumaric, and cinnamic acids. These phenolic acid standards also displayed good efficiency in inhibiting TG accumulation in HepG2 cells. These results imply that wild Chinese blueberries have a potential preventive effect on NAFLD in its early stage, and phenolic acids are the most efficient component.

Analysis of the antioxidant capacities of flavonoids under different spectrophotometric assays using cyclic voltammetry and density functional theory.

Flavonoids often show inconsistent antioxidant activities (AAs) depending on the assay used. The electrochemical properties of 14 flavonoid standards in cyclic voltammetry [area under anodic wave (Q) and oxidant peak potentials (Epa)] and the structural parameters [bond dissociation enthalpy (BDE) and ionization potential (IP)] were investigated. They were compared with the results of four spectrophotometric assays, namely, diphenyl-1-picrylhydrazyl (DPPH), Folin-Ciocalteu reagent (FCR), ferric reducing ability of plasma (FRAP), Trolox equivalent antioxidant capacity (TEAC), to analyze the chemical reasons for the varying AAs of flavonoids under different assays. Using the cyclic voltammetry method, the AAs of the flavonoids in the DPPH, FCR, and FRAP assays were mainly determined by the ease of charge transferring in the first oxidation step. Meanwhile, the results of TEAC assays were primarily influenced by the amount of charge transfer in the multiple oxidation steps (MOS) of flavonoids. In the theoretical calculation, the BDE values of the selected flavonoids had considerably higher correlations with the results of the DPPH assay (r2=0.89) compared with the other three assays, which indicates that the oxidant-scavenging reaction of the tested flavonoids in the DPPH assay is closer to a hydrogen atom transfer mechanism. Neither the IP values nor BDE values had satisfactory correlation with the AAs of the flavonoids in the TEAC assay (r2=0.57, r2=0.54, respectively), Therefore, complex reaction mechanisms underlie this method and appropriate structural descriptors for reflecting the AAs of flavonoids based on MOS (e.g., TEAC values) need further investigation.

Blueberry anthocyanins: protection against ageing and light-induced damage in retinal pigment epithelial cells.

Retinal pigment epithelium (RPE) cells are vital for retinal health. However, they are susceptible to injury with ageing and exposure to excessive light, including UV (100-380 nm) and visible (380-760 nm) radiation. To evaluate the protective effect of blueberry anthocyanins on RPE cells, in vitro cell models of replicative senescent and light-induced damage were established in the present study. After purification and fractionation, blueberry anthocyanin extracts (BAE) were yielded with total anthocyanin contents of 31·0 (SD 0·5) % and were used in this study. Replicative senescence of RPE cells was induced by repeatedly passaging cells from the fourth passage to the tenth. From the fifth passage, cultured RPE cells began to enter a replicative senescence, exhibiting reduced cell proliferation along with an increase in the number of β-galactosidase-positive cells. RPE cells maintained high cell viability (P < 0·01) and a low (P < 0·01) percentage of β-galactosidase-positive cells when treated with 0·1 μg/ml BAE. In contrast, after exposure to 2500 (SD 500) lx light (420-800 nm) for 12 h, RPE cells in the positive control (light exposure, no BAE treatment) exhibited premature senescence, low (P < 0·01) cell viability and increased (P < 0·01) vascular endothelial growth factor (VEGF) release compared with negative control cells, which were not subjected to light irradiation and BAE exposure. Correspondingly, BAE is beneficial to RPE cells by protecting these cells against light-induced damage through the suppression of ageing and apoptosis as well as the down-regulation of the over-expressed VEGF to normal level. These results demonstrate that BAE is efficacious against senescence and light-induced damage of RPE cells.

Effects of Ferulic Acid and γ-Oryzanol on High-Fat and High-Fructose Diet-Induced Metabolic Syndrome in Rats

Background The high morbidity of metabolic dysfunction diseases has heightened interest in seeking natural and safe compounds to maintain optimal health. γ-Oryzanol (OZ), the ferulic acid (FA) ester with phytosterols, mainly present in rice bran has been shown to improve markers of metabolic syndrome. This study investigates the effects of FA and OZ on alleviating high-fat and high-fructose diet (HFFD)-induced metabolic syndrome parameters. Methods Male SD rats were fed with a regular rodent diet, HFFD, or HFFD supplemented with 0.05% FA or 0.16% OZ (equimolar concentrations) for 13 weeks. Food intake, organ indices, serum lipid profiles, glucose metabolism, insulin resistance (IR) index and cytokine levels were analyzed. The mechanisms were further investigated in oleic acid-stimulated HepG2 cells by analyzing triglyceride (TG) content and lipogenesis-related gene expressions. Results In the in vivo study, FA and OZ exhibited similar effects in alleviating HFFD-induced obesity, hyperlipidemia, hyperglycemia, and IR. However, only OZ treatment significantly decreased liver index and hepatic TG content, lowered serum levels of C-reactive protein and IL-6, and increased serum concentration of adiponectin. In the in vitro assay, only OZ administration significantly inhibited intracellular TG accumulation and down-regulated expression of stearoyl coenzyme-A desaturase-1, which might facilitate OZ to enhance its hepatoprotective effect. Conclusion OZ is more effective than FA in inhibiting hepatic fat accumulation and inflammation. Thus, FA and OZ could be used as dietary supplements to alleviate the deleterious effects of HFFD.

Identification of anthocyanin components of wild Chinese blueberries and amelioration of light-induced retinal damage in pigmented rabbit using whole berries.

Studies suggest that the consumption of berry fruits rich in anthocyanins may have beneficial effects on improving visual function. This study determined the total polyphenol and total anthocyanin contents in wild Chinese blueberries using the Folin-Ciocalteu reagent method and a pH differential method. Anthocyanin composition and quantity were characterized by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry coupled with mass selective detection. Total polyphenol and anthocyanin contents were 602.9 ± 9.2 and 177.8 ± 8.3 mg/100 g, respectively. Seventeen anthocyanins were discovered, and only 13 were tentatively identified in the wild blueberries. Anthocyanins of malvidin glycosylated with hexose or pentose accounted for >46% of total anthocyanin content. Furthermore, the effect of whole blueberries on retinal damage in pigmented rabbits upon light exposure was investigated, and the retinal functions were evaluated by electroretinogram (ERG). Pigmented rabbits were chosen for this experiment because of their large eyes, which facilitated the operative procedure and observation, and the similarity of their eyes to the human eye structure. Light-induced retinal damage was induced by exposure to white light at 15000 ± 1000 lx for 2 h. Feeding the rabbits with blueberries at a dosage of 1.2 or 4.9 g/kg/day for 4 weeks prior to light exposure effectively reduced photodamage to the retinas. This study adds to the growing body of data supporting the bioactivity of blueberries in improving mammal vision.