Propyl Gallate Research Articles

Quality-by-Design-Based Development of n-Propyl-Gallate-Loaded Hyaluronic-Acid-Coated Liposomes for Intranasal Administration

The present study aimed to develop n-propyl gallate (PG)-encapsulated liposomes through a novel direct pouring method using the quality-by-design (QbD) approach. A further aim was to coat liposomes with hyaluronic acid (HA) to improve the stability of the formulation in nasal mucosa. The QbD method was used for the determination of critical quality attributes in the formulation of PG-loaded liposomes coated with HA. The optimized formulation was determined by applying the Box–Behnken design to investigate the effect of composition and process variables on particle size, polydispersity index (PDI), and zeta potential. Physiochemical characterization, in vitro release, and permeability tests, as well as accelerated stability studies, were performed with the optimized liposomal formulation. The optimized formulation resulted in 90 ± 3.6% encapsulation efficiency, 167.9 ± 3.5 nm average hydrodynamic diameter, 0.129 ± 0.002 PDI, and −33.9 ± 4.5 zeta potential. Coated liposomes showed significantly improved properties in 24 h in an in vitro release test (>60%), in vitro permeability measurement (420 μg/cm2) within 60 min, and also in accelerated stability studies compared to uncoated liposomes. A hydrogen-peroxide-scavenging assay showed improved stability of PG-containing liposomes. It can be concluded that the optimization of PG-encapsulated liposomes coated with HA has great potential for targeting several brain diseases.

Co-encapsulation of vegetable oils with phenolic antioxidants and evaluation of their oxidative stability under long-term storage conditions

The aim of this study is to evaluate the feasibility of edible oils co-encapsulation with antioxidants in a natural protein matrix obtained using the spray-drying method, and to demonstrate the long-term stability of microparticles. Sunflower and flaxseed oils were encapsulated in pea protein isolate (PP) with a hydrophilic antioxidant, propyl gallate (PG), and a lipophilic antioxidant, α-tocopherol (α-T). Samples with encapsulated oil and the corresponding unencapsulated oil were then stored at 25 °C for up to 10 months (300 days) to monitor the long-term oxidative stability. The results demonstrated that microencapsulation, the addition of antioxidants, as well as the nature of the oil all affected the oxidative stability of oils. The addition of PG made it possible the increase in oil stability during the total storage period, whereas α-T had a pro-oxidant effect and induced the decrease in oil resistivity to oxidation. The positive effect of PG was more pronounced for short storage times (t < 100 days). Flaxseed oil, which is more sensitive to oxidation, showed slower oxidation kinetic after encapsulation compared to sunflower oil. The proposed encapsulation method may be an efficient approach for enhancing oxidative stability of edible oils for functional food powders.

Comparison of antioxidant activities of selected phenolic compounds in O/W emulsions and bulk oil

Antioxidant activities of 1-o-galloylglycerol (GG), propyl gallate, rosmarinic acid (RA), tocopherols (TOC), and 1:1 combinations of GG/RA and GG/TOC were evaluated using in vitro assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS+), and ferric reducing antioxidant power (FRAP). Soybean oil stripped of TOC was utilized as bulk oil and as the oil phase in O/W emulsions for accelerated oxidation test with the selected phenolic compounds. Efficacies of antioxidants were evaluated by monitoring total oxidation (TOTOX) values and fatty acid profiles of oil and O/W samples during the accelerated oxidation. In bulk oil, GG outperformed other singular antioxidants, preventing 39.04% of oxidation for ω-3 fatty acids with a TOTOX value of 166.68. In emulsions, TOC outperformed other singular antioxidants, preventing 38.04% of oxidation with a TOTOX value of 196.72. Considering the polarities of the antioxidants and our testing systems, these results provide supporting evidence for the polar paradox theory.

Myofibrillar Protein Cross-Linking and Gelling Behavior Modified by Structurally Relevant Phenolic Compounds.

Protein gelation is an important phenomenon in processed meats. The present study investigated the structure-activity relationship of six phenolic compounds, that is, gallic acid (GA), chlorogenic acid (CA), propyl gallate (PG), quercetin (QT), catechin (CC), and (-)-epigallocatechin-3-gallate (EGCG) in a myofibrillar protein (MP) gelling system under controlled oxidative conditions. All phenolics induced unfolding and promoted cross-linking of MP via sulfhydryl or amine groups. At an equal molar concentration, EGCG boosted the elastic MP gel network more than other phenolics except PG. However, all three monophenols (GA, CA, and PG) and the diphenol QT increased the MP gel strength more than CC (diphenol) and EGCG (triphenol). The flavanol structure appeared to interfere with the protein gel structure development. All phenolics retarded lipid oxidation in MP-emulsion composite gels during refrigerated storage with the least polar phenolic compounds, PG and QT, showing the greatest efficacy.

Govaniadine Ameliorates Oxidative Stress, Inflammation, and Kupffer Cell Activation in Carbon Tetrachloride-Induced Hepatotoxicity in Rats.

Liver diseases such as hepatic carcinoma are one of the main health problems worldwide. Herbal drugs are largely used to treat liver injury in the indigenous system of medicine and may provide lead compounds for hepatoprotective drug discovery. The present study is investigated to test the Corydalis govaniana Wall. extract, fraction, and isolate therapeutically active constituents to explore their hepatoprotective, anti-inflammatory, and antioxidant activities. For this purpose, the antioxidant activity of govaniadine, caseadine, caseamine, and protopine was performed by assessing the scavenging events of the stable 2,2-diphenyl-1-picrylhydrazyl. Hepatoprotection of govaniadine was assessed in terms of reduction in serum enzymes (alanine aminotransferase, aspartate transaminase, and alkaline phosphatase) caused by CCl4-induced liver injury in rats and by histopathological techniques. All the compounds showed significant antioxidant activity with a percentage inhibition of 92.2, 86.7, 85.3, and 79.7, respectively, compared to propyl gallate 90.3%. Treatment with govaniadine reduced the serum enzyme level down to normal levels in the CCl4-treated group while inhibiting the increase of malondialdehyde, and the induction of superoxide dismutase and the glutathione level was upregulated. Histopathology showed ∼47% damage to the liver cells in the CCl4-treated group; reduction in this damaged area was found to be better upon using govaniadine. Immunohistochemistry results showed that govaniadine as compared to silymarin has exceedingly decreased the inflammation by halting the CCl4-induced activation of hepatic macrophages. In carrageenan-induced paw edema assay, govaniadine significantly alleviated the edema after 1–5 h at a dose of 20 mg/kg (26.00 and 28.5%), 50 mg/kg (22.05 and 27.0%), and 100 mg/kg (20.02 and 25.30%), respectively. The results of our experiments suggest that govaniadine showed antioxidant and hepatoprotective activity in liver injury. The hepatoprotective function of govaniadine may be associated to the scavenging of the free radical and attenuation of oxidative stress as well as inflammatory responses in the liver. Hence, govaniadine may be a lead compound for the hepatoprotective drug discovery process and further research is needed to find out their molecular mechanism of protection.

Fine-tuning mitochondrial activity in Yarrowia lipolytica for citrate overproduction

Yarrowia lipolytica is a non-conventional yeast with promising industrial potentials for lipids and citrate production. It is also widely used for studying mitochondrial respiration due to a respiratory chain like those of mammalian cells. In this study we used a genome-scale model (GEM) of Y. lipolytica metabolism and performed a dynamic Flux Balance Analysis (dFBA) algorithm to analyze and identify metabolic levers associated with citrate optimization. Analysis of fluxes at stationary growth phase showed that carbon flux derived from glucose is rewired to citric acid production and lipid accumulation, whereas the oxidative phosphorylation (OxPhos) shifted to the alternative respiration mode through alternative oxidase (AOX) protein. Simulations of optimized citrate secretion flux resulted in a pronounced lipid oxidation along with reactive oxygen species (ROS) generation and AOX flux inhibition. Then, we experimentally challenged AOX inhibition by adding n-Propyl Gallate (nPG), a specific AOX inhibitor, on Y. lipolytica batch cultures at stationary phase. Our results showed a twofold overproduction of citrate (20.5 g/L) when nPG is added compared to 10.9 g/L under control condition (no nPG addition). These results suggest that ROS management, especially through AOX activity, has a pivotal role on citrate/lipid flux balance in Y. lipolytica. All taken together, we thus provide for the first time, a key for the understanding of a predominant metabolic mechanism favoring citrate overproduction in Y. lipolytica at the expense of lipids accumulation.

Клонирование, выделение и изучение свойств новой рекомбинантной танназы Aspergillus niger

A new recombinant Aspergillus niger tannase (tannin acyl hydrolase) produced by the Penicillium verruculosum fungus has been studied. A strain with a high level of extracellular tannase (TAN2) secretion (80% of the total extracellular protein) was obtained by cloning the tan2 gene (PDB Acc. No: MT828303) into the recipient strain. The tannase enzyme preparation degraded tannins in black tea extracts. TAN2 was isolated in homogeneous form using chromatographic methods; the enzyme had a high activity against gallotannin (53 U/mg) and less activity against propyl gallate (4.7 U/mg). Homogeneous TAN2 showed temperature and pH optima of 45 °C and 3.5, respectively. At a temperature of 50 °C, TAN2 retained above 80% activity for 3 h; at 60 °C, it retained about 75% of its activity for 90 min; at 70 °C, the enzyme was completely inactivated within 10 min. Tannase was characterized by a high tolerance to NaCl, the activity against gallotannin exceeded 50% of the initial value in solutions with a salt concentration of up to 5 M. The tannase activity was stimulated by Ca2+, Mg2+, Zn2+, Mn2+, Cu2+, Cd2+, Pb2+ by 3--64% and inhibited by 4-65% in the presence of Co2+, Fe3+ and Fe2+ ions. tannase, tannins, Aspergillus niger, Penicillium verruculosum This work was supported by the Ministry of Science and Higher Education of the Russian Federation.

Micro-mechanism study on different antioxidants protective effect of vegetable oil by ReaxFF molecular dynamics

The aging problem of vegetable oil has severely restricted the popularization and application of vegetable oil transformers. Adding antioxidants is the most recommended solution. At present, there is insufficient research on the micro-mechanism of the protective effect of antioxidants on vegetable oil. In this paper, multiple vegetable oil models with different types and concentrations of antioxidants were established. Then the molecular dynamics simulation based on ReaxFF was carried out at different temperatures and oxygen content. Results show that the protective mechanism of antioxidants is to release H and combine with free radicals generated by the decomposition of unsaturated fatty acids (UFA) in the oil. In addition, the protective effects of four antioxidants are different. The stronger ones are tert-butyl hydroquinone (TBHQ) and butylated hydroxytoluene (BHT), while the weaker ones are butylated hydroxyanisole (BHA) and propyl gallate (PG). TBHQ has a better protective effect at low concentration, but the decomposition of UFA is promoted at high concentration. When the temperature rises, the decomposition of UFA would be promoted. With the addition of oxygen, small molecular compounds are easily oxidized, and the decomposition of UFA is accelerated. The above research could reveal the microscopic mechanism of antioxidant protection on vegetable oil, providing theoretical reference for further exploration of effective vegetable oil aging protection technology.

Development of a Web-Based Toolbox to Support Quantitative In-Vitro-to-In-Vivo Extrapolations (QIVIVE) within Nonanimal Testing Strategies.

The goal of the present study was to develop an online web-based toolbox that contains generic physiologically based kinetic (PBK) models for rats and humans, including underlying calculation tools to predict plasma protein binding and tissue:plasma distribution, to be used for quantitative in-vitro-to-in-vivo extrapolations (QIVIVE). The PBK models within the toolbox allow first estimations of internal plasma and tissue concentrations of chemicals to be made, based on the logP and pKa of the chemicals and values for intestinal uptake and intrinsic hepatic clearance. As a case study, the toolbox was used to predict oral equivalent doses of in vitro ToxCast bioactivity data for the food additives methylparaben, propyl gallate, octyl gallate, and dodecyl gallate. These oral equivalent doses were subsequently compared with human exposure estimates, as a low tier assessment allowing prioritization for further assessment. The results revealed that daily intake levels of especially propyl gallate can lead to internal plasma concentrations that are close to in vitro biological effect concentrations, particularly with respect to the inhibition of human thyroid peroxidase (TPO). Estrogenic effects were not considered likely to be induced by the food additives, as daily exposure levels of the different compounds remained 2 orders of magnitude below the oral equivalent doses for in vitro estrogen receptor activation. Overall, the results of the study show how the toolbox, which is freely accessible through www.qivivetools.wur.nl, can be used to obtain initial internal dose estimates of chemicals and to prioritize chemicals for further assessment, based on the comparison of oral equivalent doses of in vitro biological activity data with human exposure levels.

Phytochemical Screening, Antimicrobial and Antioxidant Activities of Sonchus Oleraceus l (Leaves) Extracts

The objective of this study to examine phytochemical analysis of sonchus oleraceus l, (asteraceae) (moliata) extracts which were extracted by four solvents, petroleum ether, chloroform, methanol and distill water and to assess their potential antibacterial against four standard bacteria gram-positive and gramnegative (bacillus subtilis staphylococcus aureu, salmonella typhi, and pscudomona aeruginosa) and antioxidant activities. (moliata) extracts using cold maceration method to extract sonchus oleraceus l, (asteraceae) locally known as (moliata) extracts, where dpph assay and paper disc diffusion assay were employed to evaluate the antioxidant and antibacterial activities respectively. The results showed that tannins, triterpenes, a sterols, flavonoids and cardiac glycosides compounds were present in the sonchus oleraceus l, (asteraceae) lives (moliata) extracts. The methanol extract of leaves showed high antioxidant potential (77± 0.03 % ) and chloroform showed low antioxidant potential activity (4±0.09) compare with propyl gallate as standard (93± 0.010 %) against dpph. Chloroform extract was effective and give moderate zone of inhibition against staphylococcus aureus. Methanol extract was effective and showed moderate zone of inhibition against staphylococcus aureus, bacillus subtilis, salmonella typhi and pseudomonas aeruginosa.

Antioxidant effects of gallic acid alkyl esters of various chain lengths in oyster during frying process

SummaryThe antioxidant effects of gallic acid (GA) and its alkyl esters including methyl gallate, ethyl gallate, propyl gallate, butyl gallate (GA‐C4), octyl gallate, lauryl gallate, hexadecyl gallate and octadecyl gallate in frying oil (soybean oil) and oyster during frying were investigated. Rancimat induction period (RIP) assay indicated GA and its alkyl esters effectively improved the oxidative stability of soybean oil according to the ‘polar paradox’; that is, the antioxidant effects of the polyphenols decreased in lipid system with the increasing of hydrophobicity. Results also indicated that GA and its alkyl esters all effectively retarded lipid oxidation in oyster tissue according to parameters including RIP, peroxide value and electron spin resonance assays. Moreover, the antioxidant efficiency in oyster increased with the alkyl chain length until GA‐C4, and thereafter, the antioxidant effects decreased, similar to the ‘cut‐off effect’. This study provides basic data for improving the oxidative stability of seafood during frying.

Phytochemical Screening of Leaves from Mangifera indica and Morus alba for Bioactive Compounds

The aqueous, methanol and DMSO extracts from leaves of Mangifera indica and Morus alba were screened for bioactive compounds. Antimicrobial activity and MIC (mg/ml) were determined using agar-well diffusion and serial dilution methods respectively against human pathogenic bacteria and fungi. Antioxidant activities (%) were determined against DPPH free radicals, superoxide anion and Fe+2 whereas antiurease activity (%) was by indophenol method. The time taken to set paralysis and death of Pheritima posthuma was observed after released into extract. Phytochemical analysis detected carbohydrates, alkaloids, phenols, flavonoids, terpenoids, saponins, tannins, steroids, resins, anthraquinones, cardiac glycosides and phlobatannins. All extracts more or less showed the activity against Gram-positive and -negative bacteria producing zone of inhibition 15±0.57 to 43.66±0.66 mm and MIC values 13±1.64 to 100±0.35 mg/ml. Similarly, for fungi, zone of inhibition and MIC values were 9±0.57 to 34±0.57 mm and 23±1.25 115±0.55 g/ml respectively. Activities against DPPH, superoxide anion and Fe+2 free radicals were found 13.68±0.74 to 93.70±0.76 %, 50.23±0.43 to 95.7±0.21 % and 52.76±0.23 to 98.82±0.42% respectively, of these, the maximum activities surpassed the n-propyl gallate (91.31 %) and EDTA (98.05 %). Similarly, urease was also inhibited (33 to 95.23%) by all extracts. All extracts were also caused paralysis followed by subsequent death (13.5/26.87 to 39/60.06 min) of P. posthuma, of these methanolic extract from M. indica was least than that by albendazole (30.45/52 min) and piperazine citrate (14.35/36 min). The results provide scientific basis for traditional use of these extracts as affordable strategies for treatments of infectious, inflammatory and degenerative diseases, caused by bacteria, fungi, free radicals, urease and helminths.

Agaricus bisporus Crude Extract: Characterization and Analytical Application.

In the present work crude Agaricus bisporus extract (ABE) has been prepared and characterized by its tyrosinase activity, protein composition and substrate specificity. The presence of mushroom tyrosinase (PPO3) in ABE has been confirmed using two-dimensional electrophoresis, followed by MALDI TOF/TOF MS-based analysis. GH27 alpha-glucosidases, GH47 alpha-mannosidases, GH20 hexosaminidases, and alkaline phosphatases have been also detected in ABE. ABE substrate specificity has been studied using 19 phenolic compounds: polyphenols (catechol, gallic, caffeic, chlorogenic, and ferulic acids, quercetin, rutin, dihydroquercetin, l-dihydroxyphenylalanine, resorcinol, propyl gallate) and monophenols (l-tyrosine, phenol, p-nitrophenol, o-nitrophenol, guaiacol, o-cresol, m-cresol, p-cresol). The comparison of ABE substrate specificity and affinity to the corresponding parameters of purified A. bisporus tyrosinase has revealed no major differences. The conditions for spectrophotometric determination have been chosen and the analytical procedures for determination of 1.4 × 10−4–1.0 × 10−3 M l-tyrosine, 3.1 × 10−6–1.0 × 10−4 M phenol, 5.4 × 10−5–1.0 × 10−3 M catechol, 8.5 × 10−5–1.0 × 10−3 M caffeic acid, 1.5 × 10−4–7.5 × 10−4 M chlorogenic acid, 6.8 × 10−5–1.0 × 10−3 M l-DOPA have been proposed. The procedures have been applied for the determination of l-tyrosine in food supplements, l-DOPA in synthetic serum, and phenol in waste water from the food manufacturing plant. Thus, we have demonstrated the possibility of using ABE as a substitute for tyrosinase in such analytical applications, as food supplements, medical and environmental analysis.

Chemical and Biological Activities of Deverra triradiata Hochst. ex. Boiss. Aerial parts from St.Catherine, Southern Sinai, Egypt.

The present study describe the phenolic and flavonoid profiles of the ethyl acetate extract of D. triradiata which have been demonstrated by high-performance liquid chromatography (HPLC) to prove the presence of 15 compounds, nine major compounds namely, querectin (46.37 mg/g), vanillin (11.94),daidzein (10.02),ellagic acid (4.76), propyl gallate (3.89), naringenin (3.27), gallic Acid (3.18 mg/g), rutin (2.7) and chlorogenic Acid (2.58). The chemical constituents of unsaponifiable portion of petroleum ether 60-80o extract which analyzed by gas-liquid chromatography (GLC) proved the presence of 14 hydrocarbons and three sterol; n-eicosane (16.94%), n-docosane (8.22 %), n-heptadecane (7.13 %),squalene (6.89%), n-tricosane (1.63 %), n-hendecane (1.63 %), cholesterol (1.12 %), campesterol (3.81 %) and stigmasterol (5.27 %).The saponifiable portion five unsaturated fatty acids were indicated as,α-Linolenic acid (17.95 %), arachidonic acid (11.37), linolenic acid (6.12),oleic acid (3.36) and palmitoleic acid (3.01) and also four saturated fatty acid named by, palmitic acid (31.61), myristic acid (7.17), Lauric acid (1.67) and stearic acid (1.47).Total phenolic (tannic acid equivalent), total tannins (tannic acid equivalent) and total flavonoids (quercetin equivalent) were (67.8±0.39, 31.4 ± 0.63 and 4.7 ± 0.077 mg/g d.w.), respectively. The in vitro antioxidant activity using the stable free radical DPPH (2,2-diphenyl-1-pycrylhydrazyl) method of the petroleum ether and ethyl acetate extracts . The percentage of maximal inhibition for extracts in DPPH are 18.42 ± 0.39 and 43.58±0.52 %, respectively compared with percentage of gallic acid 91.29 ±0.72μg/ml, which proved that ethyl acetate extract possesses a distinct radical scavenging effect, which may be attributed to its high polyphenolic content.The in vitro cytotoxic activity by using SRB assay, of petroleum ether showed promising activity against (MCF7), (PC3) and (HCT 116) with IC50 18.8, 9.3 and 9.5 ug/ml, respectively, compared with normal cell. Baby Hamster kidney (BHK) with IC50 37, while, the ethyl acetate extract showed weak activity against (MCF7), (PC3) and (HCT) with IC50 42, 42 and 37 ug/ml, comparable to (BHK) normal cell with IC50 59 μg/ml. All identified phenolic compounds are therapeutically active compounds with anticancer potency and antioxidant capacities which were reported for the first time.

Molecular Identification, Antioxidant Efficacy of Phenolic Compounds, and Antimicrobial Activity of Beta-Carotene Isolated from Fruiting Bodies of Suillus sp

Suillus species, in general, are edible mushrooms, and environmentally important that are associated mostly with pine trees in the tropics regions. These fungi considered a remarkable source of phenolic compounds that play a crucial role as antioxidants which may reduce the risk of most human chronic diseases such as cancer, diabetes, asthma, atherosclerosis, Alzheimer, and others. On the other hand, carotenoids (\b{eta} carotene) are the most popular natural pigments which play an important role to protect the plants from photo-oxidative reactions. In human, these compounds prevent oxidative stress and expects to have antimicrobial activity. Here, the phenolic compounds were extracted with Ethyl acetate from fruiting bodies of Suillus sp and analyzed by HPLC, the antioxidant activity (reducing power%) of phenolic compounds was determined at the concentrations of 1, 2.5, and 5 mg/mL. Antimicrobial activity of \b{eta} carotene pigment was measured at a concentration of 100 mg/mL against some human pathogenic bacteria such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, and Staphylococcus aureus. The specific DNA region ITS was amplified and sequenced using ITS1 and ITS4 primers with some bioinformatics analyses. The phenolic extract isolated from fruiting bodies of Suillus sp showed a remarkable antioxidant activity by increasing the reducing power percent (from F+3 ions to F+2 ions) comparing with the industrial antioxidant (Propyl gallate) at all used concentrations. Percent of reducing power of phenolic compounds were 75.5, 84.9 and 95.7% at concentrations of 1, 2.5, and 5 mg/mL respectively; comparing with PG were 65.9, 81.3, and 93.3 at 1, 2.5, and 5 mg/mL respectively. The \b{eta} carotene pigment revealed a significant antimicrobial activity at a concentration of 100 mg/mL against K. pneumonia, E. coli, and S. aureus.

Solvent-free enzymatic synthesis of 1,2-dipalmitoylgalloylglycerol: Characterization and optimization of reaction condition

A novel diacylglycerol-based galloyl structured lipid, 1,2-dipalmitoylgalloylglycerol (DPGG), was synthesized using the enzymatic transesterification of propyl gallate (PG) and tripalmitin under solvent-free condition. An immobilized and commercially available food-grade Candida antarctica lipase B, Lipozyme® 435, was used as the biocatalyst. The reaction variables that affect the yield of DPGG were optimized using a 33 full factorial design. At 70 °C, DPGG was obtained at a yield of 33.0 ± 2.0% with PG conversion at 44.8 ± 1.8% when the following condition was used: 25 substrate molar ratio of tripalmitin to PG, 120 h reaction time, and 25% enzyme load relative to the total substrate weight. The structure of reaction product was elucidated using Fourier-transform infrared spectroscopy (FT-IR), electrospray ionization high-resolution accurate-mass tandem mass spectrometry (ESI-HRAM-MS/MS), and 1D and 2D nuclear magnetic resonance spectroscopy (NMR). The effects of different lipases and galloyl donors/acceptors on the transesterification were also investigated.

Gallic acid and its alkyl esters emerge as effective antioxidants against lipid oxidation during hot air drying process of Ostrea talienwhanensis

The antioxidant efficiency of gallic acid (GA) and its alkyl esters including methyl gallate (MG), ethyl gallate (EG), propyl gallate (PG), butyl gallate (BG), octyl gallate (OG), lauryl gallate (LG), hexadecyl gallate (HG), and octadecyl gallate (SG) in oyster tissue during hot-air drying process was investigated. Results indicated that GA and its alkyl esters all could effectively retard lipid oxidation in oyster tissue according to peroxide value (POV), thiobarbituric acid reactive substances (TBARS) and free radical intensity. The antioxidant effects increased with the alkyl chain length until OG, thereafter, it gradually decreased. The POV of the OG treated oysters post 10 h of drying was 66.26, 68.90, 77.86, 92.61, 89.45, 70.79, 68.96 and 62.70%, respectively, of those treated by GA, MG, EG, PG, BG, LG, HG and SG. The corresponding values for TBARS were 68.72, 76.59, 77.88, 84.32, 86.23, 68.31, 81.24, 77.36%, while 41.19, 58.62, 62.83, 64.49, 69.60, 61.44, 60.05 and 72.61% for free radical intensity. Pearson correlation analysis showed a positive correlation between the antioxidant effects and the concentrations of the polyphenol compounds in oyster tissue. This report will provide the basic data for selection of suitable antioxidants to improve the oxidation stability of seafood during thermal processing.

Screening of antimicrobial synergism between phenolic acids derivatives and UV-A light radiation

The objective of this study was to investigate synergistic antibacterial activity based on a combination of UV-A light and three classes of food grade compounds: benzoic acid derivatives, cinnamic acid derivatives, and gallates. By using Escherichia coli O157:H7 as the model strain, it was observed that three cinnamic acid derivatives (ferulic acid, coumaric acid, and caffeic acid) and one benzoic acid derivative (2,5-dihydroxybenzoic acid) presented strong synergistic antibacterial activity with UV-A light radiation, where 1 mM levels of these compounds plus with 15 min of UV-A light (total light dose of 6.1 cm−2) led to more than 7-log CFU mL−1 of bacterial inactivation. In contrast, synergistic antibacterial activity between UV-A light and most benzoic acid derivatives (benzoic acid, gallic acid, vanillic acid, and 2,5-dimethoxybenzoic acid) were only observed after higher concentrations of these compounds were applied (10 mM). Lastly, from the three gallates tested (methyl gallate, ethyl gallate, and propyl gallate), only propyl gallate showed strong antibacterial synergism with UV-A light, where 10 mM of propyl gallate plus 15 min of UV-A light led to approximately 6.5-log of bacterial reduction. Presence of antioxidant compounds mitigated the light-mediated antibacterial activity of gallic acid, 2,5-dihydroxybenzoic acid, and propyl gallate. Similarly, the light-mediated antibacterial activity of these compounds was significantly (P < 0.05) reduced against metabolic-inhibited bacterial cells (sodium azide pretreatment). On the other hand, the antibacterial synergism between ferulic acid and UV-A light was not affected by the presence of antioxidants or the metabolic state of the bacterial cells. Due to the increasing concerns of antimicrobial resistant (AMR) pathogens, the study also investigated the proposed synergistic treatment on AMR Salmonella. Combinations of 1 mM of ferulic acid or 1 mM of 2,5-dihydroxybenzoic acid with UV-A light radiation was able to inactivate more than 6-log of a multi-drug resistant Salmonella Typhimurium strain.

Dual-ratiometric electrochemical sensor for propyl gallate detection

A dual-ratiometric electrochemical sensor was constructed for propyl gallate (PG) detection based on anthraquinone/multi-walled carbon nanotube/chitosan modified glassy carbon electrode (AQ/MWCNT/CS/GCE). In the presence of the analyte PG, the AQ/MWCNT/CS/GCE displays three current peaks at different potentials, which are respectively related to the electro-oxidation of PG, AQ, and MWCNT. Anthraquinone and multi-walled carbon nanotube can be then used as inner reference electroactive probes. It was demonstrated that the modification of the GCE with AQ, MWCNT and chitosan can enhance the electrochemical signal of PG, leading to the improvement in the sensitivity of PG detection. Two ratiometric signals, namely, IPG/IAQ and IPG/IMWCNT, linearly increase with the increasing concentration of PG over the range of 1.0 to 30.0 μM, and the detection limit for PG detection are respectively estimated to be 0.67 μM and 0.76 μM. The electrochemical sensor can be applied for PG detection in edible oil samples with satisfactory results.

Reversal of Tetracycline Resistance by Cepharanthine, Cinchonidine, Ellagic Acid and Propyl Gallate in a Multi-drug Resistant Escherichia coli

Bacterial resistance to antibiotics is an increasing threat to global healthcare systems. We therefore sought compounds with potential to reverse antibiotic resistance in a clinically relevant multi-drug resistant isolate of Escherichia coli (NCTC 13400). 200 natural compounds with a history of either safe oral use in man, or as a component of a traditional herb or medicine, were screened. Four compounds; ellagic acid, propyl gallate, cinchonidine and cepharanthine, lowered the minimum inhibitory concentrations (MICs) of tetracycline, chloramphenicol and tobramycin by up to fourfold, and when combined up to eightfold. These compounds had no impact on the MICs of ampicillin, erythromycin or trimethoprim. Mechanistic studies revealed that while cepharanthine potently suppressed efflux of the marker Nile red from bacterial cells, the other hit compounds slowed cellular accumulation of this marker, and/or slowed bacterial growth in the absence of antibiotic. Although cepharanthine showed some toxicity in a cultured HEK-293 mammalian cell-line model, the other hit compounds exhibited no toxicity at concentrations where they are active against E. coli NCTC 13400. The results suggest that phytochemicals with capacity to reverse antibiotic resistance may be more common in traditional medicines than previously appreciated, and may offer useful scaffolds for the development of antibiotic-sensitising drugs.Graphic