Dodecyl Gallate Research Articles

Non-antibiotic antibacterial activity of dodecyl gallate

Dodecyl (C 12) gallate (3,4,5-trihydroxybenzoate) ( 1) was found to possess antibacterial activity specifically against Gram-positive bacteria, in addition to its potent antioxidant activity. The time–kill curve study indicates that this amphipathic gallate exhibits bactericidal activity against methicillin resistant Staphylococcus aureus (MRSA) strains. Dodecyl (lauryl) gallate inhibited oxygen consumption in whole cells and oxidation of NADH in membrane preparation. The antibacterial activity of this gallate comes in part from its ability to inhibit the membrane respiratory chain. As far as alkyl gallates are concerned, their antimicrobial spectra and potency depend in part on the hydrophobic portion of the molecule.

Plasma membrane injury induced by nonyl gallate in Saccharomyces cerevisiae.

The aim was to investigate the antifungal actions of nonyl gallate against Saccharomyces cerevisiae ATCC 7754. The maximum potency of both the growth inhibitory and the fungicidal effect against the yeast strain was found in nonyl gallate among n-alkyl gallates tested. Nonyl gallate induced ROS generation dose-dependently in growing cells. This ester rapidly killed yeast cells even when cell division was restricted by cycloheximide. This ester inhibited glucose-induced medium acidification and promoted the efflux of intracellular potassium ions in a nongrowing condition. Moreover, nonyl gallate induced a leakage of calcein from artificially prepared liposomes to a greater extent than dodecyl gallate did. These results suggested nonyl gallate injured plasma membrane of S. cerevisiae, resulting in its exhibition of fungicidal effect accompanying with a leakage of intracellular materials from the cells. Our study reveals new knowledge on the antifungal actions of nonyl gallate against S. cerevisiae. When nonyl gallate is applied as a food preservative, the level of its addition to foods may be reduced because of its potent antifungal activity compared with weak acids including sorbic acid and benzoic acid.

Antioxidant activity of dodecyl gallate.

Dodecyl (C12) gallate exhibits both potent chain-breaking and preventive antioxidant activity. The pyrogallol moiety is responsible for both activities. Dodecyl (lauryl) gallate prevents generation of superoxide radicals by xanthine oxidase, and this activity comes from its ability to inhibit the enzyme. The inhibition kinetics analyzed by Lineweaver-Burk plots found that dodecylgallate is a noncompetitive inhibitor for the generation of superoxide anion. Dodecyl gallate also inhibits formation of uric acid. The inhibition kinetics analyzed by Lineweaver-Burk plots found that dodecyl gallate is a competitive inhibitor for this oxidation. Mitochondrial lipid peroxidation induced by Fe(III)-adenosine 5'-diphosphate/reduced nicotinamide adenine dinucleotide was inhibited by dodecyl gallate while its parent compound, gallic acid, did not show this inhibitory activity. Dodecyl gallate protected mitochondrial functions and human red blood cells against oxidative stresses, but gallic acid showed little effect. The hydrophobic dodecyl group is largely associated with the preventive antioxidative activity.

Antifungal activity of octyl gallate

Antifungal activities of propyl (C 3), octyl (C 8) and dodecyl (C 12) gallates (3,4,5-trihydroxybenzoate) were tested against Saccharomyces cerevisiae ATCC7754 and Zygosaccharomyces bailii ATCC 60483. Octyl gallate was found to be the only active compound with the minimum fungicidal concentration of 25 μg/ml (89 μM) against S. cerevisiae and of 50 μg/ml (177 μM) against Z. bailii, respectively. The inactivation study showed that octyl gallate was fungicidal against both S. cerevisiae and Z. bailii at any stage of growth. These fungicidal activities were not influenced by pH values. Octyl gallate at 100 μg /ml reduced plasma membrane fluidity to 48% of control. On the other hand, dodecyl gallate at the same concentration reduced it to 76% of control. Only octyl gallate inhibited glucose-induced medium acidification, indicating direct or indirect inhibition of plasma membrane H +-ATPase. The primary fungicidal activity of octyl gallate comes from its ability to act as a nonionic surface-active agent (surfactant), though it can not be inferred that membrane damage, such as a decrease in the membrane fluidity, is the only cause of the lethal effect.

Antioxidant properties of ferulic acid and its related compounds.

Antioxidant activity of 24 ferulic acid related compounds together with 6 gallic acid related compounds was evaluated using several different physical systems as well as their radical scavenging activity. The radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) decreased in the order caffeic acid > sinapic acid > ferulic acid > ferulic acid esters > p-coumaric acid. In bulk methyl linoleate, test hydroxycinnamic acids and ferulic acid esters showed antioxidant activity in parallel with their radical scavenging activity. In an ethanol-buffer solution of linoleic acid, the activity of test compounds was not always associated with their radical scavenging activity. Ferulic acid was most effective among the tested phenolic acids. Esterification of ferulic acid resulted in increasing activity. The activity of alkyl ferulates was somewhat influenced by the chain length of alcohol moiety. When the inhibitory effects of alkyl ferulates against oxidation of liposome induced by AAPH were tested, hexyl, octyl, and 2-ethyl-1-hexyl ferulates were more active than the other alkyl ferulates. Furthermore, lauryl gallate is most effective among the tested alkyl gallates. These results indicated that not only the radical scavenging activity of antioxidants, but also their affinity with lipid substrates, might be important factors in their activity.

Structure–activity relationships for inhibition of human 5α-reductases by polyphenols

The enzyme steroid 5α-reductase (EC 1.3.99.5) catalyzes the NADPH-dependent reduction of the double bond of a variety of 3-oxo-Δ 4 steroids including the conversion of testosterone to 5α-dihydrotestosterone. In humans, 5α-reductase activity is critical for certain aspects of male sexual differentiation, and may be involved in the development of benign prostatic hyperplasia, alopecia, hirsutism, and prostate cancer. Certain natural products contain components that are inhibitors of 5α-reductase, such as the green tea catechin (−)-epigallocatechin gallate (EGCG). EGCG shows potent inhibition in cell-free but not in whole-cell assays of 5α-reductase. Replacement of the gallate ester in EGCG with long-chain fatty acids produced potent 5α-reductase inhibitors that were active in both cell-free and whole-cell assay systems. Other flavonoids that were potent inhibitors of the type 1 5α-reductase include myricetin, quercitin, baicalein, and fisetin. Biochanin A, daidzein, genistein, and kaempferol were much better inhibitors of the type 2 than the type 1 isozyme. Several other natural and synthetic polyphenolic compounds were more effective inhibitors of the type 1 than the type 2 isozyme, including alizarin, anthrarobin, gossypol, nordihydroguaiaretic acid, caffeic acid phenethyl ester, and octyl and dodecyl gallates. The presence of a catechol group was characteristic of almost all inhibitors that showed selectivity for the type 1 isozyme of 5α-reductase. Since some of these compounds are consumed as part of the normal diet or in supplements, they have the potential to inhibit 5α-reductase activity, which may be useful for the prevention or treatment of androgen-dependent disorders. However, these compounds also may adversely affect male sexual differentiation.

Anti-MRSA activity of alkyl gallates

A series of alkyl gallates (3,4,5-trihydroxybenzoates) was found to show antibacterial activity against Gram-positive bacteria including methicillin resistant Staphylococcus aureus (MRSA) strains. For example, dodecyl (C 12) gallate ( 1) exhibited bactericidal activity against MRSA ATCC 33591 strain with the minimum bactericidal concentration (MBC) of 25 μg/mL (74 μM). The time–kill curve study showed that dodecyl gallate is bactericidal against this MRSA strain. This bactericidal activity comes in part from its ability to inhibit respiratory electron transport systems. The length of the alkyl chain is not a major contributor but plays an important role in eliciting the activity.

Peroxidase catalyzed grafting of gallate esters onto the polysaccharide chitosan

Peroxidases are believed to play a role in various natural polymerization processes and it may be possible to exploit peroxidases for environmentally-friendly industrial polymer processing. We examined the potential for using horseradish peroxidase to graft the phenolic substrate dodecyl gallate (DDG) onto the polysaccharide chitosan. Several analytical approaches were used to provide evidence that DDG was grafted onto chitosan. Compared to unmodified chitosan, DDG-modified chitosan had significantly increased absorbance in the UV-visible region, and in the C-H and carbonyl-stretching regions of the IR spectra. Also, the 1H NMR spectrum of a soluble fraction of DDG-chitosan had broad peaks near 1.2 ppm consistent with the grafting of DDG onto the polymer. Additional evidence for DDG grafting was obtained in two studies in which the DDG-modified chitosan was subjected to nitrous acid hydrolysis. First, a highly modified and insoluble DDG-chitosan was suspended in 10% acetic acid. After partial hydrolysis, peaks associated with the sugar and dodecyl gallate moieties were observed to appear in the solution phase 1H NMR spectrum. Finally, the DDG-modified chitosan was hydrolyzed and fractions were separated by HPLC. One fraction showing both UV absorbance (characteristic of the phenolic) and carbohydrate reactivity to anthrone was purified by two chromatographic steps. This fraction was analyzed by both FAB-MS and electrospray-MS, and observed to have a molecular weight of 371 Da. These results provide evidence that peroxidases can be used to graft phenolic moieties onto the polysaccharide chitosan.

Lauryl gallate inhibits the activity of protein tyrosine kinase c-Src purified from human platelets.

The inhibitory effect of gallic acid (3,4,5-trihydroxybenzoic acid), and its ester derivatives methyl, propyl, octyl and lauryl has been tested on the tyrosine kinase activity of affinity purified c-Src from human platelets, using the artificial substrate Poly (Glu,Na,Tyr) 4:1. When tested as inhibitor of the autophosphorylation of the enzyme and the phosphorylation of the protein tyrosine phosphatase SHP-1 by c-Src, lauryl gallate was found to be a more potent inhibitor than other widely used protein tyrosine kinase (PTK) inhibitors such as genistein and herbimycin A. However, lauryl gallate did not inhibit the activity of the serine threonine kinases protein kinase A (PKA) and casein kinase II (CKII) from rat brain.

Polyhydroxybenzoates Inhibit Ascorbic Acid Activation of Mitochondrial Glycerol-3-phosphate Dehydrogenase: IMPLICATIONS FOR GLUCOSE METABOLISM AND INSULIN SECRETION

Glycerol-3-phosphate dehydrogenase from pig brain mitochondria was stimulated 2.2-fold by the addition of 50 microm l-ascorbic acid. Enzyme activity, dependent upon the presence of l-ascorbic acid, was inhibited by lauryl gallate, propyl gallate, protocatechuic acid ethyl ester, and salicylhydroxamic acid. Homogeneous pig brain mitochondrial glycerol-3-phosphate dehydrogenase was activated by either 150 microm L-ascorbic acid (56%) or 300 microm iron (Fe(2+) or Fe(3+) (62%)) and 2.6-fold by the addition of both L-ascorbic acid and iron. The addition of L-ascorbic acid and iron resulted in a significant increase of k(cat) from 21.1 to 64.1 s(-1), without significantly increasing the K(m) of L-glycerol-3-phosphate (10.0-14.5 mm). The activation of pure glycerol-3-phosphate dehydrogenase by either L-ascorbic acid or iron or its combination could be totally inhibited by 200 microm propyl gallate. The metabolism of [5-(3)H]glucose and the glucose-stimulated insulin secretion from rat insulinoma cells, INS-1, were effectively inhibited by 500 microm or 1 mm propyl gallate and to a lesser extent by 5 mm aminooxyacetate, a potent malate-aspartate shuttle inhibitor. The combined data support the conclusion that l-ascorbic acid is a physiological activator of mitochondrial glycerol-3-phosphate dehydrogenase, that the enzyme is potently inhibited by agents that specifically inhibit certain classes of di-iron metalloenzymes, and that the enzyme is chiefly responsible for the proximal signal events in INS-1 cell glucose-stimulated insulin release.

Mechanistic Aspects of the Induction of Apoptosis by Lauryl Gallate in the Murine B-Cell Lymphoma Line Wehi 231

The effect of lauryl gallate (antioxidant E-312) has been studied on the mouse B-cell lymphoma line Wehi 231. This compound is able to inhibit protein tyrosine kinases (PTKs) in whole cells and in crude extracts with a better efficiency than other well-known PTK inhibitors such as herbimycin or genistein. Initial events triggered upon the incubation of cells with lauryl gallate in phosphate-buffered saline (up to 1 h) include the inhibition of tyrosine phosphorylation, discharge of the mitochondrial transmembrane potential, and induction of mRNA for Bcl-2. Long-term cultures in complete medium supplemented with fetal calf serum (up to 24 h) in the presence of this compound exhibit clear apoptotic features such as increase in phosphatidylserine in the cell surface, decrease in the functionality of mitochondria, cytochrome c release to the cytosol, activation of caspases, hypodiploidy, and oligonucleosomal breakdown of DNA. Comparison between Wehi cells overexpressing Bcl-2 (Wehi-bcl-2) with Wehi-neo cells shows a delay in the manifestations of the apoptotic signs, indicating that Bcl-2 has a partial protective effect on the apoptosis induced by lauryl gallate. The proapoptotic effect of lauryl gallate is not dependent on DNA or protein synthesis, is not blocked by the chelation of calcium, and is not reverted by N-acetylcysteine.

DETERMINATION OF ADDITIVES IN COSMETICS BY MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY

A micellar electrokinetic capillary chromatography (MECC) method suitable for the determination of antioxidants and preservatives permitted in cosmetic products is described. Unlike reversed phase high performance liquid chromatography (HPLC) this method simultaneously separates ionic solutes (sorbic acid and benzoic acid) and non-polar components (butylated hydroxytoluene and dodecyl gallate). A buffer consisting of 15 mM sodium dodecyl sulfate, 35 mM sodium cholate, 10 mM boric acid, and 10 mM sodium tetraborate adjusted to pH 9.5 and an 80 cm (total length) bare fused silica column gave good separations. The determination of additives in some cosmetic products was performed using both MECC and HPLC. There was good agreement between the methods.

Amperometric pH-sensing biosensors for urea, penicillin, and oxalacetate

The possibility of constructing a biosensor exploiting amperometric pH-sensing was investigated. The principle is based on the use of pH-sensitive redox-active probe molecules. The selected probe molecules applied in various forms, e.g. dissolved hematein, electrode bulk lauryl gallate, adsorbed methylene blue poly( o-phenylenediamine) film, were used for the construction of penicillin (with penicillinase), urea (with urease), and oxalacetate (with oxalacetate decarboxylase) biosensors. Platinum, gold and solid composite electrodes were used as transducers. The biosensors exhibited low detection limits, from 2 to 10 μM, linear responses up to 2 mM, insensitivity to a small variation in the ion concentrations, a good accuracy and storage stability. The present, new concept could extend the range of analytes detectable using the amperometric transduction technology, such as substrates of decarboxylases, amidohydrolases, esterases and other hydrolases.

Separation and Determination of Phenolic Antioxidants by HPLC with Surfactant/n-Propanol Mobile Phases

The influence of cationic and anionic surfactants and short-chain alcohols in the mobile phase on the retention of five antioxidants has been studied. The solutes chosen were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and propyl, octyl, and dodecyl gallates (PG, OG, DG).The surfactants were hexadecyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), and n-propanol (PrOH) was the selected alcohol. A simple isocratic reversed-phase method for the antioxidant determination is proposed. Separation of five primary antioxidants takes 18 min with the mobile phase SDS 0.10 M/H 3 PO 4 0.01 M/PrOH 30%. Variation of the percentage of alcohol in the mobile phase permits optimization of the retention times of the antioxidants. Detection limits in the pg range were obtained for the all solutes. The method was used to determine the antioxidants in olive oil at three different levels, giving mean recoveries close to 100% for all the solutes (BHA 102%, PG 99%, OG 99%, DG 99%) except BHT (84%).

Potent and Selective Inhibition of Squalene Epoxidase by Synthetic Galloyl Esters

n-Alkyl esters (ethyl, octyl, dodecyl, and cetyl) of gallic acid were evaluated as enzyme inhibitors of recombinant rat squalene epoxidase (SE), a rate-limiting enzyme of cholesterol biogenesis. Dodecyl (6) (IC50 = 0.061 μM) showed the most potent inhibition, which was far more potent than those of previously reported naturally occurring gallocatechins. Octyl gallate (5) (IC50 = 0.83 μM) and cetyl gallate (7) (IC50 = 0.59 μM) also showed good inhibition, while gallic acid (IC50 = 73 μM) itself was not so active. In addition, chemically synthesized galloyl ester of cholesterol (9) (IC50 = 3.9 μM), farnesol derivative (10) (IC50 = 0.57 μM), and dodecyl galloyl amide (8) (IC50 = 3.0 μM) were also potent inhibitors of SE. Inhibition kinetics revealed that dodecyl gallate inhibited SE in competitive (KI = 0.033 μM) and no-time-dependent manner. The potent inhibition of the flavin monooxygenase would be caused by specific binding to the enzyme, and by scavenging reactive oxygen species required for the epoxidation reaction.

Apoptosis-Inducing Activity of Lipid Derivatives of Gallic Acid.

Gallic acid derivatives with a lipophilic group (hydrogenated farnesyl gallate, lauryl gallate, gallic acid laurylamide and cholesteryl gallate) were examined for their ability to induce apoptosis in human monoblastic leukemia U937 cells. Farnesyl ester derivative is the most potent apoptosis inducer among the compounds examined. The results suggest that lipid derivatives can augment the apoptosis-inducing activity of gallic acid depending on the structure. These findings will provide useful information in developing anti-cancer agents.

Determination of synthetic antioxidants in dairy products and dietetic supplements by micellar liquid chromatography with direct sample injection

A simple and rapid HPLC method for the determination of synthetic antioxidants (propyl gallate, tert-butylhydroquinone, 2,4,5-trihydroxybutyrophenone, nordihydroguaiaretic acid, octyl gallate, 3-tert-butyl-4-hydroxyanisole and dodecyl gallate) in powdered and liquid milk, cream of milk and dietetic supplements is described. The samples are diluted or solved in a micellar solution, filtered and directly injected. The retention behavior of the antioxidants on a C18 column, with micellar mobile phases containing SDS (0.05–0.15 M), n-propanol (1–9%, v/v) and 10 mM phosphate at pH 3, has been studied by using mathematical models. Retention is predicted with errors below 3%. To optimize the mobile phase composition, a procedure which takes into account the position and shape of the peaks is applied. The optimized mobile phase, which contains 0.090 M SDS and 6.6% n-propanol, allows the separation of six antioxidants in less than 13 min. Calibration curves are linear (r>0.9998) and the limits of detection range from 0.05 to 0.3 ng antioxidant, which correspond to concentrations well below the levels allowed in foods. Repeatabilities for standards containing 5 μg mL−1 ranged from 0.2 to 1.6%.

Quantification of synthetic phenolic antioxidants in liver pâtés

Pâtés are products with high fat levels and their consumption has increased in Portugal over the past few years. Owing to their composition, lipid oxidation is one of the primary mechanisms associated with deterioration of their quality. Therefore, antioxidants have become a useful group of food additives because they help to maintain the organoleptic quality of pâtés by avoiding rancidity. The aim of this work was the evaluation of seven synthetic antioxidants with phenolic structure, namely, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butyl hydroquinone (TBHQ), propyl (PG), octyl (OG) and dodecyl gallates (DG) and nordihydroguaiaretic acid (NDG), in liver pâtés available on the Portuguese retail market. The high performance liquid chromatography (HPLC) procedure described in AOAC for oils and fats was found to be inappropriate for pâtés, probably owing to their complex matrices. A modification of the Association of Official Analytical Chemists (AOAC) extraction procedure is thus presented. Extensive validation of this extraction procedure was carried out by recovery tests. Over 91% recoveries of added antioxidants were observed, except for PG and OG whose recoveries were 78.0±2.2 and 82.1±1.1 1%, respectively. The precision found was below 3.8%. No synthetic antioxidants were detected in six of the 12 assayed brands. One sample contained BHA and five samples contained NDG (concentrations ranged from trace levels to 26.3±0.0 mg/kg of product). When pepper corn was added as an additive to pâtés, piperine (the main compound of pepper) appeared on the chromatogram but it did not interfere with the evaluation of the other antioxidants.

Simultaneous determination of antioxidants, preservatives and sweeteners permitted as additives in food by mixed micellar electrokinetic chromatography

A micellar electrokinetic chromatography method was developed to simultaneously analyse commonly used food additives. The additive mixture, comprising propyl gallate, octyl gallate, dodecyl gallate, butylated hydroxyanisole, butylated hydroxytoluene, tertiary butylhydroquinone, p-hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid ethyl ester, benzoic acid, sorbic acid, saccharin, aspartame and acesulfame-K, was not resolved using single surfactant micellar systems consisting of sodium dodecyl sulfate (SDS), sodium cholate (SC) or sodium deoxycholate (SDC). The separation of these additives using mixed micellar systems, involving SDS/SC, SDS/SDC and SC/SDC, was investigated. Organic solvents were added to the mixed micellar phases to optimise the separation. The mixture was successfully separated using a 20 m M borate buffer with 35 m M SC, 15 m M SDS and 10% methanol added at pH 9.3. Additives in cola beverages and low-joule jam were investigated and quantified using this method.

Antioxidants reversibly inhibit the spontaneous resumption of meiosis.

We previously showed that the cell-permeant antioxidant 2(3)-tert-butyl-4-hydroxyanisole (BHA) inhibited germinal vesicle breakdown (GVBD) in oocyte-cumulus complexes (OCC) of the rat. The objective of the present studies was to assess other antioxidants and whether such inhibition was reversible. Spontaneous GVBD in OCC incubated for 2 h was significantly inhibited (P < 0.005) by nordihydroguaiaretic acid (NDGA; GVBD = 19.4%), BHA (GVBD = 25.7%), octyl gallate (OG; GVBD = 52.2%), ethoxyquin (EQ; GVBD = 58.8%), 2, 6-di-tert-butyl-hydroxymethyl phenol (TBHMP; GVBD = 59%), butylated hydroxytoluene (BHT; GVBD = 59.5%), and tert-butyl hydroperoxide (TBHP; GVBD = 60.0%). Other antioxidants that produced lower but significant (P < 0.05) inhibition of oocyte maturation included propyl gallate (PG; GVBD = 70.3%), 2,4,5-trihydroxybutrophenone (THBP; GVBD = 71.4%), and lauryl gallate (LG; GVBD = 71.4%). Antioxidants that had no effect on oocyte maturation at the same concentration (100 microM) included ascorbic acid, vitamin E, and Trolox. Inhibition of GVBD was evident for up to 8 h of incubation of OCC and denuded oocytes (DO) with BHA or NDGA and was reversed by washing. NDGA was less potent than BHA for inhibition of GVBD in DO, unlike that seen with OCC. Oocyte maturation was induced by incubation of follicles for 3 h with human chorionic gonadotropin (hCG), and this response was inhibited by BHA or NDGA. These findings support the conclusion that cell-permeant antioxidants inhibit spontaneous resumption of meiosis, which may implicate a role of oxygen radicals in oocyte maturation.