Abstract: Oxidative stress, a result of an overproduction and accumulation of free radicals, is the leading cause of several degenerative diseases such as cancer, atherosclerosis, cardiovascular diseases, ageing and inflammatory diseases. Polyphenols form an important class of naturally occurring antioxidants, having innumerable biological activities such as anticancer, antifungal, antibacterial, antiviral, antiulcer and anticholesterol, to name a few. Among various polyphenols, gallic acid (3,4,5-trihydroxybenzoic acid), a naturally occurring low molecular weight triphenolic compound, has emerged as a strong antioxidant and an efficient apoptosis inducing agent. Starting from the bioavailability and the biosynthetic pathway of gallic acid, this review includes various in vitro, in vivo and in silico studies providing the mode of action, radical scavenging activity, ability to inhibit lipid peroxidation, maintenance of endogenous defense systems and metal ion chelation by this triphenolic molecule, along with a comprehensive overview of factors responsible for its high antioxidant activity. Gallic acid derivatives have also been found in a number of phytomedicines with diverse biological and pharmacological activities, including radical scavenging, interfering with the cell signaling pathways and apoptosis of cancer cells. The diverse range of applications of this simple polyphenol is due to a fine amalgam between its antioxidant and prooxidant potential. The existing literature on this dual behavior of gallic acid and its derivatives is reviewed here. This is followed by an account of their potential clinical and industrial applications.

Abstract: BACKGROUND Total phenolic content (TPC) and antioxidant activity (AA) assays in microplates save resources and time, therefore they can be useful to overcome the fact that the conventional methods are time-consuming, labour intensive and use large amounts of reagents. An intra-laboratory validation of the Folin–Ciocalteu microplate method to measure TPC and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) microplate method to measure AA was performed and compared with conventional spectrophotometric methods. RESULTS To compare the TPC methods, the confidence intervals of a linear regression were used. In the range of 10–70 mg L−1 of gallic acid equivalents (GAE), both methods were equivalent. To compare the AA methodologies, the F-test and t-test were used in a range from 220 to 320 µmol L−1 of Trolox equivalents. Both methods had homogeneous variances, and the means were not significantively different. The limits of detection and quantification for the TPC microplate method were 0.74 and 2.24 mg L−1 GAE and for the DPPH 12.07 and 36.58 µmol L−1 of Trolox equivalents. The relative standard deviation of the repeatability and reproducibility for both microplate methods were ≤6.1%. The accuracy ranged from 88% to 100%. CONCLUSION The microplate and the conventional methods are equals in a 95% confidence level. © 2014 Society of Chemical Industry

Abstract: The effectiveness of chitosan fruit coating to delay the qualitative and nutraceutical traits of three strawberry cultivars, namely "Candonga", "Jonica" and "Sabrina", as well as the effects of chitosan on antioxidant enzymes were evaluated. The fruits were coated with 1% and 2% chitosan solution and stored at 2 °C for nine days. Samples were taken every three days. Physico-chemical (weight loss, soluble solid content and titratable acidity) and nutraceutical (total polyphenol, anthocyanin, flavonoid, ascorbic acid content and antioxidant capacity) properties along with the enzymatic activity (catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO), guaiacol peroxidase (GPX) and lipoxygenase (LOX)) were evaluated. Chitosan treatment significantly reduced water loss and delayed the qualitative changes in color, titratable acidity and ascorbic acid content in dose- and cultivar-dependent manners. Additionally, changes in the total polyphenol, anthocyanin and flavonoid contents and the antioxidant capacity of chitosan-coated strawberry fruits were delayed. Chitosan coating enhanced the activity of some antioxidant enzymes, preventing flesh browning and reducing membrane damage. A global view of the responses of the three strawberry cultivars to chitosan coating and storage temperature was obtained using principal component analysis. Chitosan-coated fruit exhibited a slower rate of deterioration, compared to uncoated fruit in all tested cultivars.

Abstract: This study was carried out to evaluate the phytochemical constituents and antioxidant potential of the leaves and flowers extracts of Halimium halimifolium in order to validate the medicinal potential of this herb. The antioxidant activity of alcoholic and aqueous extracts was evaluated using 2, 2-diphenyl-l-picrylhydrazyl (DPPH), 2, 2’-azinobis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) assays. The total polyphenol, flavonoid and tannincontent were determined according respectively to Folin-Ciocalteu method, Zhishen method and Broadhurst method. The leaves of H. halimifolium had greater antioxidant activity than flowers by DPPH and ABTS assays. The ethanol extract of the leaves exhibited the better antioxidant activity by DPPH assay (IC50 = 1.19 µg.mL-1), the n-butanol by ABTS assays (IC50 = 1.73µg.mL-1). As opposed to FRAP method the flowers had greater antioxidant activity as leaves. Ethyl acetate extract exhibited better antioxidant activity (IC50 = 15.5 mmol Fe2+.g-1). The obtained results showed that the extracting solvent significantly influenced the antioxidant property estimations of Halimium halimifolium. The ethanol is a recommended solvent for extracting antioxidants from this plant. The antioxidant activity determined by DPPH, ABTS and FRAP demonstrated a linear relationship with their polyphenols, flavonoids and tannins content.

Abstract: Bee pollen constitutes a natural source of antioxidants such as phenolic acids and flavonoids, which are responsible for its biological activity. Research has indicated the correlation between dietary polyphenols and cardioprotective, hepatoprotective, anti-inflammatory, antibacterial, anticancerogenic, immunostimulating, antianaemic effects, as well as their beneficial influence on osseous tissue. The beneficial effects of bee pollen on health result from the presence of phenolic acids and flavonoids which possess anti-inflammatory properties, phytosterol and linolenic acid which play an anticancerogenic role, and polysaccharides which stimulate immunological activity. Polyphenols are absorbed in the alimentary tract, metabolised by CYP450 enzymes, and excreted with urine and faeces. Flavonoids and phenolic acids are characterised by high antioxidative potential, which is closely related to their chemical structure. The high antioxidant potential of phenolic acids is due to the presence and location of hydroxyl groups, a carboxyl group in the immediate vicinity of ortho-diphenolic substituents, and the ethylene group between the phenyl ring and the carboxyl group. As regards flavonoids, essential structural elements are hydroxyl groups at the C5 and C7 positions in the A ring, and at the C3′ and C4′ positions in the B ring, and a hydroxyl group at the C3 position in the C ring. Furthermore, both, the double bond between C2 and C3, and a ketone group at the C4 position in the C ring enhance the antioxidative potential of these compounds. Polyphenols have an ideal chemical structure for scavenging free radicals and for creating chelates with metal ions, which makes them effective antioxidants in vivo.

Abstract: Beneficial effects of green tea (Camellia sinensis, Theaceae) extracts against obesity have been reported; however, the anti-obesity ability of the major components of green tea, polysaccharides, polyphenols and caffeine is not clear. Therefore, experiments with total green tea extracts, polyphenols, polysaccharides, caffeine, and a complex of polysaccharide and polyphenol at a dose of 400 or 800 mg kg⁻¹ were conducted on high-fat diet fed rats for 6 weeks to investigate their anti-obesity effects. The results indicated that polyphenols and polysaccharides were responsible for the suppressive effect of green tea extracts on body weight increase and fat accumulation. Moreover, polyphenols, polysaccharides, or caffeine can improve blood lipid and antioxidant levels, and effectively reduce rat serum leptin levels, inhibit the absorption of fatty acids, and markedly reduce the expression levels of the IL-6 and TNF-α gene. Furthermore, it was shown that polysaccharides and polyphenols were synergistic in reduction of serum leptin levels and in anti-inflammatory activity. These results suggest that the polysaccharide combination with polyphenols might be a potential therapy against obesity.

Abstract: BACKGROUND Various studies have been conducted to evaluate the effect of phenolic compounds on production animals. Supplementation of animal diets with phytogenic compounds, such as different essential oils and polyphenols, could improve animal productivity as well as the chemical composition and oxidative stability of food derived from those animals. RESULTS During the trial, 80 male broilers of the Ross 308 strain were allocated to four dietary groups: control and three groups supplemented with thymol, tannic acid and gallic acid. Feed utilisation was improved in all experimental groups and tannic acid also improved final body weight. Gallic acid significantly increased n-3 long-chain polyunsaturated fatty acids. A hypocholesterolaemic effect was noticed in all groups in liver, but not in muscle. The glucose lowering effect in serum was noticed in the tannic acid group in comparison to other experimental groups. Oxidative susceptibility was improved by tannic acid in liver and breast and by gallic acid in breast muscle. CONCLUSION The inclusion of phenolic compounds enhanced growth performance, decreased lipid oxidation, decreased cholesterol value and increased beneficial fatty acids content. Positive effects varied depending on phenolic compound used and, therefore, it would be interesting to further investigate synergistic effects of investigated phenolic compound. © 2014 Society of Chemical Industry

Abstract: Polyphenols form the largest group of compounds among natural antioxidants, which largely affect the overall antioxidant and anti-free radical activity of cocoa beans. The qualitative and quantitative composition of individual fractions of polyphenolic compounds, even within one species, is very diverse and depends on many factors, mainly on the area of cocoa trees cultivation, bean maturity, climatic conditions during growth, and the harvest season and storage time after harvest. Thermal processing of cocoa beans and cocoa derivative products at relatively high temperatures may in addition to favorable physicochemical, microbiological, and organoleptic changes result in a decrease of polyphenols concentration. Technological processing of cocoa beans negatively affects the content of polyphenolic compounds.

Abstract: Pomegranates are one of the main highly valuable sources of ellagitannins Despite the potential health benefits of these compounds, reliable data on their content in pomegranates and derived extracts and food products is lacking, as it is usually underestimated due to their complexity, diversity, and lack of commercially available standards This study describes a new method for the analysis of the extractable and nonextractable ellagitannins based on the quantification of the acid hydrolysis products that include ellagic acid, gallic acid, sanguisorbic acid dilactone, valoneic acid dilactone, and gallagic acid dilactone in pomegranate samples The study also shows the occurrence of ellagitannin C-glycosides in pomegranates The method was optimized using a pomegranate peel extract To quantify nonextractable ellagitannins, freeze-dried pomegranate fruit samples were directly hydrolyzed with 4 M HCl in water at 90 °C for 24 h followed by extraction of the pellet with dimethyl sulfoxide/methanol (50:50, v/v) The method was validated and reproducibility was assessed by means of an interlaboratory trial, showing high reproducibility across six laboratories with relative standard deviations below 15% Their applicability was demonstrated in several pomegranate extracts, different parts of pomegranate fruit (husk, peels, and mesocarp), and commercial juices A large variability has been found in the ellagitannin content (150-750 mg of hydrolysis products/g) and type (gallagic acid/ellagic acid ratios between 4 and 015) of the 11 pomegranate extracts studied

Abstract: Excessive production of free radicals causes direct damage to biological molecules such as DNA, proteins, lipids, carbohydrates leading to tumor development and progression. Natural antioxidant molecules from phytochemicals of plant origin may directly inhibit either their production or limit their propagation or destroy them to protect the system. In the present study, Monodora myristica a non-timber forest product consumed in Cameroon as spice was screened for its free radical scavenging properties, antioxidant and enzymes protective activities. Its phenolic compound profile was also realized by HPLC. This study demonstrated that M. myristica has scavenging properties against DPPH•, OH•, NO•, and ABTS• radicals which vary in a dose depending manner. It also showed an antioxidant potential that was comparable with that of Butylated Hydroxytoluene (BHT) and vitamin C used as standard. The aqueous ethanol extract of M. myristica barks (AEH); showed a significantly higher content in polyphenolic compounds (21.44 ± 0.24 mg caffeic acid/g dried extract) and flavonoid (5.69 ± 0.07 quercetin equivalent mg/g of dried weight) as compared to the other studied extracts. The HPLC analysis of the barks and leaves revealed the presence of several polyphenols. The acids (3,4-OH-benzoic, caffeic, gallic, O- and P- coumaric, syringic, vanillic), alcohols (tyrosol and OH-tyrosol), theobromine, quercetin, rutin, catechine and apigenin were the identified and quantified polyphenols. All the tested extracts demonstrated a high protective potential on the superoxide dismutase (SOD), catalase and peroxidase activities. Finally, the different extracts from M. myristica and specifically the aqueous ethanol extract reveal several properties such as higher free radical scavenging properties, significant antioxidant capacities and protective potential effects on liver enzymes.

Abstract: Moringa oleifera Lam. is a fast-growing, tropical tree with various edible parts used as nutritious food and traditional medicine. This study describes an efficient preparatory strategy to extract and fractionate moringa leaves by fast centrifugal partition chromatography (FCPC) to produce polyphenol and isothiocyanate (ITC) rich fractions. Characterization and further purification of these fractions showed that moringa polyphenols were potent direct antioxidants assayed by oxygen radical absorbance capacity (ORAC), whereas moringa ITCs were effective indirect antioxidants assayed by induction of NAD(P)H quinone oxidoreductase 1 (NQO1) activity in Hepa1c1c7 cells. In addition, purified 4-[(α-l-rhamnosyloxy)benzyl]isothiocyanate and 4-[(4'-O-acetyl-α-l-rhamnosyloxy)benzyl]isothiocyanate were further evaluated for their ORAC and NQO1 inducer potency in comparison with sulforaphane (SF). Both ITCs were as potent as SF in inducing NQO1 activity. These findings suggest that moringa leaves contain a potent mixture of direct and indirect antioxidants that can explain its various health-promoting effects.

Abstract: Agricultural residues like sugarcane bagasse (SCB), corn husk (CH), peanut husk (PNH), coffee cherry husk (CCH), rice bran (RB) and wheat bran (WB) are low-value byproducts of agriculture. They have been shown to contain significant levels of phenolic compounds with demonstrated antioxidant properties. In this study, the effects of two types of solvent extraction methods: solid–liquid extraction (SLE) and hot water extraction on the recovery of phenolic compounds from agricultural residues were investigated to optimize the extraction conditions based on total phenolic content (TPC), total tannin content (TTC) and total flavonoids content (TFC). Methanol (50 %) was found to be the most efficient solvent for the extraction of phenolics with higher DPPH, nitric oxide radical scavenging and reducing power activity, followed by ethanol and water. The phenolic compounds of methanolic extracts (50 %) were determined by reverse phase high performance liquid chromatography; in addition gallic acid became the major phenolic acid present in all the agricultural residues whereas ferulic acid, epicatechin, catechin, quercitin and kampferol present in lesser amounts. The present investigation suggested that agricultural residues are potent antioxidants. The overall results of this research demonstrated the potential of agricultural residues to be an abundant source of natural antioxidants suitable for further development into dietary supplements and various food additives.