Main antimicrobial compounds in table olives

The inhibitors involved in the lactic acid fermentation of table olives were investigated in aseptic olive brines of the Manzanilla and Gordal varieties. Phenolic and oleosidic compounds in these brines were identified by high-performance liquid chromatography with ultraviolet and electrospray ionization mass spectrometry detection, and several substances were also characterized by nuclear magnetic resonance. Among these compounds, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol showed the strongest antilactic acid bacteria activity, and its presence in brines could explain the growth inhibition of these microorganisms during olive fermentation. However, it was found that the dialdehydic form of decarboxymethyl elenolic acid, identified for the first time in table olives, and an isomer of oleoside 11-methyl ester were also effective against Lactobacillus pentosus and can, therefore, contribute to the antimicrobial activity of olive brines. It must also be stressed that the three new inhibitors discovered in table olive brines exerted a more potent antibacterial activity than the well-studied oleuropein and hydroxytyrosol.     

New phenolic compounds and antioxidant potential of Catharanthus roseus

Screening of the phenolic compounds from seeds, stems, leaves and petals of Catharanthus roseus (L.) G. Don (cv. Little Bright Eye) was achieved by HPLC-DAD-ESI-MS/MS. This is the first detailed study of noncolored phenolics in C. roseus, which allowed the characterization of three caffeoylquinic acids and fifteen flavonol glycosides (di- and trisaccharides of kaempferol, quercetin and isorhamnetin). Fifteen compounds are reported for the first time in this species. The scavenging ability of the different plant matrices was assessed against DPPH(*) radical and against reactive oxygen (superoxide radical) and a reactive nitrogen (nitric oxide) species. A concentration-dependent protective effect was observed for seeds and tissues, with petals shown to be the most active.     

Evolution of phenolic compounds and antioxidant activity during malting

Two barley varieties, Gan4 and Hamelin, were malted to investigate the evolution of phenolic compounds and antioxidant activity during malting. The antioxidant activity was evaluated with DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, and metal chelating activity. Results showed that malting had significant influences on individual and total phenolic contents as well as antioxidant activities of two barley varieties. The contents of some phenolic compounds and the antioxidant activities decreased significantly during steeping and the early stages of germination and then increased remarkably during the later stages of germination and subsequent kilning. The most phenolic compounds identified in barley were (+)-catechin and ferulic acid, which both changed significantly during malting. Moreover, results from the Pearson correlation analysis showed that there were good correlations among DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, total phenolic content and sum of individual phenolic contents during malting.     

RP-HPLC analysis of the phenolic compounds of plant extracts. investigation of their antioxidant capacity and antimicrobial activity

Extracts of aromatic plants of Greek origin were examined as potential sources of phenolic compounds. RP-HPLC with UV detection was employed for the identification and quantification of the phenolic antioxidants, present in methanolic extracts. The most abundant phenolic acids were ferulic acid (1.1-280 mg/100 g of dry sample) and caffeic acid (1.2-60 mg/100 g of dry sample). (+)-Catechin and quercetin were the most abundant flavonoids. Apigenin and luteolin were detected in high amounts in Menta pulegium and Thymus vulgaris, respectively. The antioxidant capacity was determined, in dried ground plants and in their methanol extracts, with the Rancimat test using sunflower oil as substrate. Both pulverized plants and extracts showed antioxidant capacity. Total phenolic content in the extracts was determined spectrometrically according to the Folin-Ciocalteu assay and ranged from 1 to 21 mg of gallic acid/100 g of dry sample. Antimicrobial activity of the extracts against selected microbes was also conducted in this study.     

Relationship between phenolic compounds, anthocyanins content and antioxidant activity in colored barley germplasm

Barley and its products are good sources of antioxidants. This experiment was conducted to examine the classification and concentration of phenolic compounds, proanthocyanidins, and anthocyanins in 127 lines of colored barley. Their relationship with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was also examined. Barley was placed into seven groups using the colorimeter: hulled (black 1, black 2, black 3, and purple) and unhulled (black, blue, and purple). The contents of phenolic compounds and anthocyanins were analyzed by using HPLC. The average content of phenolic compounds in unhulled barley groups (268.6 microg/g) was higher than that in hulled (207.0 microg/g) (P > 0.05). The proanthocyanidins content was determined by modified vanillin assay. The average content of proanthocyanidins was significantly higher in purple and blue barley groups compared with black (P < 0.05). The content of anthocyanins varied from 13.0 to 1037.8 microg/g. Purple and blue barley groups contained higher average contents of anthocyanins than black (P < 0.05). The most common anthocyanin in the purple barley groups was cyanidin 3-glucoside, whereas delphinidin 3-glucoside was the most abundant anthocyanin in the blue and black groups. In colored barley, DPPH radical scavenging activity had high positive correlation to the content of phenolic compounds and proanthocyanidins.     

Composition of phenolic compounds and antioxidant activity of commercial aqueous smoke flavorings

The antioxidant activity of 12 aqueous commercial smoke flavorings used in the food industry was determined by two methods: bleaching of the carotenoid crocin and scavenging of the DPPH radical. The reaction with the DPPH radical was evaluated by calculating the effective concentration (EC50) and the antiradical efficiency (AE). A gas chromatography-mass spectrometry method was, moreover, used for the determination of 2-methoxyphenols, 2,6-dimethoxyphenols, and dihydroxybenzenes. The methoxyphenols were extracted from the aqueous smoke by dichloromethane, and also the residue aqueous phase was analyzed to determine the more water-soluble dihydroxybenzenes. The recovery and the repeatability of the method are reported. The total phenolic concentrations of the smoke flavorings showed a wide range, from about 1000 to 25000 mg/kg. Considering the three classes of compounds, the concentrations were about 300-3000 mg/kg for the 2-methoxyphenols, 200-11000 mg/kg for the 2,6-dimethoxyphenols, and 140-10000 mg/kg for the dihydroxybenzenes. The range of the antioxidant activities of the smoke flavorings was wide, reflecting the wide range of the phenolic concentrations. Good correlations were obtained between the total phenolic concentration and the antioxidant activities determined by both the DPPH and crocin assays.     

Phenolic, polysaccharidic, and lipidic fractions of mushrooms from northeastern Portugal: chemical compounds with antioxidant properties

Mushrooms do not constitute a significant portion of the human diet, but their consumption continues to increase due to their functional benefits and presence of bioactive compounds. Some of those compounds can be found in the phenolic, polysaccharidic, and lipidic fractions of edible and inedible species. Herein, those fractions of five wild mushrooms (Coprinopsis atramentaria, Lactarius bertillonii, Lactarius vellereus, Rhodotus palmatus, and Xerocomus chrysenteron) from northeastern Portugal were studied for their chemical composition and antioxidant properties. Protocatechuic, p-hydroxybenzoic, p-coumaric, and cinnamic acids were found in the phenolic fraction; rhamnose, xylose, fucose, arabinose, fructose, glucose, manose, mannitol, sucrose, maltose, and trehalose were quantified in polysaccharidic fraction; and linoleic and stearic (only in Lactarius sp.) acids, and β- and γ-tocopherols were the main compounds in the lipidic fraction. C. atramentaria and X. chrysenteron phenolic fractions gave the highest free radical scavenging activity, reducing properties, and lipid peroxidation inhibition in brain homogenates, which is in agreement with its highest content in total phenolics. Furthermore, among the polysaccharidic fractions C. atramentaria also gave the highest antioxidant activity, which is in agreement with its highest total polysaccharides content and sugars obtained after hydrolysis.     

Bioaccessibility and antioxidant activity stability of phenolic compounds from extra-virgin olive oils during in vitro digestion

The impact of an in vitro procedure that mimics the physiochemical changes occurring in gastric and small intestinal digestion on the bioaccessibility and antioxidant activity of phenols from 10 extra-virgin olive oil samples was assessed. Extra-virgin olive oil phenols were totally extracted in the aqueous phase, which reproduces gastric fluids during the digestion procedure. A linear bioaccessibility model, based on tyrosol behavior in model oil samples, was used to estimate the bioaccessibility index (BI%) of extra-virgin olive oil phenols. The BI% varied amongst samples from a maximum of 90% to a minimum of 37%, thus indicating that only a fraction of phenols can be considered bioaccessible. The specific antioxidant activity of olive oil phenols proved to be negatively affected by the digestion procedure. By computing a principal component analysis, it was possible to show that differences in the potential bioactive effect of extra-virgin olive oil samples were related to different phenolic profiles.     

Factors influencing phenolic compounds in table olives (Olea europaea)

The Mediterranean diet appears to be associated with a reduced risk of several chronic diseases including cancer and cardiovascular and Alzheimer's diseases. Olive products (mainly olive oil and table olives) are important components of the Mediterranean diet. Olives contain a range of phenolic compounds; these natural antioxidants may contribute to the prevention of these chronic conditions. Consequently, the consumption of table olives and olive oil continues to increase worldwide by health-conscious consumers. There are numerous factors that can affect the phenolics in table olives including the cultivar, degree of ripening, and, importantly, the methods used for curing and processing table olives. The predominant phenolic compound found in fresh olive is the bitter secoiridoid oleuropein. Table olive processing decreases levels of oleuropein with concomitant increases in the hydrolysis products hydroxytyrosol and tyrosol. Many of the health benefits reported for olives are thought to be associated with the levels of hydroxytyrosol. Herein the pre- and post-harvest factors influencing the phenolics in olives, debittering methods, and health benefits of phenolics in table olives are reviewed.     

核桃酚类物质和蛋白间的相互作用及其抗氧化活性

酚类物质和蛋白质之间存在多种相互作用力,因此难以被充分提取。该研究以核桃蛋白为研究对象,用不同量的尿素和氯化钠定向破坏核桃酚类物质和核桃蛋白之间的离子键、氢键和疏水作用力,以研究核桃酚类物质和核桃蛋白之间的非共价键结合机制。结果显示在pH值3.0时,77.7%的酚类物质与蛋白以共价键结合,而有34.6%的缩合单宁与核桃蛋白以共价键结合。在pH值8.0时,有65.4%酚类物质和59.4%的缩合单宁与核桃蛋白以非共价键结合。其中疏水作用力是主要的非共价键结合方式。对以不同非共价键与核桃蛋白相结合的酚类物质的抗氧化活性进行测定,结果显示以离子键与蛋白结合的酚类物质的抗氧化活性最强。其中,在pH值3.0条件下与WPI（walnut protein isolates）以离子键结合的酚类物质的DPPH自由基清除能力为5.7%,Fe2+螯合率为5.9%,在pH值8.0条件下与WPI以离子键结合的酚类物质的DPPH自由基清除能力为10.9%, Fe2+螯合率为11.5%。另外,该研究还探讨了在pH值3.0和8.0时,70%(v/v)乙醇和60%(v/v)甲醇提取核桃蛋白中酚类物质的能力,结果表明这两种提取剂不能显著提高酚类物质的提取率,且不能有效得到具有较强抗氧化能力的酚类物质。     

Assessing antioxidant and prooxidant activities of phenolic compounds

Methods for determining primary antioxidant activity were evaluated. A beta-carotene bleaching method and a free radical method using 2, 2-diphenyl-1-picrylhydrazyl (DPPH(*)) were modified to rapidly test samples for potential antioxidant activity. Malonaldehyde production in a linoleic acid emulsion system assayed by an HPLC method was also used to determine antioxidant and prooxidant activities initiated by a metal catalyst (Cu(2+)). All methods were used to assess activity of selected phenolic compounds including several anthocyanidins/anthocyanins and selected berry extracts. Most phenolic compounds had prooxidant activity at low concentrations, unlike synthetic antioxidants (BHA and BHT). Compounds with similar structures exhibited comparable trends in antioxidant activity. Antioxidant activity usually increased with an increase in the number of hydroxyl groups and a decrease in glycosylation. The antioxidant activity of many phenolic compounds and extracts was comparable to those of synthetic antioxidants using the beta-carotene bleaching and HPLC methods.     

Low-density lipoprotein antioxidant activity of phenolic compounds and polyphenol oxidase activity in selected clingstone peach cultivars

The antioxidant potential of eight clingstone peach cultivars was investigated by determining phenolic compounds and inhibition of low-density lipoprotein (LDL) oxidation. Cultivars low in polyphenol oxidase (PPO) were also selected to minimize enzymatic browning. Inhibition of LDL oxidation varied from 17.0 to 37.1% in peach flesh extract, from 15.2 to 49.8% in whole peach extract, and from 18.2 to 48.1% in peel extract. Total phenols were 432.8-768.1 mg/kg in flesh extract, 483.3-803.0 mg/kg in whole extract, and 910.9-1922.9 mg/kg in peel extract. The correlation coefficient between relative LDL antioxidant activity and concentration of total phenols was 0.76. Peel PPO activity was higher than flesh activity in most cultivars. The lowest PPO and specific activities were found in the Walgant cultivar, followed by Kakamas and 18-8-23. These three cultivars combine the desirable characteristics of strong antioxidant activity, low PPO activity, and lower susceptibility to browning reactions.     

Chemical composition and antioxidant activity of phenolic compounds from wild and cultivated Sclerocarya birrea(Anacardiaceae) leaves

A quantitative study of the phenolic constituents of wild and cultivated leaves of Sclerocarya birrea(Anacardiaceae) was carried out by HPLC-UV/PDA and LC-MS. Phytochemical analysis of the methanol extract of wild plants led to the isolation of one new flavonol glycoside, quercetin 3-O-alpha-l-(5' '-galloyl)-arabinofuranoside (1), and eight known phenolic compounds; two epicatechin derivatives were also isolated from the same extract of the cultivated species. The antioxidant activity of all isolated compounds was determined by measuring free radical scavenging effects using the Trolox equivalent antioxidant capacity assay and the coupled oxidation of beta-carotene and linoleic acid (autoxidation assay).     

不同提取方式对萱草花中酚类物质及抗氧化活性的影响

为了研究超声、酶解-超声以及发酵-超声3种不同提取方式对萱草花中酚类物质的含量、组成形态及抗氧化活性的影响,以明黄、桔黄、桔红、朱红、大红5种颜色的萱草花为原料,检测不同萱草花中总黄酮和总多酚含量以及1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）和2,2'-联氮-双-3-乙基苯并噻唑啉-6-磺酸（2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid,ABTS）自由基清除率;利用高效液相色谱对游离态、共轭态和结合态3种形态酚类化合物进行测定,并研究其与抗氧化活性的关系。结果表明,不同颜色的萱草花中总黄酮和总多酚含量各不相同,其含量从高到低排列为：\     

Determination of total content of phenolic compounds and their antioxidant activity in vegetables--evaluation of spectrophotometric methods

This research studies in detail the contents of phenolic compounds determined by the Folin-Ciocalteu reagent and the antioxidant activities determined by the TEAC (Trolox equivalent antioxidant capacity), DPPH (using diphenyl-p-picrylhydrazyl radical), and FRAP (ferric reducing antioxidant power) methods, and their correlations for used standards with these methods (catechine, gallic acid, caffeic acid, ferulic acid, Trolox, ascorbic acid, and ferrous sulfate) and extracts from several species of commonly consumed vegetables were studied in detail. The comparison of absolute values of absorption coefficients for used standards and for individual methods allows one to choose optimal common standards for methods to be compared. The procedures applied for the same sets of the extracts using identical calibration procedures and common standards allowed better comparison of the results obtained by the TEAC, DPPH, and FRAP methods. The values of content of phenolic substances and total antioxidant activity of the sets of samples correlate very well for all used methods. The very high values of antioxidant activity were found in intensely colored vegetables (red cabbage, red onion, etc.), and the values were very low in watery vegetables such as potato, marrow, and cucumber.     

Effects of natural phenolic compounds on the antioxidant activity of lactoferrin in liposomes and oil-in-water emulsions

The effect of natural phenolic compounds on the antioxidant and prooxidant activity of lactoferrin was studied in liposomes and oil-in-water emulsions containing iron. The antioxidants tested with lactoferrin were alpha-tocopherol, ferulic acid, coumaric acid, tyrosol, and natural phenolic extracts obtained from three different extra-virgin olive oils and olive mill wastewater. The natural extracts of olive oils and mill wastewaters were composed mainly of polyphenols and simple phenolics, respectively. Lipid oxidation at 30 degrees C was determined by the formation of hydroperoxides and fluorescent compounds resulting from oxidized lipid interactions. All phenolic compounds showed synergistic properties in reinforcing the antioxidant activity of lactoferrin in lipid systems containing iron. The highest synergistic effects were observed for the phenolic extracts rich in polyphenols of extra-virgin olive oils and lactoferrin. This synergistic effect was higher in liposomes than in emulsions.     

Comparison of the concentrations of phenolic compounds in olive oils and other plant oils: correlation with antimicrobial activity

The antimicrobial activity of different edible vegetable oils was studied. In vitro results revealed that the oils from olive fruits had a strong bactericidal action against a broad spectrum of microorganisms, this effect being higher in general against Gram-positive than Gram-negative bacteria. Thus, olive oils showed bactericidal activity not only against harmful bacteria of the intestinal microbiota (Clostridium perfringens and Escherichia coli) also against beneficial microorganisms such as Lactobacillus acidophilus and Bifidobacterium bifidum. Otherwise, most of the foodborne pathogens tested (Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica, Yersinia sp., and Shigella sonnei) did not survive after 1 h of contact with olive oils. The dialdehydic form of decarboxymethyl oleuropein and ligstroside aglycons, hydroxytyrosol and tyrosol, were the phenolic compounds that statistically correlated with bacterial survival. These findings were confirmed by testing each individual phenolic compound, isolated by HPLC, against L. monocytogenes. In particular, the dialdehydic form of decarboxymethyl ligstroside aglycon showed a potent antimicrobial activity. These results indicate that not all oils classified as "olive oil" had similar bactericidal effects and that this bioactivity depended on their content of certain phenolic compounds.     

Biological activity of acetylated phenolic compounds

In recent years an effort has been made to isolate and identify biologically active compounds that are included in the Mediterranean diet. The existence of naturally occurring acetylated phenolics, as well as studies with synthetic ones, provide evidence that acetyl groups could be correlated with their biological activity. Platelet activating factor (PAF) is implicated in atherosclerosis, whereas its inhibitors seem to play a protective role against cardiovascular disease. The aim of this study was to examine the biological activity of resveratrol and tyrosol and their acetylated derivatives as inhibitors of PAF-induced washed rabbit platelet aggregation. Acetylation of resveratrol and tyrosol was performed, and separation was achieved by HPLC. Acetylated derivatives were identified by negative mass spectrometry. The data showed that tyrosol and its monoacetylated derivatives act as PAF inhibitors, whereas diacetylated derivatives induce platelet aggregation. Resveratrol and its mono- and triacetylated derivatives exert similar inhibitory activity, whereas the diacetylated ones are more potent inhibitors. In conclusion, acetylated phenolics exert the same or even higher antithrombotic activity compared to the biological activity of the initial one.     

Antioxidant activity of phenolic compounds isolated from Mesona procumbens Hemsl

The antioxidant activity of phenolic compounds isolated from Mesona procumbens Hemsl. (Hsian-tsao) was investigated. Hsian-tsao was extracted with various solvents, and the results showed that the fraction treated with acidic ethyl acetate (pH 2) possessed large amounts of phenolic compounds and a strong antioxidant activity on peroxidation of linoleic acid. The antioxidant activity (inhibition of peroxidation, IP%) of the acidic ethyl acetate of Hsian-tsao extract at 50 microg/mL (98.9%) was stronger than those of 50 microg/mL alpha-tocopherol (78%) and BHA at 10 microg/mL (90%). When fractionated with Amberlite XAD-7 gel chromatography, the acidic ethyl acetate fraction of Hsian-tsao extract was separated into four subfractions (A-D). Subfraction B, with high yield and strong antioxidant activity, was further isolated and purified and then identified as containing protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, and syringic acid by means of UV, EI-MS, and (1)H and (13)C NMR. The antioxidant capability of isolated compounds was also determined using the thiocyanate system and the erythrocyte ghost system. The results indicate that the phenolic acids could be important antioxidant components in Hsian-tsao, among which caffeic acid with the highest antioxidant activity and the greatest content is most important.     

Hydroxycinnamic acid amide derivatives, phenolic compounds and antioxidant activities of extracts of pollen samples from Southeast Brazil

Seven bee pollen samples (C1-C7) with different palynological sources were harvested from Pindamonhangaba municipality (Southeast Brazil). Methanol extracts of untreated samples (control), samples frozen at -18 °C and samples frozen and then dried were analyzed by HPLC/PAD/ESI/MS/MS. Flavonoid diglycosides of quercetin, kaempferol, isorhamnetin and patuletin were detected, together with hydroxycinnamic acid amide derivatives, such as N',N',N'-tris-p-feruloylspermidine and N',N',N'-tris-p-coumaroylspermidine. Distinct phenolic profiles characterized the analyzed samples, but no differences were noted as resulting from different treatments. Total phenolic contents determined with the Folin-Ciocalteau reagent ranged from 1.7 to 2.2%. Antioxidant activities above 75%, based on the DPPH method, were observed for all extracts, not correlated with total phenolic contents. Among samples from the same origin, those frozen were more active than samples untreated (control), and the samples frozen and then dried were the most active.