Free Phenolic Fraction Research Articles

Improving free, conjugated, and bound phenolic fractions in fermented oats (Avena sativa L.) with Monascus anka and their antioxidant activity

This work aims to investigate the effects of fermentation with Monascus anka on the phenolic components and antioxidant activities of oats. Results revealed that the fermentation process significantly increased total phenolic content, especially free phenolic content. Moreover, the dominate phenolic compositions of free, conjugated and bound phenolic fractions from oats varied with fermentation. Both catechin in free phenolic fraction and ferulic acid in bound phenolic fraction were enhanced more than 100-fold, while the amount of newly generated rutin was up to 355.07mg/kg in the conjugated fraction. All three phenolic fractions from fermented oats, especially the conjugated fraction, demonstrated greater DPPH and ABTS+ radical scavenging abilities than that of unfermented oats. It was revealed that most of the phenolic compounds had a strong positive correlation with antioxidant activities. Consequently, fermentation may be a potential approach to improve oats’ phenolic content and antioxidant capacity for functional foods in health promotion.

Distribution of free, esterified, and insoluble bound forms of phenolics in tea seeds and their antioxidant activity.

In this study, phenolic compounds in their phenolic extract (PE), free phenolic (FP), esterified phenolic (EFP), and insoluble bound phenolic (ISBP) forms were extracted from tea seeds and quantified using HPLC to obtain information on the phenolics that are present in tea seeds along with their antioxidant activities. The total phenolic content of the ISBP fraction was higher than that of the FP and EFP fractions. The phenolic acids in tea seeds exist either in esterified or glycosided forms. Moreover, hydroxycinnamic acid derivatives have been identified as important phenolic acid components in tea seeds. The ISBP fraction was an effective antioxidant based on the results obtained from the in vitro assays performed, which include the DPPH and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)-derived nitrogen-centered radical scavenging activities, Fe3+-2,4,6-tripyridyl-s-triazine reducing ability, as well as Cu2+ and Fe2+ ion chelating effects.

Optimized methodology for the extraction of free and bound phenolic acids from Chilean Cristalino corn (Zea mays L.) accession

ABSTRACTThe aim of this study was to optimize the extraction of free and bound phenolic acids from Chilean Cristalino corn by response surface methodology based on the total phenolic contents (TPCs) and the 2,2-diphenyl-1-picrylhydrazyl scavenging-linked antioxidant capacity (AC) as response variables. Central Composite 22 + axial points experimental designs were applied. The best extraction conditions for the free and bound phenolic fraction were acetone 69% in water for 63 min and a hydrolysis with 3 M NaOH for 90 min, respectively. Under these conditions, TPCs in free and bound forms were 59.9 ± 0.7 and 172.9 ± 1.1 mg gallic acid equivalents/100 g, respectively. Further, AC found in free and bound fractions was 186 ± 3 and 694.5 ± 3.3 µmol Trolox equivalents/100 g, respectively. The experimental and predicted values of TPC and AC were similar in case of free phenolic fraction indicating that the model was adequate and reproducible. Major phenolic acids were found in the bound fraction and were ferulic and p-coumaric acids.

Determination of contents and antioxidant activity of free and bound phenolics compounds and in vitro digestibility of commercial black and red rice (Oryza sativa L.) varieties

Black and red rices (Oryza sativa L.) were analysed for total flavonoids and phenolics and the HPLC profile including both free and bound phenolic fractions. Moreover, antioxidant activity and in vitro digestibility was determined. Content of flavonoids and polyphenols as well as antioxidant activity was higher in free phenolic fractions. Bound flavonoids in black rices were not significant contributors to antioxidant activity. The main free phenolics in black rices were ferulic, protocatechuic and trans-p-coumaric acids, while the major free phenolics in red rices were catechin, protocatechuic and caffeic acids. The main bound phenolics in black rices were ferulic and vanillic acids and quercetin, in red rice types, they were ferulic, syringic, trans-p-coumaric acids and quercetin. Newly, the presence of m-coumaric acid in red rices was detected. Steam cooked rices showed very high levels of organic matter digestibility, whereas red rices were significantly more digestible than black rices (p<0.05).

Determination of free and bound phenolics using HPLC-DAD, antioxidant activity and in vitro digestibility of Eragrostis tef

White and brown Eragrostis tef were assessed for total flavonoid and phenolic content, HPLC profile of the most common phenolics and antioxidant activity including both free and bound phenolics. Antioxidant activity was evaluated in correlation with free and bound phenolics and in vitro digestibility was determined. Content of flavonoids (0.52–1.02mg RE/g) and phenolics (0.90–1.42mg GAE/g) as well as antioxidant activity (1.70–4.37μmol TEAC/g using ABTS method) was higher in free phenolic fraction. Correlation showed that bound flavonoids were not significant contributors to antioxidant activity (R2=0.4513 and 0.4893, respectively). The main free phenolics in brown teff were trans-p-coumaric, protocatechuic, ferulic and gallic acids, while the major free phenolics in white teff were rutin, protocatechuic and ferulic acids. The main bound phenolics in brown teff were ferulic and gallic acids, quercetin and catechin, in white teff ferulic acid, rutin, catechin and quercetin. Cooked teff showed very high level of in vitro organic matter digestibility (80.5–85.1%), whereas brown teff was significantly more digestible than white teff (P<0.05).

Gamma-irradiation induced changes in microbiological status, phenolic profile and antioxidant activity of peanut skin

The effects of gamma-irradiation on the microbial growth, phenolic composition, and antioxidant properties of peanut skin were evaluated. Gamma-irradiation at 5.0 kGy decreased the microbiological count of the product. Total phenolic and proanthocyanidin contents, ABTS radical cation, DPPH radical, H2O2, and hydroxyl radical scavenging capacities as well as the reducing power of the sample were increased upon gamma-irradiation in both the free and insoluble-bound phenolic fractions. However, a decrease in the esterified phenolics was noticed. The bioactivity of the free phenolics against in vitro human LDL-cholesterol oxidation and copper induced DNA strand breakage was improved upon gamma-irradiation. Phenolic acids, flavonoids, and proanthocyanidins were positively or tentatively identified by HPLC-DAD-ESI-MSn and their distribution was in the decreasing order of free > esterified > insoluble-bound forms. Procyanidin dimer A was increased in all phenolic fractions, whereas procyanidin dimer B decreased. Gamma-irradiation induced changes may be explained by molecular conversion, depolymerization, and cross-linking.

Total phenolics, total anthocyanins and antioxidant capacity of native and elite blue maize hybrids (Zea mays L.)

Free and bound phenolics, antioxidant capacity and anthocyanins content of five elite blue maize hybrids and two native blue varieties grown in Mexico highlands were evaluated. Phenolic content of free and bound fractions was found from 1037 to 1488 and from 9064 to 11,987 mg gallic acid/kg, respectively. The free phenolic fraction of hybrid maize showed 3.7-fold higher hydrophilic antioxidant capacity than landrace counterparts. The highest anthocyanin content was found in hybrid 503 × 67 (1052 mg Cy3Glu/kg), which represented 73.1% of the free phenolics. Results indicated that elite blue maize hybrids could be an important source of antioxidant compounds with potential for either food or nutraceutical industries.

The Use of TLC-DPPH• Test with Image Processing to Study Direct Antioxidant Activity of Phenolic Acid Fractions of Selected Lamiaceae Family Species

TLC coupled with 2,2-diphenyl-1-picrylhydrazyl staining was used to analyze phenolic acid fractions of selected Salvia and Thymus species. Documented videoscans were processed by means of an image processing program. This is the first time that free phenolic acids fractions, as well as fractions containing phenolic acids derived from basic and acidic hydrolysis, have been analyzed and compared for selected sage and thyme species. The analyzed samples along with caffeic acid (CA; standard) were chromatographed on silica gel plates with toluene-ethyl acetate-formic acid (60 + 40 + 1, v/v/v) mobile phase. The extracts were investigated with respect to the activity of CA. It was found that CA was most abundant in the fractions derived from basic hydrolysis. This compound was not detected in any of the fractions obtained after acidic hydrolysis. S. officinalis and S. triloba have similar free radical scavenging activity fingerprints obtained for all the analyzed fractions.

Phenolic profile and antioxidant activity in selected seeds and sprouts

The aim of this study was to investigate the effect of germination on the phenolic acids and flavonoids profile, as well as antioxidant activity (AA), in selected edible seeds of mung beans, radish, broccoli and sunflower. Germination increased the total phenolic (TP) and flavonoid (TF) levels, as well as the AA of the seeds, and influenced the profile of free and bound phenolic compounds. Among the samples, mung bean was characterised by lowest levels of TP and TF, as well as AA, evaluated using ABTS, DPPH and FRAP assays. Sunflower and radish sprouts were the most rich in phenolic compounds. Insignificant amounts of free phenolic acids were found in the free phenolic acid fraction; alkaline hydrolysis of the seeds and sprouts extracts provided the majority of the phenolic acids. The amounts of free and bound flavonoids were inconsiderable both for seeds and sprouts.

ANALYSIS OF IN VITRO AND IN VIVO ANTIOXIDANT PROPERTIES OF HYDROPHILIC FRACTIONS FROM THE SEAWEED HALIMEDA MONILE L.

ABSTRACT In this work, in vitro and in vivo antioxidant properties of the marine algae Halimeda monile were assessed and the levels of some of its compounds likely to be responsible for such properties were determined. The estimated contents of total polyphenols, chlorophylls a and b and carotenoids were 179.5, 356.3, 452.8 and 42.2 µg/g dry weight seaweed, respectively. The presence of terpenoids and flavonoids was also observed. The antioxidant activity of two polar fractions from H. monile (lyophilized aqueous extract and free phenolic acid fraction) was evaluated using three antioxidant assays: ferric reducing antioxidant power, 1,1-diphenyl-2-picrylhydrazyl and lipid peroxidation. Treatment of CCl4-induced liver damage in rats with extracts resulted in lower serum thiobarbituric acid-reactive substances levels and higher hepatic glutathione concentrations compared to those observed in the CCl4-treated group. Also, a significant increase in catalase activity was detected after treatment with the extracts. These results suggest that the seaweed H. monile could be a potential source for natural antioxidants. PRACTICAL APPLICATIONS Seaweeds have a broad chemical composition, consisting of bioactive molecules as chlorophyll, carotenoids, mycosporine-like amino acids, terpenoids, carbohydrates, vitamins and phenolic compounds. Different seaweed extracts have received increased attention, due to their pharmacological effects, particularly in vivo hypolipidemic, antioxidant, immunological and antitumoral activities. The phenolic compounds are powerful antioxidant molecules, and fractions rich in these compounds may be use as antioxidant complement in health states where oxidative state is damage. Results of this research with Halimeda monile L. fractions showed in experiments in vitro and in vivo the presence of different phenolic compounds and that the antioxidant activity is related to them. Therefore, the H. monile L. seaweed fractions have the potential to be developed into new health foods.

Determination of antioxidant activity in free and hydrolyzed fractions of millet grains and characterization of their phenolic profiles by HPLC-DAD-ESI-MS n

Over 50 phenolic compounds belonging to several classes, namely, phenolic acids and their derivatives, dehydrodiferulates and dehydrotriferulates, flavan-3-ol monomers and dimers, flavonols, flavones and flavanonols in four phenolics fractions of several whole millet grains (kodo, finger (Ravi), finger (local), foxtail, proso, little and pearl millets) were positively or tentatively identified using high performance liquid chromatography (HPLC) and HPLC-tandem mass spectrometry (MS n). Total phenolic content (TPC) was determined colourimetrically using Folin–Ciocalteu reagent. Antioxidant and antiradical activities of phenolic fractions were estimated using oxygen radical absorbance capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, and singlet oxygen scavenging activity. In addition, antioxidant activities of phenolic fractions were determined in a β-carotene linoleate emulsion system. Insoluble bound fraction of kodo millet showed the highest phenolic content as well as antioxidant activity in the in vitro test systems employed. In general, hydroxycinnamic acids and their derivatives were the main contributors (87–98%) to the TPC of insoluble bound phenolic fraction of millet varieties examined. Flavonoids were predominantly present in the free phenolic fractions of two finger millet varieties and included catechin, epicatechin, gallocatechin, epigallocatechin, and procyanidin dimers B1 and B2 among others. The degree of esterification or etherification of phenolics with sugar residues in the soluble fraction changed with the variety. Thus millet grains may serve as a viable functional food ingredient and a source of natural antioxidants.

Effect of steam treatment on soluble phenolic content and antioxidant activity of the Chaga mushroom (Inonotus obliquus)

Abstract The effect of steam treatment on free phenolic acids in Chaga mushrooms (Inonotus obliquus) was investigated. Untreated and steam-treated (120 °C, 3 h) samples of I. obliquus were extracted with organic solvents and free phenolic acid-containing fractions were isolated. Free phenolic acids were determined by LC/PDA (liquid chromatography/photodiode array), ESI LC/MS (electrospray ionisation liquid chromatography/mass spectrometry), and GC/MS (gas chromatography/mass spectrometry). After the steam treatment, the soluble phenolic content determined by modified Folin–Ciocalteu method was increased and antioxidant activity was enhanced, as confirmed by a DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity assay. The amounts of vanillic acid, protocatechuic acid, syringic acid, and 2,5-dihydroxyterephthalic acid were increased significantly as the result of the steam treatment, suggesting that the liberation of low molecular weight free phenolics was enhanced by the steaming process. Consequently, the radical scavenging activity was also significantly enhanced by free phenolics produced using this method.

Fermentation Changes the Nutritive Value, Polyphenol Distribution, and Antioxidant Properties of Parkia biglobosa Seeds (African Locust Beans)

This present study was carried out to investigate the effect of natural fermentation on the nutritive value (proximate composition), polyphenolic distribution, and antioxidant properties of African locust beans (Parkia biglobosai). African locust bean (ALB) seeds were boiled for 12 h, dehulled and subjected to natural solid substrate fermentation without any inoculation for 4 days. The proximate composition of the fermented and unfermented locust bean seeds was subsequently determined. Thereafter, the polyphenol distribution, reducing power, DPPH free-radical scavenging antioxidant activity, and inhibition of lipid peroxidation were determined for soluble free and bound polyphenol extracts. The results of the study revealed that fermentation caused a significant increase (P < 0.05) in the ALB protein content with 18.3% in unfermented and 36% in fermented. The fat content in unfermented was 13.2% versus 26.8% in fermented, while there was no significant changes (P > 0.05) in ash, crude fiber, or moisture content. However, there was a significant decrease (P < 0.05) in the carbohydrate content. The total phenolic content, reducing ability and free-radical scavenging ability were high in both the fermented and unfermented ALB. Fermentation caused a significant increase (P < 0.05) in the free phenolic content of the ALB and a significant decrease (P < 0.05) in the bound phenolic content of ALB. The free-phenolic fraction from both fermented and unfermented ALB had high reducing power, free radical scavenging ability, and inhibition of lipid peroxidation using cow brain tissues. Free phenolic extract from the fermented ALB had a significantly higher (P < 0.05) antioxidant activity than that of unfermented ALB. Results suggest that fermentation will increase the nutritive values, free phenolic and antioxidant activity of the African locust bean, making it a potential functional food in addition to its traditional role of dietary protein source.

Availability of blueberry phenolics for microbial metabolism in the colon and the potential inflammatory implications

Blueberries are a rich source of phenylpropanoid-derived phytochemicals, widely studied for their potential health benefits. Of particular interest for colonic health are the lower molecular weight phenolic acids and their derivatives, as these are the predominant phenolic compounds detected in the colon. Blueberries contained a wide variety of phenolic acids, the majority of which (3371.14 +/- 422.30 mg/kg compared to 205.06 +/- 45.34 mg/kg for the free phenolic acids) were attached to other plant cell-wall components and therefore, likely to become available in the colon. Cytokine-induced stimulation of the inflammatory pathways in colon cells was four-fold up-regulated in the presence of the free phenolic acid fraction. Incubation of the bound phenolic acids with human faecal slurries resulted in qualitative and quantitative differences in the phenolic compounds recovered. The metabolites obtained by incubation with faecal slurries from one volunteer significantly decreased (1.67 +/- 0.69 ng/cm(3)) prostanoid production, whereas an increase (10.78 +/- 5.54 ng/cm(3)) was obtained with faecal slurries from another volunteer. These results suggest that any potential protective effect of blueberry phenolics as anti-inflammatory agents in the colon is a likely result of microbial metabolism. Studies addressing a wide-range of well-characterised human volunteers will be required before such health claims can be fully established.

Influence of Sample Preparation on Assay of Phenolic Acids from Eggplant

Sample preparation is often overlooked and is frequently considered as "a means to an end". This systematic study with a phenolic-enriched substrate, eggplant (Solanum melongena L.), was undertaken to evaluate the substantial variations in the extraction techniques, solvents, and parameters as described in the published literature. Direct comparison of over 10 extraction procedures or conditions was performed to show the importance and influence of sample preparation on the assay of phenolic compounds. Chlorogenic acid (CA) was the most abundant phenolic acid accounting for >75% of the total phenolic acids content extracted from the eggplant sample. Optimum extraction of CA and total phenolics (TP) from Black Bell cultivar of eggplant were obtained when extractions were performed with a mixture of MeOH/H2O at a ratio of 80:20% v/v using a pressurized liquid extractor (PLE) at 100 degrees C. The amount of CA and TP extracted from eggplant by the previously reported procedures using a wrist shaker, rotary shaker, stirring, sonication, or reflux with different extraction solvents (acetone or varying composition of MeOH/H2O solvent mixtures) varied significantly between 5 and 95% as compared to PLE. The predominant phenolic acids in the free phenolic acid fraction of Black Beauty cultivar of eggplant were CA isomers. However, caffeic acid isomers were the major phenolic acids extracted from the base-hydrolyzed fraction. The total amount of caffeic acid extracted from the Italian Neon cultivar was more that twice that of four other eggplant cultivars (Orient Express, Calliope Zebra Stripe, Orient Charm Neon, and Black Beauty).

Use of two-dimensional TLC to identify phenolic acids in the foliage and fruit ofPeucedanum tauricumBieb

Two-dimensional planar chromatography (2D TLC) on cellulose layers, solid phase extraction (SPE), and reversed-phase high-performance liquid chromatography (HPLC) have been used for purification, separation, and identification of the phenolic acids in the foliage and fruits of Peucedanum tauricum Bieb. ( Umbelliferae = Apiaceae ). Methanolic extracts of the foliage and fruit were purified and the free phenolic acids fractions were isolated by means of the classical method of Ibrahim and Towers . Hydrolysis of the esters and glycosides was performed by the method of Schmidtlein and Herrmann . Isolated fractions containing phenolic acids were investigated by comparison with standards, by means of analytical 2D TLC on cellulose layers, by use of derivatization reagents (gaseous NH 3 , 3% FeCl 3 and diazotized sulfanilic acid in 20% sodium carbonate solution), and by RP HPLC with isocratic elution (mobile phase methanol-water, 20:80 ( v / v ) containing 1% ( v / v ) acetic acid) and UV spectroscopy (by means ...

TLC and HPLC analysis of the phenolic acids inSilphium perfoliatumL. Leaves, inflorescences and rhizomes

TLC and HPLC have been used for preliminary evaluation of the phenolic acids occurring in the leaves, inflorescences, and rhizomes of Silphium perfoliatum L. Free phenolic acids and those released after acidic and basic hydrolysis were subjected to chromatographic analysis. Qualitative TLC analysis was performed by one- and two-dimensional ascending development on plates coated with cellulose, polyamide 11 F 254 , and silica-gel 60 F 254 . Reversed-phase HPLC was performed with photodiode-array detection.Seven phenolic acids were present, in the free and bonded forms, in the raw material studied. Caffeic and protocatechuic acids occurred in all the fractions analyzed. p -Coumaric and p -hydroxybenzoic acids were identified in all the free phenolic acid fractions. Ferulic acid was found in inflorescences and rhizomes and vanillic acid in leaves and inflorescences. After acidic hydrolysis chlorogenic acid was identified in leaves and p -hydroxybenzoic and vanillic acids in inflorescences. After basic hydrol...

Phenolic acids of borage (Borago officinalis L.) and evening primrose (Oenothera biennis L.)

AbstractThe composition of phenolic acids, both free and liberated from esters and glycosides, was determined in evening primrose and borage seeds by GC and MS. The free phenolic acid fraction was predominant in these seeds. Protocatechuic acid was the principal phenolic acid of the free and esterified phenolic acids in evening primrose seeds. Ferulic acid represented a high proportion of the free phenolic acids, but hydroxycaffeic acid was the major constituent of phenolic acids liberated from esters of borage seeds.

Germination inhibitors in bracts surrounding the grain of Triticum tauschii

Pre-harvest sprouting of bread wheat is a cause of considerable economic losses for the Australian wheat industry. In this study, we have used Triticum tauschii (Coss.) Schmahl., the donor of the D-genome to bread wheat, and identified water-soluble germination inhibitors in its bracts. Germination of non-dormant T. tauschii grains was significantly delayed by imbibition in undiluted leachate (crude extract) from the bracts, whereas any dilution of the crude extract (1/10, 1/100 or 1/1000) resulted in no inhibition. Removal of proteins larger than 10 kDa from the crude extract resulted in increased germination inhibition compared with the crude extract. When purified, free phenolic compounds present in the crude extract were found to inhibit germination, but to a lesser extent than the crude extract, possibly due to losses during purification. HPLC of the free phenolic fraction indicated the presence of more than 30 compounds. Peak fractions were collected and tested for inhibitory properties. Two fractions significantly inhibited grain germination for 3 d, with one fraction, determined to contain vanillic acid, continuing to inhibit germination after 5 d. Exogenously applied vanillic acid at a concentration of 0.2 mg mL-1 was shown to significantly inhibit germination compared with water-imbibed grains. The germination inhibitor mechanism detected in the bracts surrounding the grain of T. tauschii in this study has the potential to provide protection against pre-harvest sprouting in bread wheat.

Alternations in phenolic acids content in developing rye grains in normal environment and during enforced dehydration

A series of high pressure liquid chroamtography analyses revealed the presence of five phenolic acids in rye caryopses (vanillic, caffeic, p-coumaric, ferulic and sinapic), three of which (p-coumaric, ferulic and sinapic) were found in the free phenolic fraction. Ferulic acid was predominant, both among free acids and total phenolic acids (i.e. free, liberated from soluble esters and glycosides). The highest content of the free phenolic acids in rye caryopses was observed at the beginning of development, when on 22 DAF it was estimated at 11.55 µg·g−1 DW. During dehydratation the total level of free phenolic acids in rye caryopses decreased in all investigated samples. Although total phenolic acids contents in all samples of unripe rye caryopses always decreased after dehydration, in rye sample collected in full ripeness (57 DAF), the amount of these compounds increased after the enforced dehydration. It should be added that in ester-bound-soluble phenolic acids fraction (the largest part in the total phenolic acids fraction), irrespective of the total amount decrease, much increase of sinapic acid content in this fraction was observed after dehydratation treatment in all investigated samples of caryopses of various ripeness. During the development and ripening of rye caryopses, a gradual increase in the precocious germination ability of the grain was observed. The enforced dehydration stimulated the process of precocious germination of developing and ripening rye caryopses. A possible role of phenolics in preventing precocious germination and acclimation to dehydration of developing and ripening rye grains is discussed.