The occurrence and characterisation of phenolic compounds in Camelina sativa seed, cake and oil

In this study, the antioxidant activities of Camelina sativa methanolic extracts were evaluated by different chemical assays: reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH·) assay, the β-carotene bleaching method and the metal chelating activity assay. An LC-MS profiling method was used for a comprehensive study of the phenolic compounds and their representation in camelina seeds, cake and oil. For this purpose, 4-vinyl derivatives of hydroxycinnamic acids were synthesized by thermal decarboxylation of the corresponding phenolic acids and sinapine was isolated from kale (Brassica oleracea) applying a new method and confirmed by NMR. The results revealed that besides the total phenolic content and antioxidant activity, seeds and cake also possess a similar phenolic profile. In addition to sinapine and 4-vinyl derivatives, other antioxidants were successfully identified: ellagic acid, protocatechuic acid, p-hydroxybenzoic acid, sinapic acid, salicylic acid, catechin, rutin, quercetin and quercetin glucoside. Since after oil pressing most of the phenolic compounds remain in the seed residues, only a few compounds were identified in the oil. Camelina cake was found to have the best reducing power and radical scavenging activity, whereas camelina oil, with a relatively low phenolic content, exhibited the highest iron-chelating capacity and the best inhibitory action against β-carotene discolouration in an emulsified system.     

Phenolic profiles and antioxidant activities of commercial beers

The phenolic profiles and corresponding antioxidant activities of 34 commercial beers in Chinese markets were evaluated. Results found remarkable variations in total and individual phenolic contents as well as antioxidant activity across beer brands. Gallic and ferulic acids were the dominant phenolic compounds identified in the tested beer samples and both of them accounted for >50% of the total phenolic compounds. Results from Pearson correlation analysis suggested that five antioxidant activity assays positively correlated well (p < 0.01) with each other and showed significant positive correlations (p < 0.05) with (+)-catechin, protocatechuic, and caffeic acids contents. Stepwise linear regression further demonstrated that different phenolic components responsible for beer antioxidant activity were dependent on the method used, and that ferulic acid, syringic acid, (+)-catechin, caffeic acid, protocatechuic acid and (−)-epicatechin together made 55.0–88.1% of contribution to the antioxidant activity of beer.     

The effects of solvents on the phenolic contents and antioxidant activity of Stypocaulon scoparium algae extracts

Water, water/methanol (1/1), methanol and ethanol crude extracts from a brown alga Stypocaulon scoparium were examined for total phenolic contents (TPC) using Folin–Ciocalteu method. DPPH scavenging assay was performed to measure the radical scavenging activities (RSA) of the extracts. Results showed a significant association between the antioxidant potency and the TPC. The aqueous extract showed both, the highest antioxidant activity and highest phenolic contents. The identification and quantification of phenolic antioxidants were carried out with a rapid and simple method of reverse phase high performance liquid chromatography (RP-HPLC). This method was developed for the simultaneous analysis of 14 polyphenols, namely gallic acid, catechin, epicatechin, rutin, p-coumaric acid, myricetin, quercetin and protocatechuic, vanillic, caffeic, ferulic, chlorogenic, syringic and gentisic acids. The chromatographic separation of 14 polyphenols was achieved in less than 40 min by RP-HPLC (Varian, Pursuit XRs C18 column, 5 μm, 250 mm × 4.6 mm) using linear gradient elution of methanol and water (0.1% formic acid) with a flow rate of 1 ml/min. Gallic acid was by far the predominant polyphenol.     

Antioxidant properties of commercial wild rice and analysis of soluble and insoluble phenolic acids

To investigate the antioxidant properties of commercial wild rice, identify and quantify soluble and insoluble phenolic acids in wild rice whole grain, the alkaline hydrolysates from crude methanol extracts (soluble fraction) and residues (insoluble fraction) were separately analysed by high performance liquid chromatography (HPLC) coupled with photodiode array detection (PAD) and quadrupole-time of flight (Q-TOF) mass spectrometry (LC–MS). The antioxidant activity of wild rice methanol extract was found to be up to 10 times greater than that of white rice (control sample) according to their 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC). Ferulic acid was found as the most abundant phenolic acid (up to 355 mg/kg) followed by sinapic acid in wild rice. They both occurred mainly in the insoluble form. Other monomeric phenolic acids present in wild rice consisted of p-coumaric, vanillic, syringic, and p-hydroxybenzoic acids, along with two phenolic acid aldehydes (p-OH-benzaldehyde and vanillin). They were present in both soluble and insoluble forms. Phenolic acid dehydrodimers are cell wall bound and only appeared in the insoluble fractions featured by diferulic acids (DiFA) and disinapic acids (DiSA). The chemical structures of DiFA included 8-8′, 5-5′, 8-O-4′, and 8-5′ (benzofuran form) coupled dimers, with 8-O-4′ as the predominant form (up to 34 mg/kg). DiSA only appeared as 8-8′-coupled products with the linear isomers in the most quantities (up to 19 mg/kg). The DPPH free radical scavenging activities of soluble and insoluble fractions suggest that the antioxidant activity of wild rice is partially attributed to its phenolic acid profile.     

Retention of antioxidant activity in gamma irradiated argentinian sage and oregano

The effect of 30 kGy of gamma radiation on the antioxidant activity of methanolic and aqueous extracts prepared from dry gamma irradiated sage and oregano were analysed. The antioxidant activity was characterised by DPPH radical test and by reducing power assay within an extract concentration range of 0–40 mg/ml of methanol or water. In addition, the total phenolic content in the extracts was determined. From the EC₅₀ estimated values, it was established that, by both methods, oregano extracts showed a higher antioxidant activity than sage extracts. Oregano extracts also showed a phenolic content significantly higher than sage extracts. A good correlation between the phenolic content and the antioxidant activity was also observed. The 30 kGy dose applied to dry sage and oregano for sanitization did not significantly affect the capacity to inhibit the DPPH radical or the reducing power, nor did it affect the total phenolic content of the methanolic and aqueous extract.     

Radiation-induced enhancement of antioxidant activity in extracts of rosemary (Rosmarinus officinalis L.)

Dry rosemary leaf powder was subjected to 30 kGy of gamma ray irradiation, followed by solvent extraction with methanol, ethanol or water. The antioxidant activity of the extracts was assessed using the DPPH radical-scavenging method and the reducing power test. EC₅₀ values, using the radical-scavenging method, indicate a 22% increase in the antioxidant activity of ethanol and water extracts as a result of irradiation treatment. EC₅₀ values in the reducing power test show an increase of 45% and 28% for the ethanol and water extracts, respectively. The antioxidant activity of methanol extracts of irradiated rosemary remained the same as in the controls in both types of test. A high correlation was found between the EC₅₀ values obtained in the DPPH radical test and those from the reducing power test. Total phenolic content (Folin–Denis test) increased by 35% in the water extracts as a result of irradiation but remained the same in the methanol and ethanol extracts. The methanol extract showed the highest antioxidant activity and the highest amount of total phenolic compounds. Radiation reduced the good correlation between antioxidant activity and total phenolic content.     

Optimization of Phenolic Content,Antioxidant, and Inhibitory Activities of α-Glucosidase and Angiotensin Converting (AC) Enzymes from Zingiber officinale Z.

The optimum extraction conditions of phenolic compounds from ginger were evaluated with respect to antioxidant activity and angiotensin converting enzyme and α-glucosidase inhibitory activities. Free phenolics were extracted under conditions that varied according to extraction time, temperature, and solvent type (water, acetone, and methanol). Acid and base hydrolysis reactions were used to obtain bound phenolic compounds from ginger. The results showed that the type of solvent used and the temperature and time of extraction needed for maximal total phenolic content, antioxidant activity, and angiotensin converting enzyme inhibitory activity differed greatly from solvent conditions and showed the greatest α-glucosidase inhibitory activity. The predominant free phenolics in the methanol extracts included diosmin, thymol, and carvacrol, which varied greatly according to solvent extraction conditions (i.e., time and temperature). Diosmin was the predominant bound phenolic compound of the methanol extracts. The present study findings indicate that differing solvent extraction protocols involving extraction time and temperature for ginger need to be explored to generate specific optimal bioactivities of the extracts, which are related to the pattern of predominant phenolics in those extracts.     

Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes.     

Antioxidant phenolic compounds loss during the fermentation of Chétoui olives

Evolution of phenolic compounds was studied during spontaneous and controlled fermentations of “Chétoui” cultivar olives at three degree of ripeness. Both spontaneous and controlled fermentations led to an important loss of total phenolic compounds with a reduction rate of 32–58%. Consequently, the antioxidant activity decreased by 50–72%. After fermentations, hydroxytyrosol and caffeic acid concentrations increased, whilst protocatechuic acid, ferulic acid and oleuropein concentrations decreased. The hydroxytyrosol concentration in black olives increased from 165 mg/100 g dry weight to 312 and 380 mg/100 g dry weight, respectively, after spontaneous and controlled fermentation. The oleuropein concentration in green olives decreased from 266 mg/100 g dry weight to 30.7 and 16.1 mg/100 g dry weight, respectively, after spontaneous and controlled fermentation. During olive fermentation, phenolic loss is essentially due to the diffusion of these compounds into the brine; the main phenolic compound identified and quantified in the different brines was hydroxytyrosol. To preserve antioxidant quality of table olives it is necessary to use a controlled process to minimise phenolic compound loss.     

Antioxidant properties of various solvent extracts of potato peel,sugar beet pulp and sesame cake

BACKGROUND: Growing interest in the replacement of synthetic food antioxidants by natural ones has fostered research on vegetable sources and screening of raw materials to identify new antioxidants. The food‐processing industry generates substantial quantities of phenolic‐rich by‐products that could be valuable natural sources of antioxidants. In this study the antioxidant properties and total phenolic, flavonoid and flavonol contents of three industrial by‐products, sugar beet pulp, sesame cake and potato peel, extracted with various solvents were examined. Since different antioxidant compounds have different mechanisms of action, several methods were used to assess the antioxidant efficacy of extracts. RESULTS: Among the six solvents tested, methanol gave the highest extract yield of potato peel and sugar beet pulp, while diethyl ether gave the highest extract yield of sesame cake. Methanol exhibited the highest extraction ability for phenolic compounds, with total phenolics amounting to 2.91, 1.79 and 0.81 mg gallic acid equivalent g^?1 dry weight in potato peel, sugar beet pulp and sesame cake extracts respectively, and also showed the strongest antioxidant capacity in the three assays used. All three methods proved that potato peel extract had the highest antioxidant activity owing to its high content of phenolic compounds and flavonoids. CONCLUSION: On the basis of the results obtained, potato peel, sugar beet pulp and sesame cake extracts could serve as natural antioxidants owing to their significant antioxidant activity. Therefore they could be used as preservative ingredients in the food and/or pharmaceutical industries. Copyright © 2009 Society of Chemical Industry     

超声辅助提取瑭溪蜜柚皮中酚酸的研究

利用20kHz的超声波辅助提取琯溪蜜柚皮中的酚酸,主要研究了超声参数(超声时间、温度、超声功率)对琯溪蜜柚皮中的7种酚酸(咖啡酸、对香豆酸、阿魏酸、芥子酸、原儿茶酸、对羟基苯甲酸、香草酸)和黄酮糖苷(柚皮苷)的影响。结果表明:柚皮苷和酚酸的含量都随着超声时间和温度的增加而增加。超声功率对柚皮苷含量的影响较小,但对7种酚酸有不同程度的影响。确定了超声提取琯溪蜜柚皮中柚皮苷和酚酸的最佳提取条件:柚皮苷,超声30 min、超声温度40℃、超声功率8 W;酚酸,超声30 min、超声温度30℃、超声功率30 W。     

Study of the inhibitory activity of phenolic compounds found in olive products and their degradation by Lactobacillus plantarum strains

Lactobacillus plantarum is the main species responsible for the spontaneous fermentation of Spanish-style green olives. Olives and virgin oil provide a rich source of phenolic compounds. This study was designed to evaluate inhibitory growth activities of nine olive phenolic compounds against four L. plantarum strains isolated from different sources, and to explore the L. plantarum metabolic activities against these phenolic compounds. None of the nine compounds assayed (oleuropein, hydroxytyrosol, tyrosol, as well as vanillic, p-hydroxybenzoic, sinapic, syringic, protocatechuic and cinnamic acids) inhibited L. plantarum growth at the concentration found in olive products. Oleuropein and tyrosol concentrations higher than 100 mM were needed to inhibit L. plantarum growth. On the other hand, sinapic and syringic acid showed the highest inhibitory activity since concentrations ranging from 12.5 to 50 mM inhibited L. plantarum growth in all the strains analyzed. Among the nine compounds assayed, only oleuropein and protocatechuic acid were metabolized by L. plantarum strains grown in the presence of these compounds. Oleuropein was metabolized mainly to hydroxytyrosol, while protocatechuic acid was decarboxylated to catechol. Metabolism of oleuropein was carried out by inducible enzymes since a cell-free extract from a culture grown in the absence of oleuropein was unable to metabolize it. Independent of their isolation source, the four L. plantarum strains analysed showed similar behaviour in relation to the inhibitory activity of phenolic compounds, as well as their ability to metabolize these compounds.     

A comparative study on free and bound phenolic acid content and their antioxidant activity in bran of rice (Oryza sativa L.) cultivars of Eastern Himalayan range

In our study, seven most prevailing but unexplored indigenous rice cultivars of northeast India, situated in the Eastern Himalayan Range, were investigated for their phenolic acid profile, total phenolic content (TPC) and antioxidant capacities in free and bound phenolic extracts of their bran. HPLC studies showed the presence of ferulic, p‐coumaric, sinapic, caffeic, chlorogenic and vanillic acids, with ferulic and p‐coumaric acids being the dominant phenolic acids in the bound form. The lower EC₅₀ values of the bound extracts than the free extracts suggested the better radical scavenging activity of the bound extracts. Significant correlations were observed between TPC and phenolic acid content (HPLC‐DAD) of bound extracts, and between Trolox equivalents antioxidant capacity (TEAC) and phenolic acid content (HPLC‐DAD) of both free and bound extracts. The findings suggest that phenolic acids in the rice cultivars investigated were exclusively present in bound form and contribute significantly towards their antioxidant capacity.     

An investigation into green coffee press cake as a renewable source of bioactive compounds

The residual biomass of coffee, obtained after the oil extraction from coffee beans, called coffee beans residual press cake, has been attracted interest as a source of compounds with antioxidant capacity. This study investigated the effects of ethanolic and methanol-acetone extracts of green coffee beans (GCB) and its residual press cake (GCC) on the phenolic composition and antioxidant capacity. Antioxidant capacity was assayed through five different methods (total phenolic compounds, •DPPH, ABTS, FRAP and β-carotene bleaching assay), and the phenolic profile of the samples through High Performance Liquid Cromatography. GCB and GCC enclosed chlorogenic (55.16 and 64.96 mg g⁻¹, respectively) and caffeic (25.07 and 44.37 mg g⁻¹, respectively) acids as the major components, and the cake presented higher antioxidant capacity than the actual green bean. Antioxidant capacity was higher for GCC extracted with methanol and acetone. This study on the evaluation of the effects of the type of solvent on the bioactive compounds from GCB and GCC showed that this by-product can be a source of new value-added products, such as phenolic antioxidant adjuncts for food or pharmaceutic processing.     

Synergistic and suppressive effects of dietary phenolic acids and other phytochemicals from cereal extracts on nuclear factor kappa B activity

In this study the combinatorial action of the main phenolic acids (ferulic, caffeic, p-coumaric and sinapic acids) found in extracts of free (ME) and bound phenolic acids (HE) from oat, barley and wheat flour on the modulation of NF-κB activity was investigated. The results show that combination of phenolic acids in low concentrations (<0.1 μg/ml) has a significant synergistic, or enhanced effect, on NF-κB activity, while their combination in high concentrations (0.3–70 μg/ml) helps to suppress the strong effect obtained by individual solutions of ferulic and p-coumaric acids. The modulation of NF-κB activity observed by HE extracts is the effect of combinatorial action of the phenolic acids present therein, while the modulation of NF-κB activity observed with ME extracts is the result of combinatorial action of phenolic acids together with other phenolic compounds present in the extracts. These results increase the knowledge about the health promoting effect from cereal consumption and dietary phenolic acids.     

Phenolics, betacyanins and antioxidant activity in Opuntia joconostle fruits

Sour prickly pears (xoconostles) are fruits from Opuntia joconostle cactus, which are cultivated in the central Mexico area. Phenolic and pigment content in various parts of O. joconostle fruits were analyzed. The antioxidant activity of a methanolic extraction and different semi-purified fractions were also evaluated by the DPPH⁺ method. Xoconostle fruits were obtained from a commercial orchard in Mexico State. Fruits were analyzed as whole fruit and each fruit part including pericarp, mesocarp and endocarp. Samples were homogenized and kept at 4 °C until sample preparation. Total phenolic content and total flavonoid content varied among the different parts of the fruit. The highest amount of phenolic compounds and total flavonoids content were found in pericarp 2.07 mg gallic acid equivalents (GAE)/g fresh weight (FW) and 0.46 mg(+)-catechin equivalents (CE)/g FW respectively. Seven phenolics were identified as protocatechuic, 4-hydroxybenzoic, caffeic, vanillic and syringic acids, rutin, and quercetin. The color of the fruit parts was mainly due to the presence of betacyanins. The betacyanin concentration was higher in the endocarp (23.03 mg betanin equivalents/100 g fresh weight) than in the pericarp and mesocarp. Betacyanins were identified by HPLC-PDA-MS as betanin, isobetanin, betanidin, isobetanidin, and phyllocactin. Methanolic extracts and semi-purified fractions A (phenolics and flavonols) and B (betacyanins) of xoconostle showed high antioxidant activity mainly in the pericarp. These results suggest that xoconostle is a rich source of antioxidant compounds such as phenolic compounds and betacyanins.     

Development and validation of an HPLC-method for determination of free and bound phenolic acids in cereals after solid-phase extraction

Whole cereal grains are a good source of phenolic acids associated with reduced risk of chronic diseases. This paper reports the development and validation of a high-performance liquid chromatography–diode array detection (HPLC–DAD) method for the determination of phenolic acids in cereals in either free or bound form. Extraction of free phenolic acids and clean-up was performed by an optimised solid-phase extraction (SPE) protocol on Oasis HLB cartridges using aqueous methanol as eluant. The mean recovery of analytes ranged between 84% and 106%. Bound phenolic acids were extracted using alkaline hydrolysis with mean recoveries of 80–95%, except for gallic acid, caffeic acid and protocatechuic acid. Both free and bound phenolic extracts were separated on a Nucleosil 100 C₁₈ column, 5 μm (250 mm × 4.6 mm) thermostated at 30 °C, using a linear gradient elution system consisting of 1% (v/v) acetic acid in methanol. Method validation was performed by means of linearity, accuracy, intra-day and inter-day precision and sensitivity. Detection limits ranged between 0.13 and 0.18 μg/g. The method was applied to the analysis of free and bound phenolic acids contents in durum wheat, bread wheat, barley, oat, rice, rye, corn and triticale.     

High performance liquid chromatographic analysis of phenolic compounds and their antioxidant activities in rice varieties

The analytical method for the determination of phenolic compounds in rice varieties was developed. The method consisted of extraction of phenolic compounds from rice before analysis by high performance liquid chromatography (HPLC). Reversed phase HPLC equipped with photodiode array detection was used and the separation condition was optimized. Under the optimum condition, twelve phenolic compounds were separated within 24 min. Pressurized liquid extraction (PLE) was used to extract free phenolic compounds from rice with the optimum extraction condition of 70% methanol and extraction time of 15 min. While, bound phenolic compounds were extracted using alkaline hydrolysis for 15 min. Six varieties of Thai rice including pigment and non-pigment rice in their brown and polished forms were investigated. All of 12 phenolic compounds were detected as free phenolic compounds in all samples. Ferulic acid was the most abundant free phenolic compounds in all samples, while ferulic acid and p-coumaric acid were found as bound phenolic compounds in some samples. The content of phenolic compounds, total flavonoid and antioxidant activity detected in pigment rice and brown form were higher than non-pigment rice and polished form.     

A systematic survey of antioxidant activity of 30 Chinese medicinal plants using the ferric reducing antioxidant power assay

The antioxidant activities and total phenolic contents of 30 Chinese medicinal plants were evaluated using the ferric reducing antioxidant power assay and the Folin–Ciocalteu method, respectively. The Chinese medicinal plants were extracted by the traditional method, boiling in water and also in 80% methanol. A significant and linear correlation coefficient between the antioxidant activity and the total phenolic content was found in both aqueous (R² = 0.7917) and methanol (R² = 0.7584) extracts. Phenolic compounds are thus a major contributor of antioxidant activity. Comparing the extraction efficiency of the two methods, the boiling water method extracted phenolic compounds more efficiently, and antioxidant activity of the extract was higher. It was found that the Chinese medicinal plants Rhodiola sacra Fu, the stem of Polygonum multiflorum Thunb. and the root of P. multiflorum Thunb. possessed the highest antioxidant activities and thus could be potential rich sources of natural antioxidants.     

Phenolic compounds in Chinese purple yam and changes during vacuum frying

Phenolic compounds and their changes during vacuum frying were investigated for a Chinese purple yam. Three cyanidin derivatives and one peonidin derivative were tentatively identified by HPLC–DAD–ESIMS analysis; sinapic acid and ferulic acid were identified by HPLC–DAD analysis with authentic chemicals. There were 31.0 mg/100 g (dry weight, DW) of total anthocyanin (ACN) and 478 mg/100 g DW of total phenolic content (TPC) in the fresh yam. Sinapic acid and ferulic acid were 135 and 31.3 mg/100 g DW respectively. The blanching process caused about 60% of ACN, and 30–50% of phenolic acids and TPC to be lost, which showed that anthocyanins were most vulnerable during blanching. The retention rate of the phenolic compounds during vacuum frying was 60–69%, indicating it was a practical technology for purple yam processing, on account of its impact on the phenolic compounds stability.