Flavonoid pattern of sage (Salvia officinalis L.) unifloral honey

The aim of the present paper was to determine the flavonoids in monofloral sage (Salvia officinalis L.) honey which is characteristic and specific for the area of Croatian coast and islands. For that purpose 38 sage honey samples from two production seasons were analysed. After specific pollen content determination, and analyses of selected physicochemical parameters which confirmed that samples are in compliance with national and international regulations and can be regarded as unifloral sage honeys, flavonoid fraction was isolated and analysed using RP-HPLC/DAD method. The HPLC analysis showed that all examined sage honey samples contain quercetin (3,3′,4′,5,7-pentahydroxyflavone), luteolin (3′,4′,5,7-tetrahydroxyflavone), kaempferol (3,4′,5,7-tetrahydroxyflavone), apigenin (4′,5,7-trihydroxyflavone), chrysin (5,7-dihydroxyflavone) and galangin (3,5,7-trihydroxyflavone), as well as p-coumaric (trans-4-hydroxycinnamic acid) and caffeic acid (3,4-dihydroxycinnamic acid). Total amount of identified flavonoids varied from 109.4 μg/100 g of honey to 589.9 μg/100 g of honey, with the average of 288.5 μg/100 g of honey. All analysed honey samples showed common and specific flavonoid profile which could be the basis for differentiating sage from other monofloral honeys.     

Correlation analysis between phenolic levels of Brazilian propolis extracts and their antimicrobial and antioxidant activities

Propolis extracts are currently used for the treatment of oronasal infections and as antioxidant agents. Ethanolic commercial Brazilian propolis extracts were assayed for their ability to inhibit the growth of Staphylococcus aureus and also for their ability to scavenge DPPH radicals. These activities were correlated with their total phenolic and flavonoid levels. In one group of extracts there was a strong linear relationship between total phenol contents and the measured activities, while in the other group this relationship was weaker. It was also found that flavonoid levels had a greater influence on the antioxidant activity of these extracts than on their antimicrobial profiles.     

Screening of 70 medicinal plant extracts for antioxidant capacity and total phenols

The total phenolic content and related total antioxidant capacity of 70 medicinal plant infusions was analyzed. Infusions were prepared in common way in which teas are prepared for human consumption. The total phenolics were measured by Folin–Ciocalteau assay. The total antioxidant capacity was estimated by Ferric Reducing/Antioxidant Power (FRAP) assay. To make practical comparison of relative antioxidant potential of phenolics extracted from selected medicinal plants, the phenol antioxidant coefficient (PAC) was calculated for each infusion. The total phenolic content of medicinal plant infusions ranges from 9 to 2218 mg/L. The FRAP range from 0.06 to 25 mM/L. There was significant linear correlation between total phenolic content and FRAP. According to their antioxidant capacity, 70 medicinal plant extracts can be divided in five groups: (a) very low FRAP (<1 mM/L) n = 9; (b) low FRAP (1–5 mM/L), n = 37; (c) good FRAP (5–10 mM/L), n = 15; (d) high FRAP (10–20 mM/L), n = 8; and (e) very high FRAP (>20 mM/L), n = 1 medicinal plant extract. The PAC was ranging from 1.1 to 3.9 (average 2.4). The best results were obtained for Melissae folium infusions: high phenolic concentration, very high FRAP (>20 mM/L) and PAC > 3. The effect of infusion time and infusion temperature on the phenolic content, FRAP, and free radical scavenging ability was tested. DPPH radical scavenging ability of Melissae folium phenolics was similar to (+)-catechin but not as good as for quercetin. Compared to Trolox and vitamin C, Melissae folium phenolics were more efficient free ABTS radical scavengers. The results indicate that Melissae folium infusions could be an important dietary source of phenolic compounds with high antioxidant capacity comparable with red wine or beverages like tea.     

Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia

The aim of the present work was to investigate and compare phenolic compounds and antioxidant activity of methanol extracts of Quercus robur and Quercus cerris acorn kernels obtained before and after thermal treatment. Content of total phenolics, tannins, non-tannin phenolics and flavonoids was determined spectrophotometrically and content of gallic acid with HPLC. Antioxidant activity of the samples was assayed through FRAP (Ferric Reducing Antioxidant Power), DPPH scavenging test and inhibition of Fe²⁺/ascorbate induced lipid peroxidation. Extracts of native and thermally treated kernels showed high antioxidant activity, with extracts of thermally treated kernels being more active than extracts of native ones. Hydrolysable tannins and gallic acid were identified in all samples. Non-tannin phenolics, including gallic acid, were present in significantly higher quantities in thermally treated samples, whilst tannin content decreased. This indicates that during thermal treatment hydrolysable tannins were degraded. As the result of this degradation and consequent increase of non-tannin phenolics content, and amongst them especially gallic acid, thermally treated samples possess higher antioxidant activity than do the native ones. The obtained results have provided further grounds for establishing Q. robur and Q. cerris acorn kernels as a source for functional food preparation.     

Determination of carnosic acid and rosmarinic acid in sage by capillary electrophoresis

A simple and rapid capillary electrophoresis method was developed for the identification and quantitative determination of two antioxidative compounds – carnosic acid and rosmarinic acid – in the extracts of commercial Sage (Salvia officinalis) tea-bags. Capillary zone electrophoretic separation of carnosic and rosmarinic acids was performed using 40 mmol/l borate, at pH 9.6 as the running buffer. Weighed sage samples were extracted from tea-bags by sonification and the extracts were directly injected without any purification and pre-separation process. Coumarin was used as internal standard for quantitation and the limits of detection for carnosic acid and rosmarinic acid were obtained as 2.79 and 3.18 μg/ml, respectively using UV detection at 210 nm.     

Extraction of phenolics and essential oil from dried sage (Salvia officinalis) using ethanol–water mixtures

Effects of particle size, temperature, contact time, solvent-to-sage ratio and the ethanol–water ratio on the extraction of the active compounds rosmarinic acid, carnosic compounds and essential oil from dried sage (Salvia officinalis) were studied. Optimal extraction conditions giving highest yield of all three active compounds were particle diameter 1 mm, extraction temperature 40 °C, solvent-to-sage ratio of 6:1 and 55–75 wt% ethanol for up to 3 h. This gave an extract equivalent to 14.9% of dry sage, containing 6.9% rosmarinic acid (55% recovery), 10.6% carnosic compounds (75% recovery) and 7.3% essential oil (42% recovery). Scale up of the process by a factor of 100 demonstrated that the optimised laboratory scale process can be carried out without any loss of efficiency at an industrial scale.     

UV-B radiation effects on foliar concentrations of rosmarinic and carnosic acids in rosemary plants

The influence of two different dosages of UV-B radiation on foliar concentrations of rosmarinic and carnosic acids was studied. The results showed that UV-B radiation significantly increased the concentrations of both rosmarinic and carnosic acids, as well as other rosemary compounds, such as naringin and carnosol. However, the increase of rosmarinic and carnosic acid levels were not concomitant with an increase in the DPPH radical-scavenging activity of rosemary extracts from UV-B-treated plants when compared with control plants. The significance of these results is considered.     

Evaluation of the phenolic content,antioxidant activity and colour of Slovenian honey

Honey samples from the seven most common honey types in Slovenia were screened for total phenolic content by the modified Folin–Ciocalteu method, for potential antioxidant activity using the ferric reducing antioxidant power (FRAP) assay and by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method for antiradical activity. In addition the colour characteristics of honey samples were analysed. The results of the study showed that total phenolic content, antioxidant activity and colour parameters differ widely among different honey types. Phenolic content expressed as gallic acid equivalent ranged from 44.8 mg/kg in acacia honey to 241.4 mg/kg in fir honey. Antioxidant activity was the lowest in the brightest acacia and lime honeys and the highest in darker honeys, namely fir, spruce and forest. The colour of the Slovenian honeys, analysed in this study was very variable and ranged from pale yellow to dark brown. Correlations between the parameters analysed were found to be statistically significant (p < 0.05).     

Effect of ionising radiation on polyphenolic content and antioxidant potential of parathion-treated sage (Salvia officinalis) leaves

The γ-irradiation effects on polyphenolic content and antioxidant capacity of parathion-pretreated leaves of Salvia officinalis plant were investigated. The analysis of phenolic extracts of sage without parathion showed that irradiation decreased polyphenolic content significantly (p < 0.05) by 30% and 45% at 2 and 4 kGy, respectively, compared to non-irradiated samples. The same trend was observed for the Trolox equivalent antioxidant capacity (TEAC), as assessed by the anionic DPPH and cationic ABTS radical-scavenging assays. The antioxidant potential decreased significantly (p < 0.01) at 2 and 4 kGy, by 11–20% and 40–44%, respectively. The results obtained with a pure chlorogenic acid solution confirmed the degradation of phenols; however, its TEAC was significantly (p < 0.01) increased following irradiation. Degradation products of parathion formed by irradiation seem to protect against a decline of antioxidant capacity and reduce polyphenolic loss. Ionising radiation was found to be useful in breaking down pesticide residues without inducing significant losses in polyphenols.     

Content of polyphenolic constituents and antioxidant activity of some Stachys taxa

Seven Croatian Stachys taxa (S. alpina, S. officinalis, S. palustris, S. recta subsp. recta, S. recta subsp. subcrenata, S. salviifolia and S. sylvatica) have been investigated in order to determine their content of biologically active compounds (polyphenols, tannins, phenolic acids and flavonoids) as well as their antioxidant activity. All taxa tested had a high content of total polyphenols, medium content of total phenolic acids, and a rather low content of tannins and flavonoids. The total phenolic acids content correlated significantly with total polyphenols content and the content of polyphenols unadsorbed on hide powder. A low correlation between plant phenolic acids and tannins was observed. Methanolic, ethanolic and dichloromethane extracts were investigated using DPPH, lipid peroxidase and xanthine oxidase assays. The extracts showed no inhibitory effects against lipid peroxidation and xanthine oxidase, but they had the ability to scavenge DPPH. The most effective in the DPPH assay were methanolic extracts of S. recta sub. recta and S. palustris whose radical scavenging activity was higher then that of the reference rutin. A low correlation between radical scavenging capacities of extracts with total flavonoids content was observed. The results indicate that investigated Stachys taxa exhibit potent antiradical activity and therefore could be a potential material for extracting free radical scavengers.     

Chemical composition and antioxidant activities of Myrtus communis L. berries extracts

Myrtle (Myrtus communis L.) berries extracts were prepared with solvents at different polarity (water, ethanol, and ethyl acetate) and analysed using different in vitro tests in order to evaluate their antioxidant properties. Antiradical and total antioxidant activities were measured with DPPH and FRAP tests, respectively. Their ability to protect biological molecules was assessed using the cholesterol and LDL oxidation assays. In addition, phenolic compounds and unsaturated fatty acids composition was analysed by HPLC–DAD and HPLC–MS/MS. Ethanol and water extracts showed the highest amount of extracted compounds, but the highest antiradical and antioxidant activities were found in ethanol and ethyl acetate extracts. These extracts were also the ones with the highest content of phenolic compounds. In addition, our results showed a highly significant correlation between the amount of total phenols and antiradical (R² = 0.9993) or antioxidant activities (R² = 0.9985) in these extracts. HPLC–DAD and HPLC–MS analyses showed significant quantitative and qualitative differences among these three extracts. The ethyl acetate extract had the highest protective effect in assays of thermal (140 °C) cholesterol degradation and Cu²⁺-mediated LDL oxidation, inhibiting the reduction of polyunsaturated fatty acids and cholesterol, and the increase of their oxidative products. These results suggest that because of these properties, myrtle berries could be used in dietary supplements preparations or as food additives.     

Development of a reversed-phase high performance liquid chromatography (RP-HPLC) procedure for the simultaneous determination of phenolic compounds in peanut skin extracts

A reversed-phase high performance liquid chromatography (RP-HPLC) procedure was developed for simultaneous determination of five phenolic acids, two stilbenes and eight flavonoids in peanut skin extract. A C₁₈ column fitted with diode array detection at 250 and 320, 280 and 370, and 306 nm for phenolic acids, flavonoids and stilbenes, respectively, with mobile phase consisting of 0.1% formic acid in water and 0.1% formic acid in 100% acetonitrile. Phenolic compounds were eluted with good resolution (Rs > 1.5) within 95 min as follows: gallic, protocatechuic, epigallocatechin, catechin, β-resorcylic (internal standard), caffeic, procyanidin B₂, epicatechin, epigallocatechin gallate, p-coumaric, ferulic, piceid, epicatechin gallate, catechin gallate, resveratrol and quercetin. The variation in recovery and reproducibility in peak area was <11 and <2.5%, respectively. The correlation coefficients, r, of calibration curves of the 15 compounds were >0.999. The method was used to quantify phenolic compounds in peanut skin extracts from Runner, Virginia and Spanish peanuts.     

Determination of free phenolic acids and antioxidant activity of methanolic extracts obtained from fruits and leaves of Chenopodium album

In this study, determination of phenolic acids as well as investigation of antioxidant activity of methanolic extracts from the fruits and leaves of Chenopodium album is described. Extracts were subjected to acidic hydrolysis in order to obtain total free phenolic acids. However, some of phenolic acids were identified and quantified by HPLC-DAD. The results were confirmed by LC-MS equipped with MS-ESI. In addition, Folin–Ciocalteu method was applied to determine the total phenolic contents. The antioxidant activity of C. album extracts was examined by using DPPH and hydroxyl radical-scavenging activity assays. Results revealed that the leaves extract exhibits better performance in antioxidant assays and in the higher total phenolic contents (3066 mg of GAE/100 g) when compared to fruits extract (1385 mg of GAE/100 g). From these results it has been revealed that the methanolic extracts of C. album from fruits and leaves have great potential as a source for natural health products.     

Composition of flavonoids and phenolic acids in Glycin tomentella Hayata cultivated in various soils

A high-performance liquid chromatography (HPLC) method was developed to simultaneously separate 12 phenolic acids and 21 flavonoids. The separation was performed with a C₁₈ column and a binary gradient solvent system consisting of methanol and water with 9% glacial acetic acid. The peak resolutions (Rs) were 0.51–12.41 and separation factors (α) were all higher than 1. The method was used to survey these phenolic components in Glycin tomentella Hayata. Diadzein was the major flavonoid in the leaves and roots, and gentisic acid and ferulic acid were the major phenolic acids in the leaves. Amounts of phenolic acids and flavonoids in the leaves from varied soil cultivations were in the order: loam > sand > red loamy sand. Flavonoid amounts in the roots also showed the same trend; however, phenolic acid amounts were low and did not present significant differences. Overall, the roots had much higher phenolic contents than the leaves.     

Variations in phenolic composition and antioxidant properties among 15 basil (Ocimum basilicum L.) cultivars

In this study, the influences of cultivar on the phenolic composition and antioxidant properties of 15 different basil varieties was determined. Cultivar had a statistically significant effect on total phenolic levels (p < 0.001) and anthocyanin concentrations (p < 0.001). Analysis of individual phenolic acid levels by high-performance liquid chromatography showed substantial variations in the phenolic acid profiles among cultivars. Rosmarinic (p < 0.001), chicoric (p = 0.002) and caffeic (p = 0.001) acid concentrations were affected by cultivar, although caftaric acid levels (p = 0.083) were not. Nine of the cultivars in this study contained chicoric acid in higher concentrations than rosmarinic acid. These are the first basil cultivars that have been identified in which rosmarinic acid is not the dominant phenolic acid. In addition, six of the cultivars in this study had caftaric and caffeic acid concentrations that were similar or higher than rosmarinic acid levels. Cultivar also had a significant impact on both FRAP (ferric reducing antioxidant power, p = 0.007) and DPPH (2,2′-diphenyl-1-picrylhydrazyl, p = 0.004) antioxidant capacities. For the basil cultivars in this study, the individual phenolic acid composition was found to be an important factor influencing the measured antioxidant capacity.     

Influence of technological processes on phenolic compounds,organic acids,furanic derivatives,and antioxidant activity of whole-lemon powder

The healthy properties of citrus fruits have been attributed to ascorbic acid and phenolic compounds, mainly to flavonoids. Flavonoids are important phytonutrients because they have a wide range of biological effects that provide health-related properties. In this context, this study seeks to characterise the phenolic compounds in lemon and their stability in different drying processes (freeze-drying and vacuum-drying) and storage conditions (−18 and 50 °C for 1 and 3 months). A powerful high-performance liquid chromatography coupled to DAD and electrospray-ionization time-of-flight mass spectrometry (HPLC–ESI-TOF-MS) method has been applied for the separation, identification, and quantification of 19 phenolic compounds and 4 organic acids. To our knowledge, two hydroxycinnamic acids have been identified for the first time in lemon. Folin–Ciocalteu was applied to determine total phenolic compounds and TEAC, FRAP, and ORAC were applied to determine the antioxidant capacity of lemon. Total phenolic content significantly differed in the samples analysed, vacuum-dried lemon showing the highest phenolic content, followed by freeze-dried lemon and, finally, vacuum-dried lemon stored at 50 °C for 1 and 3 months. The content in furanic compounds was determined to evaluate the heat damage in lemon and it was showed an increase with the thermal treatment because of the triggering of Maillard reaction. As exception of ORAC, antioxidant-capacity assays were not correlated to phenolic content by HPLC due to the formation of antioxidant compounds during Maillard reaction.     

Non-toxic Salvia sclareoides Brot. extracts as a source of functional food ingredients: Phenolic profile,antioxidant activity and prion binding properties

Salvia sclareoides is an aromatic herb native to Portugal, of which phenolic content (Folin–Ciocalteau method), chemical profile (HPLC/DAD), antioxidant activity (DPPH, β-carotene/linoleic acid assays), acute toxicity (MTT method, adapted for non-adherent cells), genotoxicity (short-term chromosomal aberration assay) and prion binding properties were evaluated in the acetone, water, ethanol, methanol and n-butanol extracts. The latter presented the highest phenolic content and antioxidant activity (DPPH assay), and was the single one with the flavonoids (+)-catechin, kaempferol O-glucoside and quercetin. Vanillic acid was the major component of all extracts but gallic, gentisic, caffeic, syringic, coumaric and ferulic acids were also found in some extracts. Only the n-butanol extract had components binding to the cellular form of human prion protein detected by NMR which showed specificity for two regions of the folded domain and for the unstructured N-terminal region. Extracts were not cytotoxic nor genotoxic, reinforcing the potential of S. sclareoides for nutraceutical purposes.     

Potassium rate alters the antioxidant capacity and phenolic concentration of basil (Ocimum basilicum L.) leaves

In the current study, we have determined how potassium rate affects the phenolic levels and antioxidant properties of three cultivars of basil (Ocimum basilicum L.) leaves: Dark Opal, Sweet Thai, and Genovese. Potassium rate increased the total phenolic concentration in basil, with basil treated at the highest potassium rate, 5.0 mM K, containing greater phenolic levels than basil treated at the lowest potassium rate, 1.0 mM K (p = 0.008). Basil grown at 5.0 mM K also had higher concentrations of rosmarinic (p = 0.005) and chicoric (p < 0.001) acids compared to lower potassium treatment levels. Correspondingly, 1.0 mM K basil had lower DPPH (2,2′-diphenyl-1-picrylhydrazyl) (p ? 0.005) and FRAP (ferric reducing antioxidant power, p = 0.043) antioxidant capacities compared to basil treated at higher potassium rates. Cultivar was also found to impact the phenolic composition and antioxidant properties of basil, with Sweet Thai having lower total phenolic concentrations and FRAP antioxidant capacities than Dark Opal and Genovese. Although not affected by potassium rate, anthocyanin concentrations varied significantly among the cultivars, with purple Dark Opal basil exhibiting higher anthocyanin levels than Sweet Thai (p = 0.003) and Genovese (p = 0.002).