Serbian aromatized wine “Bermet”: Electrochemical, chemiluminescent and spectrophotometric determination of antioxidant activity

Serbian aromatized wine “Bermet” from grapes grown on Fruška Gora Mountain has been in production since the 15th century. Ten commercial Bermets produced according to the traditional procedure by different manufacturers, and six prepared within the scope of this study were assessed for antioxidant (AO) activity using electrochemical, chemiluminescent and spectrophotometric AO assays. Direct current polarographic assay based on the decrease of anodic current of [hydrogen(peroxido)(1-)]hydroxidomercury(II) complex formation in alkaline H2O2 solution at potential of mercury oxidation, chemiluminescent H2O2 scavenging assay, as well as commonly used spectrophotometric assays (2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) based Trolox equivalent antioxidant capacity (TEAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP)) were used. Total phenolic content (TPC) was determined by Folin–Ciocalteu assay. The results obtained were correlated using regression analysis, ANOVA and F-test. An integrated approach to AO capacity determination allowed a more comprehensive comparison between samples. The approach is based on the introduction of the relative antioxidant capacity index, calculated by assigning each AO assay equal weight, and by PCA analysis. In addition, the introduction of phenolic antioxidant coefficients, calculated as the ratio between individual AO capacity and TPC, enabled a better understanding of their relation

Antioxidant Capacity of Nettle Leaves During Osmotic Treatment

Osmotic treatment (OT) of nettle leaves was assessed in various osmotic solutions (sugar beet molasses – SBM and ternary aqueous solution – TAS), at temperatures of 20, 35 and 50 °C, under the atmospheric pressure. The influence of the kind of utilized osmotic solution, process temperature and osmotic time on the antioxidant activity (AOC), expressed with the spectrophotometric assays (ABTS, FRAP and DPPH), as well as two direct current polarographic assays, Hydroxo Perhydroxo Mercury (II) complex assay, based on the decrease of anodic current and assay based on the decrease of a cathodic current of Hg (II) reduction. For determination of the total phenolic content Folin-Ciocalteu assay was used. The Relative Antioxidant Capacity Index (RACI), obtained by setting equal weight for every involved assay was applied in order to get an extensive comparison among analyzed samples and between the used assays. Based on these results, after the OT of nettle leaves in TAS, the AOC decreased, while the OT in SBM increased AOC values. The phenolic antioxidant coefficients (PAC), calculated as the ratio between particular AO capacity and TPC, were used to achieve a more comprehensive comparison between analysed samples, as well as applied assays. The results of RACI evaluation revealed that the most favorable osmotic treatment is the one performed for 5h at 35 °C

New herbal bitter liqueur with high antioxidant activity and lower sugar content: innovative approach to liqueurs formulations

Herbal liqueurs are spirits with numerous functional properties, due to the presence of bioactive extractable compounds deriving from herbs. The aim of this study was to obtain new herbal bitter liqueur (HBL) on the basis of twelve selected bitter and aromatic plants extracts, with an optimal sensory profile for consumer acceptance. Also, the determination of optimal sugar content in HBL was done. Furthermore, antioxidant (AO) capacity and total phenolic content (TPC) of HBL was evaluated and compared to similar commercial herbal spirits. Among five tested formulations, assessed by 9-point hedonic scale, HBL with the ratio of bitter and aromatic plants 1:4 was the most acceptable. Ideal concentration of sugar in HBL, determined using a just-about-right scale, was found to be 80.32 g/l of sucrose, which is approximately 20% less than the minimum stipulated by European Union Regulation and several times lower than in the majority of commercial liqueurs. Obtained result indicates the possibility of sugar reduction in liqueurs, and suggests the need to carry out sensory analysis before production of these high-calorie beverages. Radical scavenging ability against DPPH and ABTS radicals, as well as ferric reducing antioxidant power and TPC of HBL were convincingly superior in comparison to similar commercial herbal alcoholic beverages. High correlation coefficients between TPC and other assays applied strongly support the significant role of the polyphenols in the total AO capacity of the HBL and other tested commercial herbal spirits. Headspace GC/MS revealed that the most abundant terpenes were menthone (3.75%), eucalyptol (3.42%) and menthol (3.10%), whereas methanol was present in a small amount (4.97 mg/l)

Environmental effects on associations among nitrogen use efficiency traits in wheat

Nitrogen use efficiency parameters of twelve bread wheat cultivars were studied in nine environments comprised of three nitrogen applications tested over three years. An environment-by-trait association biplot and a trait-association by environment biplot were applied to understand environmental effects on these traits and relationships among them. The following trait associations were relatively stable across environments: negative associations of straw nitrogen content vs. nitrogen remobilization efficiency, straw nitrogen content vs. nitrogen harvest index and a positive association of nitrogen remobilization efficiency vs. nitrogen harvest index. The selection of genotypes with a high nitrogen harvest index and nitrogen remobilization efficiency could be used in the development of cultivars with desired nitrogen use efficiency. A low straw nitrogen content can also be used as a reliable and cost-effective indicator in the selection of genotypes with high nitrogen use efficiency

Modification of DC polarographic antioxidant assay—Application to aromatic plants and their active principles

A direct current (DC) polarographic assay based on the decrease of anodic current of HydroxoPerhydroxoMercury (II) Complex (HPMC) formation in H2O2 solution in Clark Lubs (CL) buffer (pH 9.8) as working solution was previously applied to determine antioxidant (AO) capacity of water‐soluble compounds. Here, the applicability of HPMC assay was extended into samples poorly soluble in water such as the essential oils and extracts of Lamiaceae and Apiaceae species obtained by ultrasound‐assisted maceration (UAM) and Soxhlet extraction (SE) with 70 and 96% ethanol as well as individual compounds present. The influence of solvents miscible with water on HPMC anodic current was studied, and working solution was optimized. A modified HPMC method was applied to measure AO capacity of essential oils and extracts as well as compounds identified using gas chromatography‐mass spectrometer (GC‐MS) and gas chromatography with flame‐ionization detection (GC‐FID) (terpenoids and catechols) or known to be present (phenolic acids and flavonoids). A 1:1 mixture of CL buffer and ethanol was chosen as working solution. AO capacity of essential oils and extracts, established by modified HPMC assay, was in range of 1.2‐2.0 and 9.2‐38.4 (%/mL) while terpenoids and phenolics in range of 0.1‐0.5 and 13.5‐38.5 (%/mol), respectively. The superior AO capacity was ascribed to essential oils and extracts of Lamiaceae species and to extracts obtained with 70% ethanol. A higher AO capacity of extracts in comparison to essential oils was corroborated with a difference in phenolics and terpenoids capacity

Antioxidant Capacity Determination of Complex Samples and Individual Phenolics - Multilateral Approach

Antioxidant (AO) capacity of various medicinal plants extracts and phenolic compounds was assessed by the most widely used spectrophotometric assays such as ferric reducing antioxidant power (FRAP) and scavenging of 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH). In addition, two direct current (DC) polarographic assays, one based on a decrease of anodic current of [Hg(O2H)(OH)]-HydroxoPerhydroxoMercury(II) Complex (HPMC) formation in alkaline solution of H2O2, at the potential of mercury dissolution and another recently developed Mercury Reduction Antioxidant Power (MRAP), based on a a decrease of cathodic current of Hg(II) reduction were employed. Percentage of both currents decrease was plotted versus the volume of gradually added complex samples or the amount of individual ones and the slopes of these plots were used to express AO capacity. Total phenolic content (TPC) of extracts was determined by Folin-Ciocalteu (FC) assay. Correlations between applied assays were calculated by regression analysis. Relative Antioxidant Capacity Index (RACI), calculated by assigning equal weight to all applied assays and Phenolic Antioxidant Coefficients (PAC), calculated as a ratio between particular AO capacity and TPC, were used to achieve more comprehensive comparison between analyzed samples, as well as applied assays

Evaluation of novel green walnut liqueur as a source of antioxidants: Multi-method approach

In this study, a novel green walnut liqueur (GWL) based on green walnuts, as the main ingredient, with the addition of fruits, aromatic plants, chocolate and honey, was produced at the pilot-scale. Antioxidant activity (AO) of the obtained GWL was determined using multiple AO assays in parallel, standard spectrophotometric (FC, DPPH and FRAP) and recently developed electrochemical ones, HydroxoPerhydroxoMercury(II) Complex and Mercury Reduction Antioxidant Power, and compared to similar commercial alcoholic beverages. Characterization of the GWL in terms of volatile and polyphenolic components was performed using SPE-GC-MS and HPLC-DAD-MS/MS, respectively. Sensory quality assessment was performed by experts in the field of sensory analysis of alcoholic beverages, using a scoring method. According to all AO assays applied, AO activity and total phenolics content of GWL were superior in comparison to commercial spirits considered. The volatile fraction of GWL was mainly composed of eugenol,alpha-terpineol and vanillin, while the most prevalent phenolic compounds were gallic (5.054 mg/L) and chlorogenic acid (1.307 mg/L) and flavonoids such as catechine (0.882 mg/L), quercetin (0.499 mg/L) and its sugar-conjugated derivatives, quercetin 3-O-glucoside (0.774 mg/L) and quercetin-3-O-rhamnoside (0.614 mg/L). Gallic acid is the major contributor to total AO activity, especially determined by DPPH and FRAP, followed by catechine, quercetin and chlorogenic acid. Among the terpenoids, contribution of eugenol to total AO activity is estimated as the highest. Excellent sensory quality (18.52 of maximum 20 scores) was ascribed to GWL. Consequently, the presence of bioactive compounds and high AO activity of GWL, in addition to high sensory quality score, indicates a high market potential for this high-value product

Antioxidant activity of propolis extracts from Serbia: A polarographic approach

Antioxidant activity (AO) of commercial propolis extracts (PEs), available on Serbian market, was determined by direct current (DC) polarography. Polarographic anodic current of 5.0 mmol L-1 alkaline solution of H2O2 was recorded at potentials of mercury dissolution. Decrease of the current was plotted against the volume of gradually added PEs. The volume of PE causing 20% current decrease was determined from the linear part of the plot. Antioxidant activity was expressed in H2O2 equivalent (HPEq), representing the volume of PE that corresponds to 1.0 mmol L-1 H2O2 decrease. Resulting HPEq ranged between 1.71 +/- 0.11 and 8.00 +/- 0.18 mu L. Range of 1,1-dipheny1-2-picryl hydrazyl (DPPH) radical scavenging activity was from 0.093 +/- 0.004% to 0.346 +/- 0.006%. Total phenolic content (TCP) of PE with superior AO activity was 5.31 +/- 0.05%g GAE, while the extract with the lowest activity contained 1.45 +/- 0.02%g GAE. Antioxidant activity, determined by polarographic method, was correlated with DPPH scavenging activity (R-2 = 0.991) and TCP (R-2 = 0.985). Validity of obtained results was further confirmed using ANOVA and post hoc Tukey HSD test