Raimondas Raudonis

Comparative evaluation of post-column free radical scavenging and ferric reducing antioxidant power assays for screening of antioxidants in strawberries.

ABTS and FRAP post-column techniques evaluate the antioxidant characteristics of HPLC separated compounds with specific reagents. ABTS characterize their ability to scavenge free radicals by electron-donating antioxidants, resulting in the absorbance decrease of the chromophoric radical. FRAP - is based on the reduction of Fe(III)-tripyridyltriazine complex to Fe(II)-tripyridyltriazine at low pH by electron-donating antioxidants, resulting in an absorbance increase. Both post-column assays were evaluated and compared according to the following validation parameters: specificity, precision, limit of detection (LoD), limit of quantitation (LoQ) and linearity. ABTS and FRAP post-column assays were specific, repeatable and sensitive and thus can be used for the evaluation of antioxidant active compounds. Antioxidant active compounds were quantified according to TEAC for each assay and ABTS/FRAP ratio was derived. No previous records of antioxidative activity of leaves and fruits of strawberries (Fragaria viridis, Fragaria moschata) research have been found. The research results confirm the reliability of ABTS and FRAP post-column assays for screening of antioxidants in complex mixtures and the determination of radical scavenging and ferric reducing ability by their TEAC values.

Optimization and validation of post-column assay for screening of radical scavengers in herbal raw materials and herbal preparations

On-line method, which combines HPLC distribution and post-column reaction, was designed for the search of individual antioxidants. Optimization of the assay was performed evaluating optimal ABTS(+) radical cation concentration in the reactor, reaction time, impact of flow rate, reaction coil length. HPLC-ABTS assay validation in this work was performed by assessing reference antioxidant negative peak areas in radical scavenging chromatogram. Sample free radical scavenging activity is expressed as trolox equivalent antioxidant capacity (TEAC). Optimized and validated method was applied in detection of compounds possessing free radical scavenging ability in complex mixtures. Antioxidant compounds were studied in perilla (Perilla frutescens (L.) Britton var. crispa f. viridis) herbal raw material and its preparations. The HPLC-separated antioxidant compounds were identified using HPLC-photodiode array coupled to mass spectrometer, using a reference mass for determining accurate masses. Radical scavenging characteristics of rosmarinic acid, which is the dominant phenolic compound in medicinal herbal raw material of perilla and its preparations, were confirmed by the calculated TEAC values. Compounds responsible for antioxidant effect in herbal raw materials and herbal preparations were identified, evaluated and compared.

Phenolic Composition and Antioxidant Activity of Malus domestica Leaves

The aim of this study was to determine the composition and content of phenolic compounds in the ethanol extracts of apple leaves and to evaluate the antioxidant activity of these extracts. The total phenolic content was determined spectrophotometrically, as well as the total flavonoid content in the ethanol extracts of apple leaves and the antioxidant activity of these extracts, by the ABTS, DPPH, and FRAP assays. The highest amount of phenolic compounds and flavonoids as well as the highest antioxidant activity was determined in the ethanol extracts obtained from the apple leaves of the cv. Aldas. The analysis by the HPLC method revealed that phloridzin was a predominant component in the ethanol extracts of the apple leaves of all cultivars investigated. The following quercetin glycosides were identified and quantified in the ethanol extracts of apple leaves: hyperoside, isoquercitrin, avicularin, rutin, and quercitrin. Quercitrin was the major compound among quercetin glycosides.

A Comparative Study of Phenolic Content in Apple Fruits

The ethanol extracts of apple fruits harvested from the cultivars Aldas, Auksis, Ligol, and Lodel grown in Lithuania were analyzed by the high-performance liquid chromatography method. Chlorogenic acid was found to be a predominant component in the apple fruits of all the cultivars, except the cultivar Ligol. (–)-Epicatechin was the major compound in the ethanol extracts of apple fruits obtained from all the cultivars, while the amount of (+)–catechin was lower. The following quercetin glycosides were identified and quantified: hyperoside, isoquercitrin, avicularin, rutin, and quercitrin. Hyperoside was the major quercetin glycoside in apple fruits.

Phytochemical and antioxidant profiles of leaves from different Sorbus L. species

Leaves of Sorbus L. have been used in various traditional medicine systems. Phenolic compounds determine the main pharmacological effects of Sorbus L. In this study, phytochemical and antioxidant profiles of Sorbus anglica, Sorbus aria, Sorbus arranensis, Sorbus aucuparia, Sorbus austriaca, Sorbus caucasica, Sorbus commixta, Sorbus discolor, Sorbus gracilis, Sorbus hostii, Sorbus semi-incisa and Sorbus tianschanica were determined. Twenty four constituents were identified in Sorbus L. species using ultra high performance liquid chromatography coupled to quadruple and time-of-flight mass spectrometers. Post-column FRAP assay identified compounds with reducing activity and revealed significantly greatest total antioxidant activity of 175.30 μmol TE/g DW, 169.20 μmol TE/g DW and 148.11 μmol TE/g DW in S. commixta, S. discolor and S. gracilis leaf samples, respectively, with neochlorogenic and chlorogenic acids being most significant contributors. Characteristic fingerprints of phytochemical and antioxidant profiles could be applied for the quality evaluation of various raw materials of Sorbus L. species.

Phenolic and antioxidant profiles of rowan (Sorbus L.) fruits

Fruits of different Sorbus L. species have been traditionally used in food production and in the treatment of various ailments. Besides common antioxidant active phytochemicals such as ascorbic acid, tocopherols and carotenoids, fruits are rich in phenolic compounds that are of particular interest. In this study, profiles of separate antioxidant active compounds (reducing and radical-scavenging activities) were investigated using online assays with post-column reactions. Significant variations in phenolic acids and flavonoids contents and antioxidant activity values were observed in the fruits of Sorbus L. species studied. Neochlorogenic and chlorogenic acids were determined as markers of antioxidant activity. Characteristic patterns of antioxidant profiles obtained using HPLC post-column FRAP and ABTS assays significantly depend on specific Sorbus L. species and are suitable for equivalency research of Sorbus L. fruits.

Application of an Optimized HPLC Method for the Detection of Various Phenolic Compounds in Apples from Lithuanian Cultivars

A specific analytical procedure including sample preparation and HPLC analysis was developed and validated for the detection of phenolic compounds in the samples of different apples from popular Lithuanian cultivars “Aldas,” “Auksis,” “Ligol,” and “Sampion.” The conditions for phenol extraction were optimized: the solvent of the extraction was 70% (v/v) ethanol, and the extraction was performed in an ultrasound bath for 20 min at the temperature of 40°C. The HPLC mobile phase consisted of 2% (v/v) acetic acid in water and 100% (v/v) acetonitrile. Using the HPLC technique, 11 analytes were identified, and their specificity was confirmed: procyanidin B1, (

Improving the Extraction of Juice and Anthocyanin Compounds from Blueberry Fruits and Their by-Products by Pulsed Electric Fields

The aim of the study was to investigate the influence of PEF pre-treatment (1, 3, 5 kV/cm and 10 kJ/kg) of blueberry fruits on the extraction yield, anthocyanins content and antioxidant activity of the juice obtained by pressing (1.32 bar for 8 min). Additionally, the extraction with solvent of anthocyanins from the berry by-products (pressed cakes) was also evaluated. Blueberry juice obtained from PEF treated berries at 1 and 3 kV/cm showed the highest increase in juice yield (+32%), total anthocyanins content (+55%) and DPPH-RSC (+ 40%), compared with the untreated sample. The extracts from press cakes obtained after PEF assisted-pressing of berry fruits showed a significant higher content of total anthocyanins (+95%) and DPPH-RSC (+138%) when compared with the control sample. The higher the field strength applied the greater the recovery of antioxidant compound in the extracts. Significant differences in the contents of anthocyanin glycosides were detected between blueberry juice and press cake extracts. The results obtained from this study demonstrate that PEF-assisted pressing is promising for production of higher quality juices and for the valorization of berry by-products.

Quality evaluation of different preparations of dry extracts of birch (Betula pendula Roth) leaves

Qualitatively prepared dry extracts are advantaged over conventional fluid extracts. Extracts of Betula pendula Roth leaves possess mild diuretic effects and anti-inflammatory activity. In this work, the spray-drying and lyophilisation processes were evaluated for producing dry extracts of birch leaves. The purpose was to identify the best drying method that provides the highest content of phenolic compounds and possesses greatest antioxidant activity. Predominant compounds hyperoside and chlorogenic acid were chosen as markers for the quantitative control of phenolic compounds. Their determined amounts in hydroalcoholic birch leaf extract were 15.85 and 8.77 mg/g of dry residue, respectively. Insignificant differences were determined in spray- and freeze-dried extracts. In the antioxidant profile, hyperoside (28.9 μmol TE/g dw) and chlorogenic acid (22.8 μmol TE/g dw) possessed strongest ferric-reducing activity. Also, no significant differences of antioxidant activity were determined in the spray- and freeze-dried extracts.

Chlorogenic acid, rutin and hyperoside content in Fragaria vesca, F. viridis and F. moschata in Lithuania

In Lithuania, two species of the genus Fragaria L. (Rosaceae), F. vesca L. and F. viridis Weston, occur naturally in the wild and two others, F. moschata Weston and F. × ananassa Duchesne ex Rozier are found escaped from cultivation. The main objective of this study was to establish the variation pattern in the content of chlorogenic acid, rutin and hyperoside in leaves and fruits of the native Lithuanian species. In this work, the chemical polymorphisms of different Fragaria species were studied by growing plants side by side under the same cultivated field conditions. F. vesca fruits had the highest rutin (1.38  ±  0.19 mg g − 1 DM), hyperoside (0.69  ±  0.10 mg g−1 DM) and chlorogenic acid (2.25  ±  0.34 mg g−1 DM) content, followed by F. viridis and F. moschata. Our results showed that the leaves should be taken into account as important rutin and hyperoside contributors for strawberries.