Pranas Viškelis

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.

Phytochemical composition, antioxidant and antimicrobial properties of raspberry fruit, pulp, and marc extracts

In this study, the phytochemical composition (total phenolics, total anthocyanins and ellagitannins) and antimicrobial properties of raspberry fruit, pulp, and marc extracts obtained with 80% methanol and 80% acetone from different plant cultivars were assessed. The extracts were also subjected to screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) assay. The content of total phenolics in berry pulp extracts varied from 20.4 to 35.5, in whole berry extracts from 43.6 to 83.1 and in berry marc extracts from 93.9 to 163.8 mg/g (dry weight of extract). The content of ellagitannins was higher by 63–80% in raspberry marc extracts than in pulp extracts. Raspberry fruit, pulp and marc extracts isolated with aqueous acetone possessed stronger antimicrobial activity than the corresponding extracts isolated with aqueous methanol. The highest inhibitory effect against the investigated Gram-positive bacteria and yeast strains was shown by the extracts isolated from raspberry marc and containing the highest concentrations of total phenolics and ellagitannins.

Optimization of application of nitrogen fertilizers to increase the yield and improve the quality of Chinese cabbage heads

Abstract The study investigates the effects of nitrogen fertilizers on the characteristics of the autumn crop of Chinese cabbage. The rates applied varied from 0 to 225 kg ha−1 (N0, N45, N90, N135, N180, N225); the supply of phosphorus and potassium fertilizers was similar in the all trials, 90 and 150 kg ha−1, respectively. It was found that the optimum nitrogen fertilization rate for the autumn crop of Chinese cabbage was N135. In the case of lower nitrogen rates the yield decreased and the cabbage heads were smaller. Further increase in fertilizer rate (>N135) resulted in a higher percentage of non-standard cabbage heads, while the yield remained almost unchanged compared with N135. The total plant mass of cabbage crop fertilized with N135 was 76 t ha−1; plant residues constituted 33 t ha−1 (43% of the total mass). The yield of market quality cabbage heads was 30 t ha−1 (70% of all the heads produced); the rest of heads were loose, not formed or rot-infected. The optimal amount of total mineral nitrogen (the sum of nitrogen present in the 0–60 cm soil layer and the nitrogen supplied with fertilizers) before planting was 260 kg ha−1. When nitrogen rates were higher than N180 the quality of cabbage heads in terms of the content of vitamin C, nitrates, soluble solids, total solids and sugars decreased.

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.

Fermentation Processes Using Lactic Acid Bacteria Producing Bacteriocins for Preservation and Improving Functional Properties of Food Products

During the recent years health-conscious consumers are looking for natural foods without chemical preservatives that will fit in their healthy lifestyle. The increasing consumption of precooked food, prone to temperature abuse, and the import of raw foods from developing countries are among the main causes of this situation. Biopreservation refers to extended shelf life and enhanced safety of foods using microorganisms and/or their metabolites (Ross et al., 2002). LAB is generally employed because they significantly contribute to the flavor, texture and, in many cases, to the nutritional value of the food products (McKay and Baldwin, 1990). LAB are used as natural or selected starters in food fermentations and exert the antimicrobial effect as a result of different metabolic processes (lactose metabolism, proteolytic enzymes, citrate uptake, bacteriophage resistance, bacteriocin production, polysaccharide biosynthesis, metal-ion resistance and antibiotic resistance) (Zotta, T., 2009; Corsetti, 2004). Lactic acid bacteria (LAB) play a key role in food fermentations where they not only contribute to the development of the desired sensory properties in the final product but also to their microbiological safety. LAB has a GRAS status (generally recognized as safe) and it has been estimated that 25% of the European diet and 60% of the diet in many developing countries consists of fermented foods (Stiles, 1996). Fermentation is one of the most ancient and most important food processing technologies. Fermentation is a relatively efficient, low energy preservation process, which increases the shelf life and decreases the need for refrigeration or other forms of food preservation technology. Currently, fermented foods are increasing in popularity (60% of the diet in industrialized countries) and, to assure the homogeneity, quality, and safety of products, they are produced by the intentional application in raw foods in different microbial systems (starter/protective cultures) (Holzapfel et al., 1995).

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, (

Biochemical and agro-biological diversity of Viburnum opulus genotypes

Interest in the biochemical composition of Viburnum opulus fruit has intensified due to the food industry’s demand for natural vitamins, pigments and other substances that enhance the value of different foods. The present study was conducted to determine the agro-biological and biochemical variability of V. opulus and to select the genotypes that could best serve as sources of health promoting substances. Twelve selected genotypes were evaluated. ‘Leningradskaya Otbornaya’, V. opulus var. americanum, ‘Zarnitsa’, and local clone P2 were determined to be the best genotypes for growth in commercial plantations. Fruits of the local clone P3 were characterised by large amounts of total phenolics, ascorbic acid, and reducing sugars. V. opulus var. sargentii and V. opulus var. americanum contained exceptionally large amounts of total phenolics, 1460.0 and 1400.0 mg/100 g, respectively. The amount of ascorbic acid varied from 12.4 to 41.4 mg/100 g, the amount of carotenoids varied from 1.4 to 2.8 mg/100 g, the amount of anthocyanins varied from 23.2 to 44.6 mg/100 g, and the amount of total phenolics varied from 753.0 to 1460.0 mg/100 g. The presence of these large amounts of biologically active compounds enables their use as potent antioxidants. The data describing agro-biological characteristics, biochemical components, and health promoting activities of V. opulus fruits will increase the understanding of this plant and facilitate its use in the food and pharmaceuticals industry.

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.