Papers by Nadezhda Petkova
The current research is dedicated to following the accumulation of prebiotics inulin and fructool... more The current research is dedicated to following the accumulation of prebiotics inulin and fructooligosaccharides in the roots of Bulgarian medicinal plants common chicory (Cichorium intybus L.), dandelion (Taraxacum officinale Web.) and meadow salsify (Tragopogon pratensis L.) in some areas of the Bulgaria for a period of two years. The roots of each plant were subjected to exhausting ethanol and subsequent water extraction. The contents of inulin-type fructans in the obtained extracts have been determined by a spectrophotometric method based on resorcinol reaction and TLC analysis. It has been found that the amounts of fructooligosaccharides and inulin were the highest in roots of the plants collected in the autumn season as in taproots of common chicory reached to 23 g/100 g dw and up to 34 g/100 g d.w in dandelion roots, respectively. The underground parts of the studied medicinal plants collected in the spring have been characterized by very high levels of fructo-oligosaccharides and sugars. Meadow salsify showed relatively constant levels of fructans in its taproots (18 g/100g d.w).
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Journal of Central European Agriculture, 2021
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Journal of Apicultural Science
Propolis (bee glue), a valuable biological mixture produced by European honey bees (Apis mellifer... more Propolis (bee glue), a valuable biological mixture produced by European honey bees (Apis mellifera L.), is widely used as a remedy in traditional and alternative medicine, as an effective food biopreservative and as a nutritional value enhancer. The present study aimed to investigate eighty propolis samples collected from all twenty-eight districts of Bulgaria in the period of 2020–2022 in order to determine their physicochemical properties as well as their antioxidant and antimicrobial potential. The raw propolis samples exhibited brown or green colour depending on the climatic zone from which they are collected and pH values from 4.82 to 5.87, while the moisture content ranged between 0.98% and 2.97%. The total phenolics content (TPC) and total flavonoids content (TFC) varied from 63.14 mg GAE/g to 737.27 mg GAE/g, and from 29.22 mg QE/g to 234.17 mg QE/g, respectively. The propolis samples demonstrated significant antioxidant potential determined by DPPH and FRAP methods, from 18...
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Journal of Essential Oil Bearing Plants
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Journal of Fungi
The aim of this study is to characterize the bioactivity of mycelial biomass and crude exopolysac... more The aim of this study is to characterize the bioactivity of mycelial biomass and crude exopolysaccharides (EPS) produced by Trametes versicolor NBIMCC 8939 and to reveal its nutraceutical potential. The EPS (1.58 g/L) were isolated from a culture broth. The macrofungal biomass was rich in protein, insoluble dietary fibers and glucans. The amino acid composition of the biomass was analyzed and 18 amino acids were detected. Three mycelial biomass extracts were prepared and the highest total polyphenol content (16.11 ± 0.14 mg GAE/g DW) and the total flavonoid content (5.15 ± 0.03 mg QE/g DW) were found in the water extract. The results indicated that the obtained EPS were heteropolysaccharides with glucose as the main building monosaccharide and minor amounts of mannose, xylose, galactose, fucose and glucuronic acid. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the complex structure of the crude EPS. Five probiotic lactic acid bacteria strains were used for the determinati...
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Emirates Journal of Food and Agriculture, 2020
The aim of the present study was to manufacture fresh cheese Labneh enriched with antioxidative c... more The aim of the present study was to manufacture fresh cheese Labneh enriched with antioxidative compounds from pepper (Capsicum annuum) extracts encapsulated in alginate beads. The carbohydrate content, total phenolic, and carotenoids content, as well as the antioxidant activity of prepared Labneh samples, were evaluated. The microbiological screening on the 1st and 20th day of storage period at 4 ± 1 °C was performed as well. The obtained results for chemical properties illustrated that the addition of alginate-encapsulated pepper (Capsicum annuum) extracts in Labneh had a significant effect (p<0.05) on the level of total phenols and antioxidant activity in comparison with the control sample. The presence of lactose, galactose and glucose were detected in all samples. It was established that the total viable lactic acid bacterial count (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) in the experimental samples decreased at the end of the storage period...
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Food Science and Applied Biotechnology, 2019
We report for the first time fumaric acid biosynthesis by in vitro systems of Fumaria spp. The hi... more We report for the first time fumaric acid biosynthesis by in vitro systems of Fumaria spp. The highest amount of fumaric acid (137 mg/L) was accumulated by Fumaria officinalis L. plant cell culture, cultivated at submerged conditions in darkness. The prospects for efficient process development were also discussed.
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BIO Web of Conferences, 2022
In the present work, ice cream mixtures with 5%, 10% and 15% lingonberry extract were studied. Th... more In the present work, ice cream mixtures with 5%, 10% and 15% lingonberry extract were studied. The lingonberry (Vaccinium vitis-idaea L.) is a source of anthocyanins and flavonoids, which are the bioactive components with good antioxidant properties. There was a significant increase in antioxidant activity (p<0.05) from 133.3 ± 5.6 mM TE/100 g to 249.8 ± 8.3 mM TE/100 g (ABTS method) with increasing the concentration of the extract from 5% to 15%, respectively. Significant changes (p<0.05) in the acidity and dry matter of the samples with lingonberry extract were recorded. After 30 days of storage, a decrease in the antioxidant properties (p<0.05) of the ice cream samples was observed but higher values (mM TE/100 g) were maintained compared to the sample without extract. The color characteristics of the samples were also influenced by the concentration of the extract used. During storage, the highest stability of the colorimetric index a* (red component) was established, wh...
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The aim of the present study was to investigate the antioxidant activity and the fructan content ... more The aim of the present study was to investigate the antioxidant activity and the fructan content of Bulgarian Carduus thoermeri Weinm. flower heads. The antioxidant activity of the extracts was evaluated by several reliable methods such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2′-azinobis-3 ethyl benxothiazoline-6-sulphonic acid (ABTS) cation decolorization activity assays, the ferric reducing/antioxidant power method (FRAP) and cupric ion reducing antioxidant capacity assay (CUPRAC) in addition to the total phenolic content evaluation. The reported results could be considered as first detailed investigation on the sugar and inulin content of Bulgarian C. thoermeri. The content of inulin in the plant samples was evaluated to be 0.7% dry weight (dw). In the water extracts besides the fructose, sucrose and nystose, the presence of high molecular fraction of inulin was determined. Based on the established inulin content the use of infusions and tinctures f...
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Annals of the University Dunarea de Jos of Galati. Fascicle VI: Food Technology, 2018
New approach of alginate encapsulation of polyphenolic rich extract from three wild edible forest... more New approach of alginate encapsulation of polyphenolic rich extract from three wild edible forest fruits Cornelian cherry, chokeberry and blackberry was introduced. The aim of the current study was to design new dairy desserts with antioxidant properties by encapsulation and direct incorporation of berries juices The microencapsulation of berries extracts significantly retains (p < 0.05) higher amount of polyphenols and antioxidants in dairy desserts not only at the first day, but also after twenty days storage period. The highest antioxidant activity (523 mM TE/100 g (DPPH method) and 510 mM TE/100 g (FRAP method)) demonstrated dairy dessert with encapsulated blackberry juice followed by chokeberry and Cornelian cherry alginate encapsulated juices. The sensory evaluation of obtained dairy desserts with encapsulated berries juices showed satisfactory and overall higher scores for proposed new desserts compared to the direct incorporated fruits juices. Alginatebased encapsulation ...
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The Lemon balm (Melissa officinalis L.) is an important aromatic and medicinal plant from Lamiace... more The Lemon balm (Melissa officinalis L.) is an important aromatic and medicinal plant from Lamiaceae family. Its leaves and essentials oils are used in folk medicine for the treatment of fevers and colds, hyperthyroidism, headaches and toothaches. Melissa officinalis is a rich source of volatile oil, flavonoid glycosides and derivatives of caffeic acid (rosmarinic acid). The aim of current study was to evaluate and compare the polyphenol content and antioxidant activity of infusions prepared from commercially available lemon balm brands on Bulgarian market. The total polyphenol content was established to be in range from 18.17 ± 0.04 to 64.17 ± 0.52 mg GAE/g dw, the total derivatives of caffeic acid from 3.80 ± 0.05 to 21.66 ± 0.10 mg CAE/g dw, caffeic acid content from 0.16 ± 0.01 to 0.97 ± 0.03 mg/g dw and rosmarinic acid between 2.4 ± 0.02 and 23.1 ± 0.5 mg/g dw, respectively. In vitro radical scavenging activity was evaluated by DPPH method (106.31 ± 9.87-553.51 ± 46.04 mM TE/g d...
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Biointerface Research in Applied Chemistry, 2021
The task of this study was to perform the "green" synthesis of lactose octaacetate thro... more The task of this study was to perform the "green" synthesis of lactose octaacetate through microwave irradiation and to establish their biological activities. Lactose ester was prepared after microwave-assisted esterification of lactose with acetic anhydride (yield 85-90 %). Lactose octaacetate was characterized by a high degree of acetylation (DS 3.2-3.7). The lactose esters' structure was elucidated by infrared spectroscopy and nuclear magnetic resonance spectroscopy. Lactose octaacetate showed better antifungal activities than antibacterial activities. It possessed slight to moderate antifungal activities against Aspergillus niger ATCC 1015, Penicillium sp., Rhizopus sp., Fusarium moniliforme ATCC 38932. Lactose acetates demonstrated low cytotoxicity against three cell lines: Madin-Darby bovine kidney (MDBK) cells, human epithelial type 2 (HEp-2), and Madin-Darby canine kidney (MDCK) cells. This is the first report for antiviral activity of lactose acetates against ...
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journal of applied pharmaceutical science, 2017
Abstract: European cinquefoil (Potentilla reptans L.) (Rosaceae) is very common in the Central Eu... more Abstract: European cinquefoil (Potentilla reptans L.) (Rosaceae) is very common in the Central Europe and Balkan Peninsula. Since ancient times the European cinquefoil have been traditionally used in herbal medicine for treatment of tooth ache, ulcers and inflammation of the throat, as well as certain forms of cancer, infections due to bacteria, fungi and viruses, diarrhea, diabetes mellitus and other ailments. Most species of order Potentilla contain hydrolysable tannins, proanthocyanidins, flavonoids and triterpens as bioactive substances. The aim of this study was to establish the best condition for extraction of biologically active substances from Potentilla reptans aerial part. The influence of the duration of the ultrasonic extraction and solvent system (ethanol-water) in different concentration ratio over the extraction process was studied. The optimal conditions for the extraction of biologically active substances from European cinquefoil were as follow 40% ethanol-water as ...
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Moraceae is very common in the Mediterranean region and in the countries with dry and warm climat... more Moraceae is very common in the Mediterranean region and in the countries with dry and warm climate. Since ancient times the figs have been used for human consumption, but it was only recently that their nutritive and pharmacological value has been investigated. The aim of the current study was to investigate the metabolites profile of the different extracts (diethyl ether, petroleum ether, n-hexane, acetone and ethanol) from Ficus carica leaves. The highest yield of the extractable components has been obtained with n-hexane – 5.0 g/100 g dw. Thirty-seven unpolar compounds have been identified by GC-MS analysis. In the investigated extracts were mainly detected the following phytochemical compounds: saturated and unsaturated fatty acids (18% of TIC) – myristic acid, palmitic acid, margaric acid, linoleic acid, α-linolenic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid; fatty alcohols (35% of TIC) – stearyl, behenyl, pentacosan-1-ol, ceryl, montanyl, m...
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Agricultural Science and Technology, 2017
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""Ultrasonic fractional extraction of fructooligosaccharides and inulin from Jerusalem ... more ""Ultrasonic fractional extraction of fructooligosaccharides and inulin from Jerusalem artichoke tubers has been carried out. The following conditions as the type of the used solvent- n-propanol, 95% (v/v) ethanol and distilled water and the duration of the extraction process have been varied. The contents of sugars and fructans in the obtained extracts were determinated by spectrophotometric method based on resorcinol reaction and by TLC analysis. The greatest amounts of fructooligosaccharides and inulin have been extracted by distilled water (46 g/100g d.w.), as each ultrasonic extraction was carried out in triplicate for 30 min. The best solvent used for the separation of a particular fraction fructooligosaccharides consisting of kestose, nystose and fructofuranosylnystose was n-propanol.""
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Plants, 2021
The purpose of the current study was to identify and quantify triterpenoids and other non-polar c... more The purpose of the current study was to identify and quantify triterpenoids and other non-polar compounds in the leaves of three high bush blueberry cultivars (Vaccinium corymbosum L. var. Bluegold, var. Bluecrop and var. Elliott) and three natural populations of Vaccinium species (Vaccinium uliginosum L., Vaccinium myrtillus L. and Vaccinium vitis-idaea L.) by means of gas chromatography mass spectrometry (GC-MS) and high-performance liquid chromatography with diode array detector (HPLC-DAD). Metabolite profiles differed significantly among the Vaccinium species analyzed, as well as among the populations of the same species. The populations of V. vitis-idaea predominantly contained relative concentrations of phytosterols (varying between 10.48% of total ion current (TIC) and 22.29% of TIC) and almost twice the content of triterpenes (from 29.84% of TIC to 49.62% of TIC) of the other berry species investigated. The leaves of V. corymbosum varieties biosynthesized the highest relativ...
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Acta Scientiarum Polonorum Technologia Alimentaria, 2020
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Polish Journal of Food and Nutrition Sciences, 2020
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Papers by Nadezhda Petkova