Browsing by Author "Diankov S."
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Item COMPARATIVE STUDY OF POLYPHENOLIC COMPOSITION AND REDUCING PROPERTIES OF EXTRACTS OF CANNABIS SATIVA L., CANNABIS INDICA AND CANNABIS HYBRID(2024-01-01) Vetskov N.; Kaloyanov N.; Hinkov I.; Diankov S.; Pashova K.; Gerasimova V.; Funeva-Peycheva M.; Yankovska-Stefanova T.; Garbev A.Cannabis Sativa L., Cannabis Indica and Cannabis Hybrid are widespread plant species that find legal use in many countries around the world. The first of them has found considerable application in medicine, cosmetics, building construction, textile and food industries. Cannabis Indica and Cannabis Hybrid are used as raw materials for the extraction of oils that are used as pain relievers as well as for recreation purposes. The aim of the present study is to compare the polyphenolic composition of extracts from the three types of plants, by the maceration method of dry green leaf mass consisting of inflorescences and leaves. Ethanol (99.9 %) is used as an extractant, and the duration of the maceration process is seven days, at room temperature and stirring. The polyphenol composition is determined using HPLC-DAD method. The following polyphenol composition is found in extracts of Cannabis Sativa L.: epigallocatechin, rutin, myricetin, quercetin and kaempferol. On the other hand, quercetin and kaempferol are detected in the Cannabis Indica samples, while epigallocatechin, quercetin and kaempferol are present in the hybrid sort. In addition, green synthesis of silver nanoparticles by using sunlight or microwave irradiation was carried out to evaluate the reduction properties of three cannabis extracts. The least quantity of silver nanoparticles was obtained in the presence of Cannabis Sativa L. extracts. From the other two species of cannabis, microwave irradiation produces more silver nanoparticles, with smaller sizes, while exposure to direct sunlight produces fewer particles, but with larger sizes.Item Conventional Ultrasound And Microwave-Assisted Extraction Of Phenolic Compounds From Mavrud Grape, Pomace And Seeds(2020-01-01) Chimshirova R.; Karsheva M.; Diankov S.; Hinkov I.This research is dedicated to the valorization of wine industry residual products as a source of valuable compounds of interest to the food, pharmaceutical and cosmetic industries. Whole grape seeds and grape pomace of organic Mavrud of Bulgarian origin, harvested in 2016 were used. The aqueous ethanolic extracts were prepared by three different techniques: conventional extraction via magnetic stirring, ultrasound-assisted extraction (US) and microwave-assisted extraction (MW). Microwaves seemed to be more efficient in extracting the desired substances through the hard shell of the seeds. The polyphenolic content of the seed extracts, expressed as GAE (gallic acid equivalent) was remarkably higher: 58.57 mg GAE g-1 dw (first stage of MW-assisted extraction) compared to the conventional extraction with a magnetic stirrer – 7.03 mg GAE g-1 dw. The results obtained for the US extraction were similar - 49.73 mg GAE g-1 dw, but the processing time in the microwave field was considerably shorter. The US-assisted extraction was not so convenient for the grape pomace extracts - 20.47 mg GAE g-1 dw were obtained for 240 min, compared to 75.02 mg GAE g-1 dw for 20 min in the microwave field. Three analyzes were performed to determine the total polyphenolic content, antioxidant activity and anthocyanin content. The MW-assisted extraction was the most suitable for leaching of polyphenolic compounds and the extracts exhibited a higher antioxidant activity. Contrarily it has been observed that the anthocyanin content of the extracts produced via MW-assisted extraction was lower compared to the conventional and US-assisted techniques. Both techniques revealed time and energy-saving and are considered as eco-procedures.Item EPR SPECTROSCOPY INVESTIGATION ON THE ANTIOXIDANT EFFICACY OF SAMBUCUS NIGRA L (DRY FLOWERS/BLOSSOM) EXTRACT(2023-01-01) Petkova-Parlapanska K.; Diankov S.; Karsheva M.The present study aims to evaluate the antioxidant efficacy and the lipid peroxidation degree of Sambucus nigra L. (S. nigra) blossom extract after induction of biotic stress. Dry stained extracts of S. nigra flowers were analyzed by direct and indirect in vitro EPR spectroscopy. The antioxidant activity of the extract was assessed by DPPH analysis, and the inhibition of lipid peroxidation - by PBN-spin adduction, after UV-B and thermal stress. The direct EPR stable radical structures presence was established either in non-irradiated and UV-B irradiated samples. Furthermore, as before and after UV-B and thermal biotic stress, S. nigra showed well-expressed scavenging abilities and protective properties against reactive oxygen and nitrogen species such as superoxide radicals (•O2̅ ), hydroxyl radicals (•OH), and reduced lipid peroxidationItem Extraction from elderberry flowers. Examination of antioxidant capacity and total phenolic content of the extracts(2013-11-05) Diankov S.; Parlapanska K.In this work we present a study on the extraction from dry elderberry flowers at ambient temperature.50 vol. % ethanol-in-water solution as a solvent is used. The variation of total dry content in the extracts, their total polyphenol content as well as their antioxidant capacity is measured in time. The experimental data show that the plateau is reached after the 90th min. The maximum yield from 2 g dry flowers is 0.52 g (120 min), the maximum total polyphenol content is 2.312 g GA/L (120 min). The best antioxidant capacity (IC50%=6.58) is measured for the 90th min extract. Nevertheless the difference between the values obtained at 90th and at 120th min is in the order of the experimental incertitude.Item Extraction of valuable compounds from Bulgarian St. John'S Wort (Hypericum Perforatum L.). Antioxidant capacity and total polyphenolic content(2019-01-01) Chimshirova R.; Karsheva M.; Diankov S.; Hinkov I.Ethnobotanical reports claim that St. John's Wort has important biological and chemical properties and can be used for the treatment of many diseases. Most studies related to Hypericum perforatum are focused on its antidepressant effects, but it has also been examined for wound healing, antiviral and antimicrobial activity. In this study the experiments are carried out at ambient temperature at constant stirring rate. The solvent is a 50 vol. % water-ethanolic solution, the solid-to-liquid ratio is 1:10 g mL-1, and the average particle size is 0,75 mm. The results show that the antioxidant capacity and the total polyphenolic content are superior compared to those reported by other authors. The liquid extracts have been stored in a refrigerator for 9 months, then they have been examined again and it has been noticed that their antioxidant effect and total polyphenolic content are preserved. After drying at 50°C, storage and regeneration, the quality of the extracts did not change, which is important issue for long term transportation and storage.Item Optimization of extraction of antioxidants from Bulgarian Mavrud by-Products(2018-01-01) Dimcheva V.; Karsheva M.; Diankov S.; Hinkov I.Grape pomace, an abundant by-product from the wine industry, is released in large quantities but remains unused. This investigation is focused on the optimization of extraction from grape pomace and grape seeds discharged as wastes from the Bulgarian Mavrud winery. The optimized parameters refer to the solid to the solvent ratio effect (1/10 g mL-1, 1/20 g mL-1, 1/30 g mL-1, 1/40 g mL-1, 1/50 g mL-1) and the solvent concentration (water or aqueous ethanol solutions) in relation on the total polyphenol, flavonoid and anthocyanin contents. The Trolox equivalent antioxidant capacity is also determined. All analyses are performed spectrophotometrically. All extraction runs are carried out at constant extractive parameters chosen previously - temperature, sample particle size, extraction manner. The optimal conditions are selected for the Mavrud seeds and pomace - 50 % ethanol in water solution, 1:20 g ml-1 solid to solvent ratio. The selection of the best extraction conditions is of great importance because it could alter the characteristics of the final extract having an economic impact on the extraction evaluation of the Bulgarian bio-Mavrud by-products.Item Plant mediated synthesis of silver nanoparticles using extracts from Tilia cordata, Matricaria chamomilla, Calendula officinalis and Lavandula angustifolia flowers(2018-01-01) Mladenova B.; Diankov S.; Karsheva M.; Stankov S.; Hinkov I.In this work, a simple, rapid and efficient green method for silver nanoparticles synthesis was developed by using extracts from four medicinal plants: flowers of Tilia cordata, Matricaria chamomilla, Calendula officinalis and Lavandula angustifolia, acting as reducing and capping agents. Silver nitrate was used as a precursor. The effect of the sunlight exposure and/or the sonication treatment on the synthesis process was investigated. The ultraviolet-visible spectroscopy (UV-Vis) studies showed surface Plasmon resonance peaks between 432 nm and 448 nm, characteristic of spherical silver nanoparticles. The morphology of the nanoparticles produced was investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The proposed method could be easily implemented for any kind of scientific or industrial application due to its cost effective nature.Item Rheological properties of cosmetic compositions containing rosemary and grapefruit pulp and seeds extracts(2014-01-01) Petkova-Parlapanska K.; Nancheva V.; Diankov S.; Hinkov I.; Karsheva M.Modern cosmetic formulations represent a combination of synthetic and natural ingredients. Knowledge of the rheological behavior allows managing the structure and the quality of the products by means of supplement addition, regime change or mechanical and technological processing adjustment. The extraction from rosemary and grapefruit pulp and seeds with ethanol-in-water solutions is carried out in a thermostated shaker at 20°C. The total polyphenol content (TPC) and the antioxidant capacity (AOC) of the extracts are determined. The cosmetic compositions prepared are based on stearic acid, with 3-ethanolamine as emulsifier. Extracts are used as a preservative, instead of controversial lately methyl-parabens. The rheological behavior of the cosmetic formulations is studied. It is found that all compositions exhibited thixotropic flow behavior. The cosmetic emulsion containing an alcoholic extract of grapefruit seeds has different rheological behavior which may be described by the Bingham rheological model. This effect can be explained by the composition of the extract and its influence on the pH. It is found that the extract from grapefruit seeds has acidic properties and affects the pH of the medium. The cosmetic formulation with rosemary extract exhibits power low and thixotropic behavior. The purity of the cosmetic formulations was tested against E. Coli bacteria. It is found that no bacterial colonies are observed neither after one day, nor after three months of storage. It can be concluded that the natural extracts from rosemary and grapefruit seeds and pulp exhibit good antibacterial properties, being quite satisfactory substitute of the parabens.Item SILVER NANOPARTICLES INCORPORATED INTO POROUS COLLAGEN SCAFFOLDS(2022-01-01) Samichkov V.; Mladenova B.; Diankov S.; Foteva T.; Hinkov I.In this work, we present a simple, rapid and cost-effective microwave-assisted method for silver nanoparticles synthesis by chemical reduction using an aqueous solution of silver nitrate, ethanol and ammonia. The effect of reagent concentrations and the heating time was investigated. Samples were analyzed through UV-Vis spectroscopy and transmission electron microscopy. Furthermore, the obtained silver nanoparticles were mixed with collagen dispersions to prepare porous scaffolds by vacuum-sublimation drying. Silver nanoparticles can adhere to the bacterial cell wall subsequently causing its death. The microbiological study showed that the collagen scaffolds with incorporated silver nanoparticles exhibited antibacterial activity against Bacillus subtilis NBIMCC 3562 and Escherichia coli NBIMCC 407 bacteria and could find potential applications in medicine.Item THE GAMMA IRRADIATION EFFECT ON THE ANTIOXIDANT AND LIPID OXIDATION ACTIVITY OF ALMOND (PRUNUS DULCIS L.) OIL(2023-01-01) Karamalakova Y.; Slavova-Kazakova A.; Momchilova S.; Karsheva M.; Diankov S.; Nikolova G.Almond nuts (Prunus dulcis, Amygdalus subgenus inside the Prunus genus, Rosaceae family) are cultivated globally and 30 % of their worldwide production is derived from the Mediterranean region. The almond nut’s main components, like lipids (oleic, linoleic, palmitic, palmitoleic, and stearic acid), proteins, soluble sugars, minerals, fibrous, and phytochemicals, are responsible for ROS/RNS detection. In recent years, food irradiation has been used to protect against microorganisms, oxidative processes, and radiation-induced toxicity, and this methodology is internationally recognized for effective long-term storage. The ROS/RNS detection by Electron paramagnetic resonance spin - trapping provides useful information on the susceptibility to oxidative stability of gamma (γ) - irradiated food/oils for comparative purposes. In the current study by using two different methods in vitro were evaluate and compared radical-scavenging abilities and lipid oxidative stability of almond oil, at 0 kGy, 10 kGy, 25 kGy radiation, re-oxidized at 50°C. It was found that a 10 kGy irradiation dose increased membrane protection activity in the lipid phase. 10 kGy irradiated almond oil showed high reproducibility, on the 1 min - 60 min (57.3 μmol kg-1 oil), while 25 kGy irradiated extracts showed a slight decrease. Based on the EPR signals, 10 kGy irradiated almond oil show almost commensurate singlet line intensity, but with a slight change in the g value (g = 2.0054; o -semiquinone radical originates from the polyphenol substances), as opposed to 25 kGy doses decreased signal intensity and change the g = 2.0050, compared to non-irradiated oilItem Ultrasound-assisted green synthesis of silver nanoparticles and their incorporation in antibacterial cellulose packaging(2015-04-01) Popov V.; Hinkov I.; Diankov S.; Karsheva M.; Handzhiyski Y.The antimicrobial activity of nanoparticles (NPs) depends of the surface area in contact with microorganisms. The large surface area of the nanoparticles enhances their interaction with the microbes. In this work, a green, simple, rapid, and efficient ultrasound-assisted reduction method for silver nanoparticles (AgNP) synthesis is presented. For the synthesis, an aqueous solution of silver nitrate, ethanol, and ammonia was used. The adopted method can be easily implemented for any kind of scientific or industrial application due to its cost-effective nature. The effect of sonication time on the nanoparticle formation was investigated. Silver nanoparticles were analyzed through transmission electron microscopy and UV-vis spectroscopy. Antimicrobial additives can be incorporated in mass in different matrixes (polymeric or cellulosic), which is a convenient methodology to achieve antimicrobial activity. In this work, silver nanoparticles were incorporated in cellulose using an ultrasonic bath technique. The most important aspect of cellulose containing silver nanoparticles prepared by this method is its high antimicrobial efficiency. The microbiological study was carried out by a standard agar technique. The analysis showed that cellulose with incorporated silver nanoparticles exhibited strong antimicrobial activity against Escherichia coli bacteria. This makes it a promising antibacterial material for food packaging.