Browsing by Author "Dimcheva V."

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    Antioxidant activity and polyphenolic content of the Bulgarian wild herb cistus incanus L. stored under different conditions
    (2017-01-01) Dimcheva V.; Karsheva M.
    Present study investigates the effect of storage (at room temperature and at a frozen state) of Cistus incanus leaves and its hard-coated seeds on the total polyphenol content and the antioxidant capacity in view of the extraction carried out in 50 % ethanol-in water solution. A correlation between the polyphenol content and the antioxidant activity of the leaves stored at room temperature is elucidated. The frozen stored material generates better extraction efficiency and keeps a very high antioxidant activity. This investigation demonstrates that Cistus incanus from Strandja Mountain, Bulgaria is an important source of polyphenols and antioxidant activity. The latter is present in leaves stored for a couple of years. The results from this study contribute to better understanding the extraction process of this non- traditional Bulgarian herb.
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    Cistus incanus from strandja mountain as a source of bioactive antioxidants
    (2018-03-01) Dimcheva V.; Karsheva M.
    The purpose of the present study is to survey the extraction conditions and explore the antioxidant potential of the wild herb Cistus incanus, which is non-traditional in Bulgarian ethnomedicine and widespread in the Strandja Mountain. The influence of the extraction time (0-500 min) and solvent composition (0-50% ethanol in water) on the polyphenols, flavonoid yields and on the antioxidant capacity of the extracts of leaves, stalks (wood parts) and bud mixture were studied. The antioxidant capacity (AOC) was evaluated by use of scavenging assays of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. Total polyphenol and flavonoid contents were quantified using UV-vis (ultraviolet-visible) spectrophotometry. The optimal yield of the desired components was obtained with 30% ethanol in water solvent at the 390th min of extraction time. In addition, the influence of seasonality (winter and summer Cistus incanus), and of the different aerial parts-hard-coated seeds, buds, and a mixture of leaves and stalks of the wild plant-on the presence of polyphenols, flavonoids, and AOC were investigated. The present work revealed that the high values of polyphenols, flavonoids and the high AOC occurred not only in the summer leaves, but were also found in the winter leaves, hard-coated seeds, buds, and stalks. Based on the obtained results, the Cistus incanus from Strandja Mountain could be an excellent new source of natural antioxidants in food and for the pharmaceutical industries.
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    Optimization and comparison of different techniques for extraction of flavonoids of Bulgarian Mavrud grape by-products
    (2019-01-01) Dimcheva V.; Karsheva M.
    In recent years, the interest in antioxidants in grape by-products has increased significantly as scientific research for the extraction and quantification of these compounds. In the present investigation was optimized the antioxidant yield of the grape pomace and seeds discharged as waste from the Bulgarian Mavrud winery, near to Trakiets village. There is a lack of information about extraction optimization and utilization of the selected grape by-products. The aim of the paper was studying the influence of some process parameters: effect of the degreasing pre-treatment of the material, effect of the extraction method and the extraction time on the yield of total flavonoid and anthocyanin contents and Trolox equivalent antioxidant capacity (TEAC). For this propose the extraction kinetics were obtained by using conventional and non-conventional extraction methods-magnetic stirring and ultrasound-assisted extraction (UAE) and using of degreased and non-degreased plant material. Degreasing was done by conventional Soxhlet extraction with n-hexane for an hour. All analyses were done using ultraviolet-visible (UV-vis) spectrophotometry. The results obtained show that the applied ultrasound power after the degreasing pre-treatment promoted optimal anthocyanin and flavonoid recovery for 180 minutes extraction time of both-grape pomace and seeds. The TEAC is not affected by applying UAE and degreasing pre-treatment technique. The optimization of the extraction conditions is important because it could alter an economic impact on the extraction evaluation of the Mavrud grape by-products. The grape pomace and seeds from Bulgarian Mavrud wine-making can be used to obtain secondary derivatives with high-added antioxidant value.
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    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.