Browsing by Author "Kirova E."
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Item Comparison of citrus peels as a source of valuable components - Polyphenols and antioxidants(2013-11-05) Karsheva M.; Kirova E.; Alexandrova S.; Georgieva S.The aim of this study is to compare some citrus fruits' peels: mandarins and grapefruits, as sources of polyphenolic compounds, to determine the antioxidant activity of the extracts and to find the effect of the operational conditions on the final extract properties. It was found that the both materials are rich of polyphenols and exhibit high antioxidant activity; better results are obtained for the grapefruit peels. The flavonoids' content in both materials studied is quite close. The solid-to-liquid ratio plays an important role in the extraction process. The better results are obtained for the ratio of 1:10. The results of this study confirm that the citrus peels are promising source of natural antioxidants and polyphenols.Item Improvement of Stevia rebaudiana Bertoni In Vitro Propagation and Steviol Glycoside Content Using Aminoacid Silver Nanofibers(2022-10-01) Sichanova M.; Geneva M.; Petrova M.; Miladinova-Georgieva K.; Kirova E.; Nedev T.; Tsekova D.; Iwanov I.; Dochev K.; Ivanova V.; Trendafilova A.The food industry is interested in replacing artificial sweeteners with natural sugars that possess zero calories and carbohydrates and do not cause spikes in blood sugar levels. The steviosides leaves, synthesized at Stevia rebaudiana Bertoni, are 300 times sweeter than common table sugar. Stevia propagation is limited due to the poor viability of the seeds, the long time and low germination rate, and the poor rooting ability of vegetative cuttings. Because of this, an alternative biotechnological method for its reproduction is being studied, such as multiple shoot production through direct organogenesis using nanofibers, formed from a derivative of amino acid valine as a carrier of the biologically active agent silver atoms/particles (NF-1%Ag and NF-2%Ag). The stevia explants were cultured on a medium containing NF-1%Ag and NF-2%Ag at concentrations of 1, 10, 50, and 100 mg L−1. The NF-1%Ag and NF-2%Ag treatment caused hormetic effects on stevia plantlets. At low concentrations of from 1 to 50 mg L−1 of nanofibers, the stimulation of plant growth was observed, with the maximum effect being observed at 50 mg L−1 nanofibers. However, at the higher dose of 100 mg L−1, inhibition of the values of parameters characterizing plant growth was recorded. The presence of nanofibers in the medium stimulates stevia root formatting.Item Influence of the Abiotic Elicitors Ag Salts of Aspartic Acid Derivatives, Self-Organized in Nanofibers with Monomeric and Dimeric Molecular Structures, on the Antioxidant Activity and Stevioside Content in Micropropagated Stevia rebaudiana Bert.(2023-10-01) Sichanova M.; Geneva M.; Petrova M.; Miladinova-Georgieva K.; Kirova E.; Nedev T.; Tsekova D.; Ivanova V.; Trendafilova A.The use of nanomaterials in biotechnology for the in vitro propagation of medical plants and the accumulation of certain biologically active metabolites is becoming an efficient strategy. This study aimed to evaluate the influence of the concentration (0, 1, 10, 50, and 100 mg L−1) of two types of nanofibers on the growth characteristics, the antioxidant status, and the production of steviol glycosides in micropropagated Stevia rebaudiana Bert. plantlets. The nanofibers were synthesized by aspartic acid derivatives (L-Asp) Ag salts self-organized into nanofibers with two different molecular structures: monomeric, containing one residue of L-Asp with one hydrophilic head which bonds one Ag ion (NF1-Ag salt); and dimeric, containing two residues of L-Asp with two hydrophilic heads which bond two Ag ions (NF2-Ag salt). An increase in the shoots from the explants’ number and length, biomass accumulation, and micropropagation rate was achieved in the plants treated with the NF1-Ag salt in concentrations from 1 to 50 mg L−1 after 30 days of in vitro proliferation compared to the NF2-Ag salt. In contrast, the plants grown on MS media supplemented with NF2-Ag salt exhibited an increase in the level of stevioside, rebaudioside A, and mono- (CQA) and dicaffeoylquinic (DCQA) acids as compared to the NF1-Ag salt.Item Natural antioxidants from citrus mandarin peels. extraction of polyphenols; effect of operational conditions on total polyphenols contents and antioxidant activity(2013-05-22) Karsheva M.; Kirova E.; Alexandrova S.The main waste of the citrus fruits after processing is the citrus peel. The extraction of valuable components from mandarin peels with ethanol-in-water solutions was investigated. The effect of the operational conditions on the total extracted amount, the totalpolyphenols content and antioxidant activity was studied. The conditions varied were: theethanol concentration, the particle size and the temperature. Taking into account the thermolability of the polyphenols, vitamin C, etc., the influence of the drying temperature on the properties of extracts after re-dissolution was studied. It was found that the increase in drying temperature leads to decrease in TPPC in the extracts after re-dissolution. The worst results were obtained for drying temperature of 60°C - total polyphenols contents after drying and re-dissolution decreased almost twice (2.22 times). The comparison in TPPC and AOA of the mandarin peels' extracts with other citrus peels shows that the source studied is a perspective for possible use in food and cosmetic industries due to thevaluable components in it.Item Relative effectiveness coefficient: A quality characteristic of toothpastes containing active components(1996-01-01) Borissova R.; Kirova E.It has been proposed that the parameter of relative effectiveness coefficient (REC) be used for the qualitative assessment of toothpastes containing active ingredients. REC is the ratio between the concentration of the active component in water eluates obtained after three minutes and adequately prolonged (up to the reaching of equilibrium state) dispersion of the toothpaste in distilled water at a 1:4 ratio (condition simulating the use of toothpaste in the oral cavity). The change in REC after storage following its production, as well as testing the toothpaste stability at high and low temperatures, provides an evidence for deviations in its quality. REC was applied for the assessment of toothpastes containing 0.5% zinc citrate as an active ingredient.Item Utilization of viticulture wastes (residues) - leaves and cans(2014-01-01) Karsheva M.; Kirova E.Agricultural wastes (and especially those from viticulture) are a largely ignored source of high-value phytochemicals and high value-added industrial products. Experiments for extraction of valuable components from vineyard residues (leaves and cans) were carried out. The extraction was conducted with ethanol-in-water solutions with different concentrations (13, 20 and 40 % vol) at temperatures of 25, 40 and 60°C. It was found that the solvent concentration, as well as the temperature, influence differently both raw materials studied. The leaves have about 3 times higher TPC than the cans. The concentration of the ethanol in the extracting solution also plays an important role concerning the TPC - the best results are obtained with concentration of 40 % vol. The antioxidant capacity of the leaves' extracts is practically not influenced by the extragent concentration. For the cans' extracts the AOC is affected by the ethanol concentration - the best results obtained for 40 % ethanol-in-water solutions. For the leaves'extracts, the TPC values are highest for the lowest temperature. On the contrary, for the cans the temperature increase leads to higher values of TPC for the highest temperature of 60°C. A possible explanation of the fact observed is their different texture leading to different diffusivities. The total polyphenols content and antioxidant activity values found are quite high and characterize the vineyard wastes as a really promising source for food, pharmaceutical and cosmetic industries.