Browsing by Author "Yanev S."

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    Esterification of mixtures of pure fatty acids with methanol
    (2013-11-05) Cholakov G.; Yanev S.; Markov V.; Stoyanov S.
    Extracts from secondary biomass, e. g. spent coffee grounds (SCG), can be utilized in the production of biodiesel additives (esters of fatty acids with low molecular mass alcohols). However, they contain a significant amount of free fatty acids, so the transesterification of their glycerides has to be preceded by catalytic esterification of these acids. SCG extracts are essentially a mixture of compounds with approximately equal amounts of glycerides with saturated and unsaturated fatty acid moieties, so their iodine values are much lower than those of the typical highly unsaturated biodiesel feedstocks - e.g., sunflower oil, soybean oil, etc. In the wider context of our studies on the preparation of renewable fuel additives from SCG and other extracts from secondary biomass, this work presents results on direct esterification of mixtures of pure fatty acids, modeling the unsaturation of such extracts. They are also relevant to the utilization of biodiesel feedstocks, consisting entirely or predominantly of fatty acids like tall oil, soapstock and synthetic fatty acids, etc.
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    Extracts from coffee by-products as potential raw materials for fuel additives and carbon adsorbents
    (2013-11-05) Cholakov G.; Toteva V.; Nikolov R.; Uzunova S.; Yanev S.
    Data about coffee consumed world-wide are somewhat contradictory. A conservative estimate, suggests a number of around 8 mln tones per year. Its production involves a comparable amount of by-products, mainly pulp, husks, skins and spent coffee grounds. Thus, a sustainable coffee industry requires the development of methods for utilization of coffee by-products. Among these, the preparation of renewable fuel additives (e.g. biodiesel) and carbon adsorbents is a promising alternative to the eventual dumping of biogenic substances, harmful to the environment. Extraction of coffee by-products is the first step towards their utilization. This work presents results on laboratory extraction of spent coffee grounds (SCG) with different solvents, discussed in the context of the preparation of renewable fuel additives. The aim of the present study is to develop a procedure for extraction of coffee residues, suitable for production of biofuels and adsorbents.
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    In vitro and ex vivo studies on angiotensin-i converting enzyme (Ace) inhibitory activity of short synthetic peptides
    (2021-01-01) Yakimova B.; Mateeva P.; Kardaleva P.; Stoineva I.; Todorova P.; Zamfirova R.; Yanev S.
    In our days the interest in the studies of new angiotensin-converting-enzyme (ACE) inhibitors as modulators of the renin-angiotensin-system (RAS) is growing, not only because of their importance as drugs for arterial hypertension treatment, but also for their therapeutic potential during COVID-19 infection. This study presents data for the design and synthesis of short peptides by SPPS strategy and investigates in vitro and ex vivo their potential as ACE inhibitors in the light of structural changes. The obtained results give insight into the structure-activity relationship of peptide sequences and show differences regarding the effects of peptides in two experimental procedures (inhibitory potency on purified ACE activity and AT-I induced rat ileum contractions). Three of the newly synthesized peptides with terminal proline, LAP, LKP and VAP, showed relatively high inhibitory activities.