Browsing by Author "Trayanov I."

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    Nanofiltration process monitoring and antioxidant activity analysis of skimmed milk samples
    (2022-01-01) Trayanov I.
    Dead-end stirred cell experiments were performed with reconstituted skimmed milk and model solutions of single components (lactic acid). When a low solids concentration is presented with the feed, dead-end filtration with a selected polymeric membrane with cut-off 300 Da is a viable option to assure a high rejection of the dissolved organic compounds (> 90%), combined with a good transport at moderate pressures (20 bar, selected from prior nano-milkfiltrations) with an average flux (JP) increasing from 48 L.m−2.h−1 at 20°C and over 67 L.m−2.h−1 at 50°C until reaching a volume reduction of 5 . The DPPH antioxidant activity was effectively improved (~3 fold) with some insignificant loss due to fouling. Despite the high rejection, transmission of low-molecular weight components is detectable in the permeates, additionally the latter have astoundingly an antioxidant capacity, so each permeate can be divided into time interval fractions-aliquots each showing different DPPH antioxidant activity. This is further confirmed with statistical analysis where р < 0.05. As conclusion, because temperatures up to 50°C significantly increase the flux without much effect on the antioxidant activity, such conditions (temperature, pressure, dilution) are viable options for large-scale production applications.
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    Outstanding Antibacterial Activity of Hypericum rochelii—Comparison of the Antimicrobial Effects of Extracts and Fractions from Four Hypericum Species Growing in Bulgaria with a Focus on Prenylated Phloroglucinols
    (2023-02-01) Ilieva Y.; Marinov T.; Trayanov I.; Kaleva M.; Zaharieva M.M.; Yocheva L.; Kokanova-Nedialkova Z.; Najdenski H.; Nedialkov P.
    Microbial infections are by no means a health problem from a past era due to the increasing antimicrobial resistance of infectious strains. Medicine is in constant need of new drugs and, recently, plant products have had a deserved renaissance and garnered scientific recognition. The aim of this work was to assess the antimicrobial activity of ten active ingredients from four Hypericum species growing in Bulgaria, as well as to obtain preliminary data on the phytochemical composition of the most promising samples. Extracts and fractions from H. rochelii Griseb. ex Schenk, H. hirsutum L., H. barbatum Jacq. and H. rumeliacum Boiss. obtained with conventional or supercritical CO2 extraction were tested on a panel of pathogenic microorganisms using broth microdilution, agar plates, dehydrogenase activity and biofilm assays. The panel of samples showed from weak to extraordinary antibacterial effects. Three of them (from H. rochelii and H. hirsutum) had minimum inhibitory concentrations as low as 0.625–78 mg/L and minimum bactericidal concentrations of 19.5–625 mg/L against Staphylococcus aureus and other Gram-positive bacteria. These values placed these samples among the best antibacterial extracts from the Hypericum genus. Some of the agents also demonstrated very high antibiofilm activity against methicillin-resistant S. aureus. Ultra-high-performance liquid chromatography–high-resolution mass spectrometry revealed the three most potent samples as rich sources of biologically active phloroglucinols. They were shown to be good drug or nutraceutical candidates, presumably without some of the side effects of conventional antibiotics.