Spas Krumov Sotirov (1929-2016) - naturalist and biologist

In memoriam biography of dr Spas Sotirov

Rapid bone regeneration with nano-hydroxyapatite coated with a chitosan-poly (D, L)-lactide-co-glycolide bone-filling material with osteocondactive and antimicrobial properties

Composite biomaterials based on nano-hydroxyapatite have an enormous potential for natural bone tissue reparation, filling and augmentation. Multifunctional nanoparticulate systems based on HAp coated with biocompatible and bioresorbable polymers make a separate group of filler systems in bone tissue engineering [1,2]. Chitosan has many physicochemical (reactive OH and NH2 groups) and biological (biocompatible, biodegradable) properties that make it an attractive material for use in bone tissue engineering. However, chitosan may induce thrombosis and it is therefore unsuitable as blood – contacting biomaterial. One of the strategies to improve the biocompatibility of chitosan is combination of this biopolymer with compounds that exhibit complementary properties. In our studies, we present the synthesis, characterization, in vitro and in vivo research of a particulate form of nano HAp-coated polymer systems. We synthesized nanoparticulate HAp coated with chitosan (Ch) and a chitosan-poly-D,L-lactide-co-glycolide (Ch-PLGA) polymer blend obtained via the solvent/non-solvent method and freeze-drying processing. We also examined the possibility of using Thermo-Gravimetric Analysis/Differential-Thermal Analysis (DTA/TGA) coupled on-line with mass spectrometry (MS) as a finger print for identification purposes in coating processes. The quantitative antimicrobial test has shown that HAp/Ch-PLGA have some antibacterial properties (MIC (mg/mL): Pseudomonas aeruginosa – 6.40, Staphylococcus aureus – 6.40, Staphylococcus epidermidis – 3.20). MTT assay was used to test cytotoxicity and cell viability. By using HAp/Ch-PLGA in the form of a filler a high level of reparatory ability, with the presence Haversian canals and cement lines in reconstructed of bone defect, was achieved in vivo. [1] N. Ignjatovic, C. Liu, J. Czernuszka, D. Uskokovic, Micro and nano/injectable composite biomaterials containing calcium phosphate coated with poly(dl-lactide-co-glycolide), Acta Biomaterialia, 3 (2007) 927-935 [2] N. Ignjatović, V. Uskoković, Z. Ajduković, D. Uskoković, Multifunctional hydroxyapatite and poly(D,L-lactide-co-glycolide) nanoparticles for the local delivery of cholecalciferol, Materials Science and Engineering: C 33 (2013) 943–95

Antimicrobial activity of Satureja hortensis L. essential oil against pathogenic microbial strains

A hydro-distilled oil of Satureja hortensis L. was investigated for its antimicrobial activity against a panel of 11 bacterial and three fungal strains. The antimicrobial activity was determined using the disk-diffusion and broth microdilution methods. The essential oil of S. hortensis L. showed significant activity against a wide spectrum of Gram (-) bacteria (MIC/MBC=0.025-0.78/0.05-0.78 μl/ml) and Gram (+) bacteria (MIC/MBC=0.05-0.39/0.05-0.78 μl/ml), as well as against fungal strains (MIC/MBC=0.20/0.78 μl/ml). The results indicate that this oil can be used in food conservation, treatment of different diseases of humans, and also for the treatment of plants infected by phytopathogens

Antimicrobial Effectiveness of Selected Vranac Wines Against Six Gram-Positive and Six Gram-Negative Bacterial Strains

Purpose: The aim of this study was to assess potential antimicrobial effectiveness of selected red wines from Balkan region, made from autochthonic Vranac V. vinifera L. grape variety. Methods: The antimicrobial activity of Vranac wines against Gram-positive: C. perfringens, B. subtillis, S. aureus, L. inocua, S. Lutea, and M. flavus and Gram-negative: E. coli, P. aeruginosa, S. enteritidis, S. sonnei, K. pneumonia and P. vulgaris bacteria stains were studied using the agar well diffusion and micro-well dilution methods. The concentrations of the wine phenolic compounds: gallic acid, caffeic acid, (+)-catechin, resveratrol, quercetin, quercetin-3-glucoside and malvidin-3-glucoside were determined using HPLC analysis. Results: There was excellent correlation between the contents of gallic acid, caffeic acid, resveratrol, quercetin, quercetin-3-glucoside and malvidine-3-glucoside and the antimicrobial activity of the wines against Gram-positive - C. perfringens and M. flavus (from 0.936 to 0.999) and against Gram-negative bacteria stains - E. coli, P. aeruginosa, S. enteritidis, S. sonnei and P. vulgaris (from 0.904 to 0.999). Furthermore, the content of (+)-catechin has good correlation with the antimicrobial activity of the wines only against L. inocua and P. vulgaris with correlation coefficient of 0.996 and 0.999, respectively. All selected wine phenolic compounds, however, did not show correlation with antimicrobial activity against K. pneumonia strain. Conclusion: The antimicrobial activity of selected Vranac wines indicates that some of the wine's phenolic constituents have the potential to inhibit the growth of certain bacterial strains

Chitosan-PLGA polymer blends as coatings for hydroxyapatite nanoparticles and their effect on antimicrobial properties, osteoconductivity and regeneration of osseous tissues

Composite biomaterials comprising nanostructured hydroxyapatite (HAp) have an enormous potential for natural bone tissue reparation, filling and augmentation. Chitosan (Ch) as a naturally derived polymer has many physicochemical and biological properties that make it an attractive material for use in bone tissue engineering. On the other hand, poly-D,L-lactide-co-glycolide (PLGA) is a synthetic polymer with a long history of use in sustained drug delivery and tissue engineering. However, while chitosan can disrupt the cell membrane integrity and may induce blood thrombosis, PLGA releases acidic byproducts that may cause tissue inflammation and interfere with the healing process. One of the strategies to improve the biocompatibility of Ch and PLGA is to combine them with compounds that exhibit complementary properties. In this study we present the synthesis and characterization, as well as in vitro and in vivo analyses of a nanoparticulate form of HAp coated with two different polymeric systems: (a) Ch and (b) a Ch-PLGA polymer blend. Solvent/non-solvent precipitation and freeze-drying were used for synthesis and processing, respectively, whereas thermogravimetry coupled with mass spectrometry was used for phase identification purposes in the coating process. HAp/Ch composite particles exhibited the highest antimicrobial activity against all four microbial strains tested in this work, but after the reconstruction of the bone defect they also caused inflammatory reactions in the newly formed tissue where the defect had lain. Coating HAp with a polymeric blend composed of Ch and PLGA led to a decrease in the reactivity and antimicrobial activity of the composite particles, but also to an increase in the quality of the newly formed bone tissue in the reconstructed defect area.This is the peer-reviewed version of the articleIgnjatović, N., Wu, V., Ajduković, Z., Mihajilov-Krstev, T., Uskoković, V., Uskoković, D., 2016. Chitosan-PLGA polymer blends as coatings for hydroxyapatite nanoparticles and their effect on antimicrobial properties, osteoconductivity and regeneration of osseous tissues. Materials Science and Engineering: C 60, 357–364. [https://doi.org/10.1016/j.msec.2015.11.061]Published version: [https://vinar.vin.bg.ac.rs/handle/123456789/7570

Phytochemistry, Toxicology and Therapeutic Value of Petasites hybridus Subsp. Ochroleucus (Common Butterbur) from the Balkans

Petasites hybridus (Common butterbur) is extensively used in traditional medicine, and is currently gaining interest and popularity as a food supplement and for its medicinal properties. It contains a large number of active compounds of potential therapeutic activity, but also toxic pyrrolizidine alkaloids. Science-based information is needed to support the developing modern use of this plant, and to direct continued safe practice in traditional medicine. The present study focused on the essential oils from leaves and rhizomes of the understudied P. hybridus ssp. ochroleucus from the Balkans, and evaluated its phytochemistry and potential therapeutic activities (antimicrobial, antioxidant, anti-cholinesterase and anti-inflammatory), as well its toxicology potential (acute toxicity in insects and mice). We studied the essential oils, which are not commonly used in traditional practices, but have a potential for safe use since the toxic pyrrolizidine alkaloids, which are non-volatiles, are usually not present in the distilled essential oils. Pyrrolizidine alkaloids were indeed not detected in the essential oils; ingestion of the essential oils did not induce toxicity signs in mice, and topical application did not elicit skin irritation in humans. The essential oils had no antimicrobial properties against 20 pathogenic bacterial strains, but demonstrated good local anti-inflammatory activity in a Carrageenan-induced paw edema test. An insect toxicity test demonstrated that the leaf essential oil is an efficient insect repellent, and the demonstrated anti-cholinesterase activity suggests a potential for the treatment of neurological conditions. Isopetasin, a sesquiterpene found in plants of the genus Petasites, known to have anti-inflammatory effects, was present only in the rhizomes essential oil (3.9%), and sesquiterpene lactones concentrations were high, likely contributing to the antioxidant activity

ANTIOXIDANT AND ANTIMICROBIAL POTENTIAL OF OPOPANAX HISPIDUS(APIACEAE) EXTRACTS

The present study was aimed to investigate antioxidant and antimicrobial potential of methanol and ethyl-acetate extracts from dried aerial parts, inflorescences and fruits of Opopanax hispidus (Friv.) Griseb., fam. Apiaceae. The antioxidant potential was evaluated with the help of two in vitro antioxidant models – DPPH and ABTS assays and estimation of total phenolic and flavonoids using spectrophotometric methods. BHA and Vitamin C were used as standard and positive control for above models. Microdilution assay was used to evaluate antimicrobial potential for the most common human gastrointestinal pathogenic microbial strains. The results of DPPH and ABTS assay showed that the highest antioxidant activity have methanol (IC50=1.157 mg/ml) and ethyl-acetate (IC50=3.167 mg/ml) extracts from inflorescences. The highest value of total phenolic (89.95±0.005 mg GA/g) and total flavonoid (24.06 ± 0.004 mg Qu/g) was measured in inflorescences extracts also. Results indicate that both extracts (methanol and ethyl-acetate) of inflorescences have high amount of phenol and flavonoids, which could be responsible for its good antioxidant activity.The most susceptible were Listeria monocytogenes and Escherichia coli on ethyl-acetate extracts from fruits and inflorescence, respectively. This is the first record of antioxidant and antimicrobial activity of Opopanax hispidus from Serbia. It is also worth noting that these results validate the therapeutic use of the plant in traditional medicine

Phytochemistry, Toxicology and Therapeutic Value of Petasites hybridus Subsp. Ochroleucus (Common Butterbur) from the Balkans

Petasites hybridus (Common butterbur) is extensively used in traditional medicine, and is currently gaining interest and popularity as a food supplement and for its medicinal properties. It contains a large number of active compounds of potential therapeutic activity, but also toxic pyrrolizidine alkaloids. Science-based information is needed to support the developing modern use of this plant, and to direct continued safe practice in traditional medicine. The present study focused on the essential oils from leaves and rhizomes of the understudied P. hybridus ssp. ochroleucus from the Balkans, and evaluated its phytochemistry and potential therapeutic activities (antimicrobial, antioxidant, anti-cholinesterase and anti-inflammatory), as well its toxicology potential (acute toxicity in insects and mice). We studied the essential oils, which are not commonly used in traditional practices, but have a potential for safe use since the toxic pyrrolizidine alkaloids, which are non-volatiles, are usually not present in the distilled essential oils. Pyrrolizidine alkaloids were indeed not detected in the essential oils; ingestion of the essential oils did not induce toxicity signs in mice, and topical application did not elicit skin irritation in humans. The essential oils had no antimicrobial properties against 20 pathogenic bacterial strains, but demonstrated good local anti-inflammatory activity in a Carrageenan-induced paw edema test. An insect toxicity test demonstrated that the leaf essential oil is an efficient insect repellent, and the demonstrated anti-cholinesterase activity suggests a potential for the treatment of neurological conditions. Isopetasin, a sesquiterpene found in plants of the genus Petasites, known to have anti-inflammatory effects, was present only in the rhizomes essential oil (3.9%), and sesquiterpene lactones concentrations were high, likely contributing to the antioxidant activity

TOTAL PHENOLIC AND FLAVONOID CONTENTS, ANTIOXIDANT AND ANTIBACTERIAL ACTIVITIES OF SELECTED HONEYS AGAINST HUMAN PATHOGENIC BACTERIA

The study analyzed colour intensity, the total phenolic and flavonoid contents, as well as antioxidant and antibacterial activities of honeys from Serbia. All the tested honeys contained considerable levels of phenolics. The highest phenolic content was obtained in forest honey - 1389.71 mg gallic acid equivalents/kg. High levels of phenolics and flavonoids were also determined in honeydew, meadow and oregano honeys. The radical scavenging activity measured by DPPH method in linden and forest honey was 0.45 and 2.75 mmol Trolox equivalents/kg, respectively. The ferric reducing potential was the greatest in forest honey - 6.04 mmol Fe2+/kg. Darker honeys had a greater phenolic content and antioxidant activity. The antimicrobial activity of honeys against six bacterial strains isolated from human material were studied using a microwell dilution assay. The minimal inhibitory concentration of honeys ranged from 6.25% w/w (for oregano honey against Enterococcus faecalis and honeydew honey against Streptococcus pneumoniae) to >50% w/w (meadow honey against Staphylococcus aureus). The minimal bactericidal concentration ranged from 12.5% w/w (honeydew and bee pollen enriched honey against E. faecalis) to >50% w/w. Higher values of antimicrobial activities were found in honeydew, oregano, and forest honeys, while meadow honey showed the lowest antimicrobial activity. Analyzed honeys exhibited a strong antioxidant and broad-spectrum antibacterial activity against multidrug-resistant pathogenic bacteria. Phenolic compounds, especially in dark amber forest and honeydew honey, as well as in amber oregano honey, may contribute to their efficacy in therapeutic administration