Anti-inflammatory drugs are used to relieve pain, fever, and inflammation while protecting the cardiovascular system. However, the side effects of currently available medications have limited their usage. Due to these adverse effects, there is a significant need for new drugs. The current trend of research has shifted towards the synthesis of novel anthranilic acid hybrids as anti-inflammatory agents. Phenyl- or benzyl-substituted hybrids exerted very good anti-inflammatory effects in preventing albumin denaturation. To confirm their anti-inflammatory effects, additional ex vivo tests were conducted. These immunohistochemical studies explicated the same compounds with better anti-inflammatory potential. To determine the binding affinity and interaction mode, as well as to explain the anti-inflammatory activities, the molecular docking simulation of the compounds was investigated against human serum albumin. The biological evaluation of the compounds was completed, assessing their antimicrobial activity and spasmolytic effect. Based on the experimental data, we can conclude that a collection of novel hybrids was successfully synthesized, and they can be considered anti-inflammatory drug candidates—alternatives to current therapeutics.

Members of the bacterial genus Bacillus are known as producers of a broad spectrum of antibiotic compounds of proteinaceous nature that possess inhibitory activity against different saprophytic and pathogenic microorganisms. In the current research, a peptide synthesized by Bacillus methylotrophicus strain BM47, previously isolated from a natural thermal spring in Bulgaria, was identified and characterized as a bacteriocin. In vitro antimicrobial screening of the crude bacteriocin substance of B. methylotrophicus BM47 showed activity against the plant pathogenic fungi Fusarium moniliforme, Aspergillus awamori, Penicillium sp., Aspergillus niger and Gram-negative bacterium Pseudomonas aeruginosa. The antimicrobial activity of the crude bacteriocin substance was partially inhibited by the enzymes trypsin, Alcalase®, Savinase®, proteinase K, papain and Esperase®, while catalase was not effective. The crude bacteriocin substance was relatively pH resistant, but sensitive to the action of heat and most organic solvents and detergents tested. To obtain the active protein fractions, crude bacteriocin substance was purified by fast protein liquid chromatography (FPLC) using a strong anion exchange column. Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis demonstrated that the purified bacteriocin had molecular mass of 19 578 Da. The amino acid analysis performed by high-performance liquid chromatography (HPLC) revealed that the isolated bacteriocin consisted of 17 types of amino acids, with the highest mol fraction expressed as percent of serine (29.3), valine (10.3), alanine (9.8) and tyrosine (7.1).

Propolis (bee glue) is a complex biological product known for its antimicrobial activity and antioxidant potential, and widely used as food additive and biopreservative. The aim of the present research was to examine the effects of propolis on the improvement of the storage life of ripened kashkaval cheese. For this purpose, three types of 1% carboxymethyl cellulose edible films containing three different ethanolic propolis extracts in concentration of 1% were prepared. Double-layer edible films were applied on the kashkaval cheese surface, and the samples were designated as T1, T2, and T3. An untreated sample was kept as a control. The four experimental groups (T1, T2, T3, and control) were then stored under refrigeration conditions at 4°C and 75% relative humidity (RH) for 56 days. During the storage period, the cheese was observed for visible changes, and samples for physicochemical and microbiological analyses were taken. The results from physicochemical analysis demonstrated that values of titratable acidity decreased in all experiment groups during the storage period. The results from microbiological analysis revealed that three types of edible films T1, T2, and T3 did not affect the decreasing number of lactic acid bacteria, a normal process for the period after the cheese ripening. The application of T1, T2, and T3 edible films did not affect the increasing number of yeasts in kashkaval cheese through the storage period. However, T1 and T2 edible films effectively inhibited the fungal growth on cheese surface, and no signs of spoilage were observed until the end of the storage for 56 days. In contrast, T3 treatment delayed but did not inhibit the fungal growth, and the first signs of fungal decay appeared between the 35th and 42nd day of the storage, compared to the control (28th day). Thus, the application of propolis can be considered an effective means for the prevention of fungal spoilage of kashkaval cheese.

The present study examined the physicochemical, antioxidant, and antimicrobial properties of three medicinal plants: thyme (Thymus callieri Borbás ex Velen), cotton thistle (Onopordum acanthium L.), and hawthorn fruit (Crataegus monogyna Jacq.) from the Western Rhodope Mountains, Bulgaria. The first stage determined the physicochemical characteristics (moisture, ash, carbohydrates, proteins, and vitamin C) of the three herbs. The second stage investigated four types of extracts (aqueous, oil, methanolic, and ethanolic) of each herb and evaluated their total phenolic content, the presence of phenolic compounds (flavonoids and phenolic acids), their antioxidant activity, and antimicrobial properties. Thyme was characterised by the highest ash, protein, and vitamin C content (6.62%, 11.30%, and 571 mg/100 g, respectively). Hawthorn fruit showed the highest moisture and carbohydrate content (8.50% and 4.20%, respectively). The 70% ethanolic extracts of the three herbs exhibited the highest levels of phenolic compounds and, consequently, pronounced antioxidant activity, compared to the other three types of extracts. The aqueous, oil, methanolic, and ethanolic thyme extracts demonstrated the highest total phenolic content—TPC (27.20 mg GAE/g, 8.20 mg GAE/g, 31.70 mg GAE/g, and 310.00 mg GAE/g, respectively), compared to the extracts of the other two plants. These results were consistent with the highest antioxidant activity of the thyme extracts determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, the oxygen radical absorbance capacity (ORAC) assay, and the hydroxyl radical averting capacity (HORAC) assay (except for the oil extract examined using the DPPH method). The results from the high-performance liquid chromatography (HPLC) analysis revealed that the flavonoid quercetin-3-ß-glucoside had the highest concentration in thyme (374.5 mg/100 g), while myricetin dominated in the cotton thistle (152.3 mg/100 g). The phenolic acid content analysis showed prevalence of rosmaric acid in the thyme (995 mg/100 g), whereas chlorogenic acid was detected in the highest concentration in the cotton thistle and hawthorn fruit (324 mg/100 g and 27.7 mg/100 g, respectively). The aqueous, methanolic, and ethanolic extracts showed moderate to high antibacterial potential but limited antifungal activity. None of the oil extracts inhibited the test microorganisms used in the study.

Propolis (bee glue), a valuable biological mixture produced by European honey bees (Apis mellifera L.), is widely used as a remedy in traditional and alternative medicine, as an effective food biopreservative and as a nutritional value enhancer. The present study aimed to investigate eighty propolis samples collected from all twenty-eight districts of Bulgaria in the period of 2020–2022 in order to determine their physicochemical properties as well as their antioxidant and antimicrobial potential. The raw propolis samples exhibited brown or green colour depending on the climatic zone from which they are collected and pH values from 4.82 to 5.87, while the moisture content ranged between 0.98% and 2.97%. The total phenolics content (TPC) and total flavonoids content (TFC) varied from 63.14 mg GAE/g to 737.27 mg GAE/g, and from 29.22 mg QE/g to 234.17 mg QE/g, respectively. The propolis samples demonstrated significant antioxidant potential determined by DPPH and FRAP methods, from 18.56 mM TE/g to 1598.66 mM TE/g and from 82.28 mM TE/g to 1208.81 mM TE/g, respectively, whose values showed a positive correlation (r ²) with the TPC and TFC. The results from the antimicrobial screening revealed that the methanolic propolis extracts in concentration of 20 mg/ml exhibited the highest inhibitory effect on the Gram-positive bacteria such as Micrococcus luteus 2YC-YT, Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 25923, Listeria monocytogenes NBIMCC 8632 and Listeria innocua ATCC 33090.

At present, there are no data in the scientific literature on studies aimed at characterizing Passiflora caerulea L. growing in Bulgaria. The present study aimed to investigate the metabolic profile and elemental composition of the leaves and pulp of this Passiflora, as well as to evaluate the antioxidant, antimicrobial and anti-inflammatory activities of its leaf and pulp extracts. The results showed that the pulp predominantly contained the essential amino acid histidine (7.81 mg g⁻¹), while it was absent in the leaves, with the highest concentration being tryptophan (8.30 mg g⁻¹). Of the fatty acids, palmitoleic acid predominated both in the pulp and in the leaves. A major sterol component was β-sitosterol. Fructose (7.50%) was the predominant sugar in the pulp, while for the leaves, it was glucose—1.51%. Seven elements were identified: sodium, potassium, iron, magnesium, manganese, copper and zinc. The highest concentrations of K and Mg were in the pulp (23,946 mg kg⁻¹ and 1890 mg kg⁻¹) and leaves (36,179 mg kg⁻¹ and 5064 mg kg⁻¹). According to the DPPH, FRAP and CUPRAC methods, the highest values for antioxidant activity were found in 70% ethanolic extracts of the leaves, while for the ABTS method, the highest value was found in 50% ethanolic extracts. In the pulp, for all four methods, the highest values were determined at 50% ethanolic extracts. Regarding the antibacterial activity, the 50% ethanolic leaf extracts were more effective against the Gram-positive bacteria. At the same time, the 70% ethanolic leaf extract was more effective against Gram-negative bacteria such as Salmonella enteritidis ATCC 13076. The leaf extracts exhibited higher anti-inflammatory activity than the extracts prepared from the pulp. The obtained results revealed that P. caerulea is a plant that can be successfully applied as an active ingredient in various nutritional supplements or cosmetic products.