The antioxidative, antimicrobial and antiproliferative potentials of the methanol extracts of the lichen species Parmelia sulcata, Flavoparmelia caperata, Evernia prunastri, Hypogymnia physodes and Cladonia foliacea were evaluated. The total phenolic content of the tested extracts varied from 78.12 to 141.59 mg of gallic acid equivalent (GA)/g of extract and the total flavonoid content from 20.14 to 44.43 mg of rutin equivalent (Ru)/g of extract. The antioxidant capacities of the lichen extracts were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals scavenging. Hypogymnia physodes with the highest phenolic content showed the strongest DPPH radical scavenging effect. Further, the antimicrobial potential of the lichen extracts was determined by a microdilution method on 29 microorganisms, including 15 strains of bacteria, 10 species of filamentous fungi and 4 yeast species. A high antimicrobial activity of all the tested extracts was observed with more potent inhibitory effects on the growth of Gram (+) bacteria. The highest antimicrobial activity among lichens was demonstrated by Hypogymnia physodes and Cladonia foliacea. Finally, the antiproliferative activity of the lichen extracts was explored on the colon cancer adenocarcinoma cell line HCT-116 by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) viability assay and acridine orange/ethidium bromide staining. The methanol extracts of Hypogymnia physodes and Cladonia foliacea showed a better cytotoxic activity than the other extracts. All lichen species showed the ability to induce apoptosis of HCT-116 cells.

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Negative effects of available antibiotics and the constant development of bacterial resistance motivate a search for new antimicrobial agents. Aromatics plants have traditionally been used as antibacterial agents and are well accepted today as a source of antioxidants. The present study evaluated the antibacterial activities and antioxidant capacity of eight aromatic plants, indigenous to the flora of the Balkan Peninsula, which are used as medicinal plants in traditional medicine. The plants studied were Hyssopus officinalis, Angelica pancicii, Angelica sylvestris, Laserpitium latifolium, Achillea grandifolia, Achillea crithmifolia, Artemisia absinthium and Tanacetum parthenium. The antimicrobial activities of methanolic extracts of the plant tissues against 16 bacterial isolates of Escherichia coli, Pseudomonas aeruginosa, Klebsiella sp., Proteus mirabilis, Acinetobacter sp., Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae and Enterococcus faecalis were investigated using a microwell dilution assay. Minimal inhibitory concentration (MIC) of the extracts ranged from 6.3 to 100 mg mL -1 , and minimal bactericidal concentration (MBC) ranged from 12.5 to 100 mg mL -1 . Antioxidant potential of the extracts was analyzed as contents of total phenols and flavonoids; radical scavenging activity by the ABTS • + and DPPH • methods, and reducing power by the iron (III) to iron (II) reduction assay, and the ferric reducing antioxidant power assay (FRAP). Results of antioxidative activities from the 4 methods demonstrated similar sequence of activity: A. crithmifolia > A. grandifolia > H. officinalis > A. absinthium > T. parthenium > L. latifolium > A. pancicii > A. sylvestris. The total content of polyphenols and flavonoids in the methanol extracts of the studied species positively correlated with their antioxidant properties, confirming their major role in antioxidant activity of these species.

The purpose of this study was to investigate the inhibitory/bactericidal activity and cell membrane effects of the hydrodistilled essential oil of Inula helenium L. roots against Staphylococcus aureus. Additionally, detailed chemical investigation was done in order to pinpoint the most active oil constituents and also the parts of these molecules responsible for their antimicrobial effect. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using the broth microdilution method. The membrane-active nature of this oil was investigated by measuring the culture turbidity, leakage of phosphates, and 260-nm-absorbing material, together with lysis of the exposed cells. Finally, the effect of the oil on the cells was visualized using scanning electron microscopy (SEM). The chemical composition of the essential oil was analyzed using gas chromatography-mass spectrometry (GC-MS) and preparative medium-pressure liquid chromatography (MPLC). Chemical modification of the oil was performed using catalytic hydrogenation (H(2), Pd/C) and reduction with NaBH(4). The MIC and MBC values were 0.01 μl mL(-1) and 0.02 μl mL(-1), respectively. Membrane damage was demonstrated through increased permeability (phosphates and nucleic acid leakage), followed by lysis of the exposed cells, captured on SEM images. The most active constituents were alantolactone, isoalantolactone, and diplophyllin. The essential oil showed very potent antistaphylococcal activity, with obvious membrane-damaging effects. Sesquiterpene lactones were found to be the most active principles of the oil, whose eudesmane core olefinic bonds, along with the α,β-methylene-lactone ring, are essential structural parts responsible for the exhibited antimicrobial activity.

Melilotus albus Medic. and Dorycnium herbaceum Vill. (Fabaceae) acetone, ethyl acetate, and ethanol extracts were investigated for their in vitro antimicrobial, antibiofilm, and antioxidant activity with quantification of phenolic compound contents. In general, D. herbaceum extracts showed better antibacterial and antioxidant activity than M. albus extracts. Bacteria Bacillus subtilis, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa, and Proteus mirabilis were the most susceptible with the minimum inhibitory concentrations (MICs), determined by microdilution method, between 1.25-10 mg/mL. Antifungal activity was lower with the detectable MICs at 10 mg/mL and 20 mg/mL. The plant extracts, using the crystal violet assay, inhibit P. aeruginosa biofilm formation in concentration range from 5 mg/mL to 20 mg/mL whereas the effect on mature bacterial biofilm was lower. The antioxidant activity was evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radicals scavenging and reducing power model systems. The intensity of DPPH radicals scavenging activity, expressed as half maximal effective concentration (EC) values, was from 84.33 μg/mL to >1000 μg/mL. The extracts demonstrated reduced power in a concentration-dependent manner, with ethanol extract as the most active. The total phenols, flavonoids, and proanthocyanidins were determined spectrophotometrically while total extractable tannins were obtained by precipitation method. The phenolic compounds showed differences in their total contents depending on solvents polarities and plant species. Although the plants M. albus and D. herbaceum have not yet been fully explored, these results contribute better understanding of their biotic properties and potential application as antimicrobial and antioxidant agents.

In this article, the presence and physiological characteristics of lactic acid bacteria (LAB) isolated from traditionally made cheese from Southeastern Serbia were examined. Three samples, from different households, were obtained in spring. The screening of antagonistic potentials, using agar‐well diffusion method, was evaluated. Briefly, three different genera of LAB (Enterococcus [32%], Lactococcus [53%], and Lactobacillus [15%]) were identified. The members of the genus Enterococcus were Enterococcus faecium and Enterococcus faecalis. The member of genus Lactococcus was Lactococcus lactis subsp. lactis var. diacetylactis. The members of genus Lactobacillus were Lactobacillus fermentum, Lactobacillus plantarum, and Lactobacillus paracasei subsp. paracasei. The antagonism of LAB on the growth of Escherichia coli ATCC 25922, Proteus mirabilis ATCC 12453, Klebsiella oxytoca KGPMF1, Klebsiella ornithinolytica KGPMF8, and Aeromonas hydrophila was examined. All tested isolates inhibited the growth of at least one indicator strain with growth inhibition zone from 10 to 21 mm. Results indicated that LAB demonstrated the potential of food biopreservation. Practical applications Traditionally made cheeses represent excellent source of unexplored microflora, especially of autochthonous lactic acid bacteria (LAB). In cheese from Sokobanja, the isolated LAB genera were Lactobacillus sp., Lactococcus sp., and Enterococcus sp. Also, the physiological activity of LAB, as well as their interaction with enterobacteria, which also was isolated from the mentioned cheese, was investigated. The results of this study demonstrated potential of LAB to interact agonistically with the growth of enterobacteria, which was important due to the well‐known fact that enterobacteria could affect the organoleptic properties of cheese. LAB showed potential of food biopreservation. Further investigation should include antagonistic potential related to food‐borne bacteria and the mechanisms of action.

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The aim of this work was to investigate the antibacterial activity of aqueous extracts of the species Salvia officinalis L. and its synergistic action with the preservatives sodium nitrite, sodium benzoate and potassium sorbate in vitro against selected food spoiling bacteria. Synergism was assessed by the checkerboard assay method and quantitatively represented by the FIC index. Synergistic action was established for aqueous extract/sodium benzoate, aqueous extract/potassium sorbate, aqueous extract/sodium nitrite combinations. Synergism was detected in relation to: Agrobacterium tumefaciens, Bacillus subtilis and Proteus sp. Synergism was established at plant extract and preservative concentrations corresponding up to 1/8 MIC values