Jovana Petrović

In situ antioxidant and antimicrobial activities of naturally occurring caffeic acid, p-coumaric acid and rutin, using food systems.

BACKGROUND Three pure compounds that naturally occur in plants were of particular interest to our study regarding the possibility of using them as food preservatives: p-coumaric acid (found in peanuts, tomatoes, carrots, garlic, wine, vinegar, etc.), caffeic acid (found in argan oil, oats, wheat, rice and olive oil) and rutin (found in asparagus, citrus fruits, berries, apple, apricot, asparagus, beef and beer). In the following study we investigated in situ antioxidant and antimicrobial activities of three pure compounds, namely caffeic acid, p-coumaric acid and rutin, naturally occurring in plants. RESULTS Two food systems were used in order to obtain information on how these compounds react in actual food systems rather than microbiological media. The results indicated good antioxidant activity in in situ food systems. For tested phenolic compounds it was further shown that they successively inhibited the development of the isolated food contaminant Staphylococcus aureus in chicken soup. Panelist found that organoleptic characteristics of chicken soup and pork meat improved after treatment with phenolics. CONCLUSION Our findings alone, along with the potential use of phenolic compounds that are widespread in nature, may imply their potential use as preservatives in the food industry.

Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission

Several groups of authors have analyzed Fermi LAT data in a region around the Galactic Center finding an unaccounted gamma-ray excess over diffuse backgrounds in the GeV energy range. It has been argued that it is difficult or even impossible to explain this diffuse emission by the leading astrophysical candidates - millisecond pulsars (MSPs). Here we provide a new estimate of the contribution to the excess by a population of yet unresolved MSP located in the bulge of the Milky Way. We simulate this population with the GALPLOT package by adopting a parametric approach, with the range of free parameters gauged on the MSP characteristics reported by the second pulsar catalogue (2PC). We find that the conclusions strongly depend on the details of the MSP luminosity function (in particular, its high luminosity end) and other explicit or tacit assumptions on the MSP statistical properties, which we discuss. Notably, for the first time we study the importance of the possible secondary emission of the MSPs in the Galactic Center, {i.e. the emission via inverse Compton losses of electrons injected in the interstellar medium. Differently from a majority of other authors, we find that within current uncertainties a large if not dominant contribution of MSPs to the excess cannot be excluded. We also show that the sensitivities of future instruments or possibly already of the latest LAT data analysis (Pass 8) provide good perspectives to test this scenario by resolving a significant number of MSPs.

Sensitivity of LPGs in PCFs Fabricated by an Electric Arc to Temperature, Strain, and External Refractive Index

Sensing properties of long-period gratings (LPGs) fabricated in photonic crystal fibers by an electric arc are explained and quantified by semianalytical and numerical models. In particular, the gratings insensitivity to temperature and simultaneous sensitivity to strain and refractive index are simulated. The modeling procedure is generalized so that it can be applied to a wide range of LPGs in various fibers

Sour cherry pomace extract encapsulated in whey and soy proteins: Incorporation in cookies.

One of the potential sources of valuable bioactives is pomace, a by-product from fruit juice processing industry. In the presented study, bioactive compounds extracted from cherry pomace, encapsulated in whey and soy proteins, have been incorporated in cookies, replacing 10% (WE10 and SE10) and 15% (WE15 and SE15) of flour. Total polyphenols, anthocyanins, antioxidant activity and colour characteristics of enriched cookies were followed during 4 months of storage. Total polyphenols of WE10, SE10, WE15 and SE15 have shown a slight increase (23.47, 42.00, 4.12 and 1.16%, respectively), while total anthocyanins (67.92, 64.33, 58.75 and 35.91%, respectively) and antioxidant activity (9.31, 24.30, 11.41 and 12.98%, respectively) decreased. Colour parameters (L(∗), a(∗) and b(∗)) of cookies were influenced by the colour of encapsulates. Fortified cookies received satisfactory sensory acceptance as well. Encapsulated sour cherry pomace bioactives have positively influenced functional characteristics of fortified cookies and their preservation.

Non-invasive respiratory monitoring using long-period fiber grating sensors

In non-invasive ventilation, continuous monitoring of respiratory volumes is essential. Here, we present a method for the measurement of respiratory volumes by a single fiber-grating sensor of bending and provide the proof-of-principle by applying a calibration-test measurement procedure on a set of 18 healthy volunteers. Results establish a linear correlation between a change in lung volume and the corresponding change in a local thorax curvature. They also show good sensor accuracy in measurements of tidal and minute respiratory volumes for different types of breathing. The proposed technique does not rely on the air flow through an oronasal mask or the observation of chest movement by a clinician, which distinguishes it from the current clinical practice.

Laetiporus sulphureus, edible mushroom from Serbia: investigation on volatile compounds, in vitro antimicrobial activity and in situ control of Aspergillus flavus in tomato paste.

The volatile compounds of fruiting bodies of wild Laetiporus sulphureus (Bull.) Murrill, growing on willow trees from Serbia, were isolated and extracted using methanol, acetone and dichloromethane and investigated by GC/MS-SPME. A total of 56 components were identified in the extracts. Hydrocarbons predominated (76.90%, 77.20%, and 43.10%) in dichloromethane, acetone and methanol extracts, respectively. Fatty acids, esters and sesquiterpenes were present in amounts equal or lower than 2.00%. Ketones were represented with moderate amount with the exception of methanol extract where it reached as much as 28.90% of the total investigated compounds. Extracts were also tested for antimicrobial activity with and without the addition of food additive - potassium disulfite in vitro against eight bacterial and eight fungal species, and in situ in tomato paste against Aspergillus flavus. All the tested extracts showed good antimicrobial activity, but methanol extract with addition of E224 showed the best antimicrobial activity in vitro. In situ results indicate complete inhibition of A. flavus growth in tomato paste after 15 days of the treatment. This study is the first report on volatile composition of L. sulphureus growing wild in Serbia. We describe for the first time the application of its extract as antifungal food preservative.

Femtosecond laser microfabrication of subwavelength structures in photonics

This paper describes experimental and numerical results of the plasma-assisted microfabrication of subwavelength structures by means of point-by point femtosecond laser inscription. It is shown that the spatio-temporal evolution of light and plasma patterns critically depend on input power. Subwavelength inscription corresponds to the supercritical propagation regimes when pulse power is several times self-focusing threshold. Experimental and numerical profiles show quantitative agreement.

4-Thiazolidinone derivatives as potent antimicrobial agents: microwave-assisted synthesis, biological evaluation and docking studies

As a part of our ongoing research in the development of new antimicrobials, herein, we report the synthesis of ten compounds which combine three bioactive moieties: thiazole, adamantane and 4-thiazolidinone. Evaluation of their antibacterial activity revealed that the newly synthesized compounds exhibited remarkable growth inhibition of a wide spectrum of Gram-positive bacteria, Gram-negative bacteria and fungi. The majority of the compounds displayed greater antibacterial activity than the reference drugs (ampicillin and streptomycin), while the antifungal activity was significantly higher than that of the reference drugs bifonazole and ketoconazole. Additionally, the title compounds were screened for HIV-1 reverse transcriptase inhibitory activity, showing no significant activity. Moreover, docking studies were performed in order to explore possible binding modes at the MurB protein of S. aureus.

Bound states in continuum of complex potentials generated by supersymmetric quantum mechanics

It is shown that bound states in continuum can be generated by applying supersymmetric quantum mechanics to real potentials in such a way that the transformed potential becomes complex. Three cases of the initial potential are considered in more detail: flat potential, step potential and rectangular quantum well. The conditions are found for the existence of bound state in continuum in these cases, as well as the expressions for the wavefunction of this state and the corresponding complex potential in analytic form.

Lipid and fatty acid profile of the edible fungus Laetiporus sulphurous. Antifungal and antibacterial properties

Laetiporus sulphureus is a saprophyte belonging to a specific group of wood-decomposing Basidiomycetes growing on deciduous trees. This fungus has been characterized as a herbal medicine and is also known for its antimicrobial properties. In the present study, high energy extraction techniques using different solvents were compared to obtain maximum yield of the edible fungus Laetiporus sulphureus total lipids. The lipid classes and fatty acid composition of the fruiting bodies’ total lipids has been studied using GC-FID and Iatroscan TLC-FID analysis. Among the lipids, the neutral lipids predominated followed by phospholipids and glycolipids. Triglycerides were the most abundant in the neutral lipid fraction, whereas phosphatidylcholine in phospholipids. The existence of relatively high amount of sterols may be correlated to fungus pharmaceutical properties. Total lipids were found to contain high unsaturated degree fatty acids (UFA/SFA>3.4) and dominated of C18:2ω-6, C18:1ω-9 and C16:0 fatty acids. Antibacterial and antifungal properties of mushrooms’ lipid extracts from two different solvents were also examined. Results indicated that hexane extracts possessed better antifungal and slightly better antibacterial activity compared to chloroform extracts though both were less active than the commercial antimicrobial agents.