Vesna Nikolić

Antioxidant activity and total phenolic and flavonoid contents of Hieracium pilosella L. extracts.

The antioxidant activity of water, ethanol and methanol Hieracium pilosella L. extracts is reported. The antioxidative activity was tested by spectrophotometrically measuring their ability to scavenge a stable DPPH• free radical and a reactive hydroxyl radical trapped by DMPO during the Fenton reaction, using the ESR spectroscopy. Total phenolic content and total flavonoid content were evaluated according to the Folin-Ciocalteu procedure, and a colorimetric method, respectively. A HPLC method was used for identification of some phenolic compounds (chlorogenic acid, apigenin-7-O-glucoside and umbelliferone). The antioxidant activity of the investigated extracts slightly differs depending on the solvent used. The concentration of 0.30 mg/mL of water, ethanol and methanol extract is less effective in scavenging hydroxyl radicals (56.35, 58.73 and 54.35%, respectively) in comparison with the DPPH• radical scavenging activity (around 95% for all extracts). The high contents of total phenolic compounds (239.59–244.16 mg GAE/g of dry extract) and total flavonoids (79.13–82.18 mg RE/g of dry extract) indicated that these compounds contribute to the antioxidative activity.

A survey study of critical success factors in agile software projects in former Yugoslavia IT companies

Determining the factors that have an influence on the success of the software development projects has been the focus of extensive research for more than 30 years. In recent years agile methodology of software development has become the dominant one for all kinds of software development projects. In this paper we present the results of empirical study for determining critical factors that influence the success of agile software projects which we conducted among senior developers and project managers from IT companies located in the former Yugoslavia countries within South Eastern Europe (SEE) region. This study is inspired by the similar study conducted 5 years ago (Chow and Cao, 2008). With this study we were not able to confirm the model developed in the previous study. Moreover it disconfirmed not only part of the factors, but very much questioned the whole scheme. However, we were able to shed additional light regarding agile software development in former Yugoslavia countries from SEE region as a reference region for investigating outsourced projects done in agile way.

Novel Microwave-Assisted Synthesis of Poly(D,L-lactide): The Influence of Monomer/Initiator Molar Ratio on the Product Properties

Poly(D,L-lactide) synthesis using tin(II) 2-ethylhexanoate initiated ring-opening polymerization (ROP) takes over 30 hours in bulk at 120 °C. The use of microwave makes the same bulk polymerization process with the same initiator much faster and energy saving, with a reaction time of about 30 minutes at 100 °C. Here, the poly(lactide) synthesis was done in a microwave reactor, using frequency of 2.45 GHz and maximal power of 150 W. The reaction temperature was controlled via infra-red system for in-bulk-measuring, and was maintained at 100 °C. Different molar ratios of monomer and initiator, [M]/[I], of 1,000, 5,000 and 10,000 were used. The achieved average molar masses for the obtained polymers (determined by gel permeation chromatography) were in the interval from 26,700 to 112,500 g/mol. The polydispersion index was from 2.436 to 3.425. For applicative purposes, the obtained material was purified during the procedure of microsphere preparation. Microspheres were obtained by spraying a fine fog of polymer (D,L-lactide) solution in tetrahydrofuran into the water solution of poly(vinyl alcohol) with intensive stirring.

ALLICIN AND RELATED COMPOUNDS: BIOSYNTHESIS, SYNTHESIS AND PHARMACOLOGICAL ACTIVITY †

In this review, the biosynthesis of allicin (allyl thiosulfinate) by enzymatic transformation of alliin and various methods of its synthesis with detailed investigation of mechanisms and kinetics are summarized. A convenient method is also described for determination of allicin stability and the utility of the inclusion complexes of this pharmacologically active agent with β-cyclodextrins in increasing its stability. Allicin is the initial precursor for the production of ajoene ((E)- and (Z)-4,5,9-trithiadodeca- 1,6,11-triene 9-oxides) and vinyldithiin (2-vinyl-4H-1,3-dithiin, and 3-vinyl-4H-1,2- dithiin), which are more stable and show various pharmacological effects. The mechanisms of allicin transformations to these compounds are given in detail. Finally, the data on the pharmacological effects of allicin and its transformation products, ajoene and vinyldithiin, are presented.

Thermal degradation, antioxidant and antimicrobial activity of the synthesized allicin and allicin incorporated in gel

The main carriers of the pharmacological activity of garlic (Allium sativum L.) are organic sulfur compounds, the most important among them being allicin, a sulfenic acid thioester, or allylthiosulfonate. In this paper, the identification of synthesized and purified allicin was determined by using various spectroscopic methods (UV/VIS, FTIR, NMR). A HPLC method was developed for the detection and determination of the allicin content. The thermal degradation of allicin by using FTIR method was monitored. The method for the production of allicin gel based on Carbopol 940 (poly(acrylic acid)) was elaborated. The antimicrobial activity of pure allicin and allicin incorporated into gel by using a disk diffusion method was determined. In order to determine the antioxidant activity of allicin DPPH test was done and it was proved that with low concentrations (1 mgcm-3) a high DPPH radicals scavenging capacity (90%) was achieved.

Transformation of Synthetic Allicin: The Influence of Ultrasound, Microwaves, Different Solvents and Temperatures, and the Products Isolation

The transformation of the synthesized allicin, using conventional method, the influence of ultrasound and microwaves, in different organic solvents (acetonitrile, acetone, methanol, and chloroform), at various temperatures (room temperature, 45°C, and 55°C) was investigated. Allicin degradation kinetic was monitored by HPLC. Allicin transformation under the effect of microwaves is faster than transformations performed under the influence of ultrasound or by conventional method. Increase of the temperature accelerates allicin transformation. Pharmacologically active compounds of (E)-ajoene, (Z)-ajoene, 3-vinyl-4H-1,2-dithiin, 2-vinyl-4H-1,3-dithiin, and diallyl disulfide were isolated from the mixture of transformation products of allicin under the influence of microwaves in methanol at 55°C, which is according to kinetic parameters (highest values of the order of reaction and the lowest activation energy) the optimal method.

Inclusion complexes of amlodipine besylate and cyclodextrins

AbstractIn this paper the procedure for the preparation of inclusion complexes of amlodipine besylate with β-cyclodextrin (β-CD) and 2-hydrohypropyl-β-cyclodextrin (HPβ-CD) and their structural characterization was described. Molecular inclusion complexes of amlodipine besylate are prepared by the coprecipitation method and characterised by the application of spectroscopic methods FTIR, 1H-NMR and XRD. The photosensitivity of amlodipine besylate in the inclusion complexes was also determined with respect to uncomplexed agent. DSC curves indicate the loss of the clear peak due to melting of amlodipine besylate at about 200°C, while on XR diffractograms certain reflections are lost belonging to amlodipine besylate in complexes. This indicates its inclusion in the vacancies of the host. The inclusion of amlodipine besylate with cyclodextrins increases the stability, i.e. decreases the photosensitivity of amlodipine besylate.

Inclusion complexes of sulfanilamide with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin

Sulfanilamide belongs to the group of drugs that have a bacteriostatic effect on different pathogenic microorganisms. This activity originates from the competitive antagonism with p-aminobenzoic acid, which is an integral part of folic acid. The safe use of sulfanilamide is limited due to poor solubility in the aqueous medium. Therefore, the aim of this paper is the synthesis of sulfanilamide, as well as preparing and structural characterization of its inclusion complexes with cyclodextrins. The crude sulfanilamide was obtained in the synthesis between acetanilide and chlorosulfonic acid according to the standard procedure. The synthesized sulfanilamide was recrystallized from water in order to obtain the satisfactory purity of the substance. Sufanilamide was complexed with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin by the co-precipitation method. A molecular encapsulation of sulfanilamide was confirmed by using FTIR, 1H-NMR, XRD and DSC methods. Phase-solubility techniques were used to assess the formation of the inclusion complex between sulfanilamide and cyclodextrins. The photostability of sulfanilamide and its inclusion complexes was estimated by UVB irradiation in a photochemical reactor by applying the UV–Vis method. Based on the UV–Vis analysis, sulfanilamide:2-hydroxypropyl-β-cyclodextrin complex was presented as more photostable than sulfanilamide:β-cyclodextrin complex and sulfanilamide. The obtained results enable the potential use of these inclusion complexes for the preparation of oral formulations due to the enhanced solubility of sulfanilamide.

The effect of hydrodistillation techniques on yield, kinetics, composition and antimicrobial activity of essential oils from flowers of Lavandula officinalis L.

The essential oils from flowers of Lavandula officinalis L. (L. officinalis L.= L. angustifolia Mill.) were obtained by two hydrodistillation techniques: standard (technique I) and modified (technique II) Clevenger hydrodistillation. The yield, hydrodistillation kinetics, composition and antimicrobial activity of essential oils were investigated. The higher yield of oil was obtained by hydrodistillation technique II. The new analytical hydrodistillation kinetics model of essential oil from Lavandulae flowers was defined. The essential oil composition was analyzed by gas chromatography–mass spectroscopy (GC–MS). There were differences in chemical compositions of the oils obtained by different techniques. Antimicrobial activity of essential oil obtained by technique I and II against Salmonella enteritidis, Klebsiella pneumoniae, Staphylococcus aureus, Enterococcus faecalis, Candida albicans and Aspergillus niger was the same, while the activity against Escherichia coli and Pseudomonas aeruginosa was slightly different.

The protection of Nifedipin from photodegradation due to complex formation with β-cyclodextrin

AbstractThe inclusion complex β-cyclodextrin:nifedipin was prepared in solid state by coprecipitation with 1:1 mol ratio. The structure of the obtained complex and nifedipin was characterized by use of X-ray diffraction (XR), infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) methods. The photodegradation of nifedipin and the β-cyclodextrin:nifedipin inclusion complex in solid state was monitored under natural daylight by infrared spectroscopy, whereby the free nifedipin degraded four to five times faster than the complexed nifedipin. The photodegradation products of both free and complexed nifedipin, formed during irradiation at 350 nm (with corresponding energy flux of 18 W m−2) were monitored by liquid chromatography during various time intervals. The speed of formation of nitroso- and nitro-phenyl derivatives by nifedipin irradiation was significantly higher than those of complexed nifedipin irradiation, which indicates its increased photostability in the inclusion complex. The effect on this property is significant because it contributes both to the improvement of the therapeutic effect of nifedipin and to the safer application thereof.