Jelena S. Stanojević

The effect of extraction techniques on yield, extraction kinetics, and antioxidant activity of aqueous-methanolic extracts from nettle (Urtica dioica L.) leaves

ABSTRACT Five extraction techniques, maceration, reflux, Soxhlet, Tillepape, and ultrasonic extraction, were used to obtain the extractive matter from nettle leaves. The antioxidant activity of extracts was assessed by DPPH, FRAP, and H2O2 test, while the total phenolic and total flavonoid content was determined according to the Folin–Ciocalteu and aluminium chloride methods, respectively. Model Ponomarev and a non-stationary diffusion model through the plant material were used for modelling extraction process. The extract obtained by Soxhlet extraction, containing higher amounts of extractive matter as well as phenolic and flavonoid compounds, showed better antioxidant activity than those obtained by other extraction techniques.

Chemical Composition, Antioxidant and Antimicrobial Activity of Chamomile Flowers Essential Oil (Matricaria chamomilla L.)

Abstract The subject of this study is to determine chemical composition, antioxidant and antimicrobial activity of essential oil obtained from chamomile flowers (Matricaria chamomilla L.). The essential oil has been obtained by hydrodistillation process on semi industrial production conditions. Qualitative and quantitative composition of the oil was determined by GC-MS and GC-FID analysis. The antioxidative and antimicrobial activity of chamomile essential oil was investigated in terms of their possible application as natural antioxidants and antimicrobial agents. The obtained results proved the presence of 52 components, wherein the highest content of β-farnesene (29.8 %), α-farnesene (9.3 %), α-bisabolol and its oxide (15.7 %), chamazulene (6.4 %), germacrene D (6.2 %) and spiroether (5.6 %) is determined. The antioxidant activity was investigated by DPPH assay. Chamomile essential oil has shown the best antioxidant properties after 90 minutes of incubation with EC50 value of 2.07 mg/ml. The antimicrobial activity of chamomile essential oil was tested using the agar diffusion method wherein the essential oil has shown notably antibacterial effect with the inhibition zone in diameter from 13.33 mm (on Listeria monocytogenes) to 40.00 mm (on Staphylococcus aureus). There was no antimicrobial activity of chamomile oil on the Pseudomonas aeruginosa bacteria. Chemical composition, antioxidant and antimicrobial activity of the tested chamomile essential oil, obtained from plant material from the northwestern Republic of Srpska, indicate a significant phytomedical potential.

Benzophenone Suppression of Quercetin Antioxidant Activity towards Lipids under UV-B Irradiation Regime: Detection by HPLC Chromatography

Quercetin, a well-known flavonoid antioxidant, has been employed to control benzophenone-sensitized peroxidation of the lipid mixture in methanol solution, induced by continuous UV-B irradiation. Surprisingly, the detected quercetin antioxidant activity was almost negligible. The presented data suggests that the reason is not in its own UV-B-induced degradation but rather in its interrelationship with benzophenone during UV-B stress. On the other side of this relationship, benzophenone anticipated sensitizing role towards lipids; that is, the initiation of lipid peroxidation has been affected as well. These results, obtained by HPLC chromatography, partly confirm but partly relativize to some extent recent results obtained with the same system by spectrophotometric method.

Investigation into the potential chemical mechanism of carotenoids pro-oxidant activity with liposomes under UV- irradiation

This study focuses on the behavior of β-carotene and lutein inside multilamellar liposomes under continuous UV-irradiation. Liposomes were obtained by thin film method and carotenoids (Crts) were incorporated by mixing method at various concentrations (0.005, 0.0075, 0.02, 0.07 and 0.5 mol%). Liposomes formation and presence of Crts inside them were confirmed by SEM microscopy and FT-IR spectroscopy, respectively. The antioxidant/prooxidant activity of Crts inside liposomes was determined by Thiobarbituric Acid – Malondialdehyde (TBA-MDA) test. Investigated Crts act more or less unexpected (as pro-oxidants) inside lipid bilayer, interacting with UV-produced lipid radicals and suffering under UV-irradiation in the same time. Their pro-oxidant activity, with liposomes and under UV-irradiation, can be explained by unstable adducts formation in reaction with peroxyl radicals, or by Crts-cation radicals formation via electron transfer mechanism. Such tentatively unexpected behavior of carotenoids should be taken into account in further carotenoids based UV-filters projections in cosmetic formulation for skin protection.

Quercetin degradation induced by continuous UV-B irradiation in the presence of benzophenone

ion from lipids by triplet states of derivatized benzophenone photosensitizers, Photochemistry and Photobiology, 51(4) (1990) 389 394. [9] D. Z. Marković, L. K. Patterson, Radical processes in lipids. Selectivity of hydrogen abstraction from lipids by benzophenone triplet, Photochemistry and Photobiology, 49(5) (1989) 531 535. [10] D. Z. Marković, L. K. Patterson, Benzophenone-sensitized lipid peroxidation in linoleate micelles, Photochemistry and Photobiology, 58(3) (1993) 329 334. [11] A. Beckett, B. McClure, K. Zimmerman, Benzophenone and padimate-O protect Saccharomyces cerevisiae from UV radiation and cause little harm from UV-induced reactive chemical species, Journal of Experimental Microbiology and Immunology, 5 (2004) 37 43. [12] F. Zhang, J. Zhang, C. Tong, C. Yadong, Z. Shulin, L. Weiping Molecular interactions of benzophenone UV filters with humanserum albumin revealed by spectroscopic techniques and molecular modeling, Journal of Hazardous Materials, 263(Part 2) (2013) 618 626. [13] A. R. Ndhlala, M. Moyo, J. V. Staden, Natural antioxidants: fascinating or mythical biomolecules?, Molecules, 15(10) (2010) 6905 6930. [14] S. Tahara, A journey of twenty-five years through the ecological biochemistry of flavonoids, Bioscience, Biotechnology and Biochemistry, 71(6) (2007) 1387 1404. [15] A. Saija, A. Tomaino, D. Trombetta, M. L. Pellegrino, B. Tita, C. Messina, F. P. Bonina, C. Rocco, G. Nicolosi, F. Castelli, ”In vitro” antioxidant and photoprotective properties and interaction with model membranes of three new quercetin esters, European Journal of Pharmaceutics and Biopharmaceutics, 56(2) (2003) 167 174. [16] U. J. Joshi, A. S. Gadge, P. D’Mello, R. Sinha, S. Srivastava, G. Govil, Anti-inflammatory, antioxidant and anticancer activity of quercetin and its analogues, International Journal of Research in Pharmaceutical and Biomedical Sciences, 2(4) (2011) 1756 1766. [17] E. Falkovskaia, P. K. Sengupta, M. Kasha, Photophysical induction of dual fluorescence of quercetin and related hydroxyflavones upon intermolecular H-bonding to solvent matrix, Chemical Physics Letters, 297(1-2) (1998) 109 114. [18] B. M. Fahlman, E. S. Krol, UVA and UVB radiation-induced oxidation products of quercetin, Journal of Photochemistry and Photobiology B: Biology, 97(3) (2009) 123 131. [19] A. Zhou, O. A. Sadik, Comparative analysis of quercetin oxidation by electrochemical, enzymatic, autoxidation, and free radical generation techniques: a mechanistic study, Journal of Agricultural Food Chemistry, 56(24) (2008) 12081 12091. [20] F. T. M. C. Vicentini, S. R. Georgetti, J. R. Jabor, J. A. Caris, M. V. L. B. Bentley, M. J. V. Fonseca, Photostability of quercetin under exposure to UV irradiation, Latin American Journal of Pharmacy, 26(1) (2007) 119 124. [21] S. Dall’Acqua, G. Miolo, G. Innocenti and S. Caffieri, The photodegradation of quercetin: relation to oxidation, Molecules, 17(8) (2012), 8898 8907. [22] A. Marfak, P. Trouillas, D. P. Allais, C. A. Calliste and J. L. Duroux, Redox reactions obtained by gamma irradiation of quercetin methanol solution are similar to in vivo metabolism, Radiation Research, 159(2) (2003) 218 227. [23] A. Zhou, S. Kikandi, O. A. Sadik, Electrochemical degradation of quercetin: Isolation and structural elucidation of the degradation products, Electrochemistry Communications, 9(9) (2007) 2246 2255. [24] A. K. Timbola, C. D. de Souza, C. Giacomelli, A. Spinelli, Electrochemical oxidation of quercetin in hydro-alcoholic solution, Journal of the Brazilian Chemical Society, 17(1)

Riboflavin degradation in the presence of quercetin in methanol under continuous UV-B irradiation: the ESI–MS–UHPLC analysis

The presented work deals with continuous UV-B irradiation of riboflavin in MeOH solution, leading to its degradation under anaerobic as well as aerobic conditions (faster in the former case), which is related to riboflavin photosensitizing properties (type I photosensitizer in the first case, and type II in the other one). Addition of quercetin, a well-known antioxidant in the system causes a decrease of the (riboflavin) degradation in both cases. In anaerobic conditions it might be a consequence of quercetin antioxidant scavenging activity, while under aerobic conditions it could be related to singlet oxygen formation. The degradation dynamics—in both systems, in the presence and in the absence of quercetin—is well synchronized with dynamics formation of the two major products, lumiflavin and lumichrome.Graphical abstract

An Analysis of the Labour Productivity of the Agricultural Sector in the Republic of Serbia

Abstract One of the main objectives pursued in agriculture as the primary sector in the economy is to increase the labour productivity. In order for this objective to be achieved, it is necessary to increase agricultural production, while at the same time preserve natural resources and the environment. If the creators of development policies are to formulate effective policies and strategies, adequate information relating to all vital determinants of productivity of agriculture is required. Therefore, the Statistical Office of the Republic of Serbia annually prepares and publishes, among others, information on the value of agricultural production and the number of employees in agriculture. The aim of this paper is to examine the changes in the level of productivity of agriculture in the Republic of Serbia in the period from 2007 to 2013. It also analyses the impact of labour productivity in agriculture in the share of GDP that is realized in this sector of the national economy. Agricultural population, as one of the factors that affect productivity in agriculture is analysed in terms of education and employment. The aim is to quantify the level of productivity in agriculture, as well as to examine the interdependence between labour productivity and GDP in agriculture, in order to point to the critical determinants of productivity that require improvement. The methods used in this paper are: analysis method, synthesis method, comparison method, descriptive statistics, correlation and regression analysis. Research results show that Serbia has achieved an unenviable level of labour productivity in agriculture within the analysed period of time. Research in this study is useful for the creators and holders of the development policy for the future guidance of development policies and strategies of the agricultural sector in Serbia.