Sonja Djilas

Assessment of polyphenolic content and in vitro antiradical characteristics of apple pomace

Apple pomaces, a by-product in the apple juice processing, were subjected to evaluation as potential sources of antioxidant phytochemicals on the basis of their total content of phenolics (from 4.22 to 8.67mg/g), total flavonoids (from 0.45 to 1.19mg/g) and total flavan-3-ols (from 2.27 to 9.51mg/g), and in vitro antiradical activities. Some individual phenolic compounds including caffeic and chlorogenic acids, (+)-catechin and (-)-epicatechin, rutin, quercetin glycosides and phloridzin were identified and quantified by HPLC. The antiradical activity of apple pomaces was tested by measuring their ability to scavenge DPPH and hydroxyl radicals by ESR spectroscopy. The highest DPPH (EC50(DPPH)=6.33mg/ml) and hydroxyl (EC50(OH)=26.11mg/ml) radical scavenging activities were obtained in the case of Reinders pomace. The regression analysis produced moderate to high correlation coefficients between the antiradical activities (1/EC50(DPPH) and 1/EC50(OH)), and total phenolics, total flavonoids, total flavan-3-ols, and some individual phenolic compounds.

By-products of fruits processing as a source of phytochemicals

The processing of fruits results in high amounts of waste materials such as peels, seeds, stones, and oilseed meals. A disposal of these materials usually represents a problem that is further aggravated by legal restrictions. Thus new aspects concerning the use of these wastes as by-products for further exploitation on the production of food additives or supplements with high nutritional value have gained increasing interest because these are high-value products and their recovery may be economically attractive. It is well known that by-products represent an important source of sugars, minerals, organic acid, dietary fibre and phenolics which have a wide range of action which includes antitumoral, antiviral, antibacterial, cardioprotective and antimutagenic activities. This review discusses the potential of the most important by-products of apple, grape and citrus fruits processing as a source of valuable compounds. The relevance of this topic is illustrated by a number of references.

Synthesis of some heterocyclic aminoimidazoazarenes

Abstract The reaction mechanism of the synthesis of 2-amino-3,4-dimethylimidazo(4,5-f)-quinoline and 2-amino-3,4,8-trimethylimidazo(4,5-f)quinoxaline as compounds of the new class of mutagenic heterocyclic amines, amino-imidazoazarenes, in the reaction between aldoses, amino acids and creatinine, has been studied. The reaction involves two reaction steps: (a) the initial step and (b) the steady-state reaction step. The initial step depends on the existence and kinetics of the Maillard and Strecker reactions and pyridine and pyrazine free radical formations. Stabilization of the formed free radicals occurs in the steady-state step, giving pyridine and pyrazine derivatives. These compounds reacted with creatinine and formed amino-imidazoazarenes. The proposed reaction mechanism of the formation of the amino-imidazoazarenes has been studied by Electron Spin Resonance (ESR), 1 H Nuclear Magnetic Resonance ( 1 H NMR) spectroscopy and Mass spectrometry (MS).

Radical Scavenging, Antibacterial, and Antiproliferative Activities of Melissa officinalis L. Extracts

The aromatic herb Melissa officinalis L. can be used as an easily accessible source of natural antioxidants and as a possible food supplement and as a phytochemical. Radical scavenging, antibacterial, and antiproliferative activities of petroleum ether, chloroform, ethyl acetate, n-butanol, and water extracts of M. officinalis L. extracts were investigated. The results of antioxidative activity, obtained by electron spin resonance spectroscopy, confirmed that investigated extracts suppressed the formation of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, and lipid peroxyl radicals in all investigated systems in a dose-dependent manner. The maximum DPPH and hydroxyl radical scavenging activities (SA(DPPH) = SA(OH) = 100%) were achieved in the presence of n-butanol extract at concentrations of 0.4 mg/mL and 0.5 mg/mL, respectively. The highest lipid peroxyl scavenging activity (93.20%) was observed at a higher concentration (5 mg/mL) of n-butanol extract in the lipid peroxidation system. The most effective antibacterial activities were expressed by petroleum ether and ethyl acetate extracts on Sarcina lutea. Chloroform extract showed the strongest antiproliferative effect with 50% inhibitory concentration values of 0.09 mg/mL and 0.10 mg/mL for HeLa and MCF-7 cell lines, respectively. The present study demonstrated the high phenolic content and radical scavenging, antibacterial, and antiproliferative activities of extracts of M. officinalis L. originating from Serbia.

Isolation, characterization and antioxidative activity of C-phycocyanin from Limnothrix sp. strain 37-2-1

C-phycocyanin (C-PC) is a blue colored accessory photosynthetic pigment found in cyanobacteria. Some of the medicinal properties of Spirulina have been attributed to this pigment, which includes anticancer, antioxidant, and anti-inflammatory activity. We have screened cyanobacteria isolated from freshwater habitats in Florida for their high content of C-PC. Of 125 strains tested, one filamentous strain identified as Limnothrix sp. was selected for further research. This strain produced 18% C-PC of total dry biomass. Here we describe a simple method for obtaining C-PC of high purity without the use of ion exchange chromatography. The procedure is based on pigment precipitation from the cell lysate with an appropriate concentration of ammonium sulfate, then purification with activated carbon and chitosan, followed by a sample concentration using tangential flow filtration. We have shown that when the lower concentration of ammonium sulfate was used, C-PC with higher purity index was recovered. Characterization of C-PC from Limnothrix showed that it had an absorbance maximum at 620nm and fluorescence at 639nm. The molecular mass of intact C-PC was estimated to be ~50kDa with α and β subunits forming dimmers. When C-PC content per unit biomass was compared to that of marketed Spirulina powder, we found that Limnothrix was superior. C-phycocyanin from Limnothrix had an antioxidative activity on DPPH free radicals similar to that found in a natural antioxidant - rutin.

Antiradical, antimicrobial and cytotoxic activities of commercial beetroot pomace

The by-product of food processing is often utilized as feed, and for the preparation of dietary fiber and biofuel. However, these products are also promising sources of bioactive antioxidants and color giving compounds, which could be used as additives in the food, pharmaceutical and cosmetic industry. The aim of this study was to investigate the phytochemical profile, and the antiradical, antimicrobial and cytotoxic activities of industrial beetroot pomace extract (BPE). The content of phenolics (45.68 mg gallic acid equivalents g(-1)), flavonoids (25.89 mg rutin equivalents g(-1)) and betalains (4.09 mg betanin g(-1); 7.32 mg vulgaxanthin I g(-1)) were determined spectrophotometrically. The antiradical activity on DPPH (EC(50)(DPPH·) = 0.0797 mg ml(-1)), hydroxyl (EC(50)(·OH) = 0.0655 mg ml(-1)) and superoxide anion (EC(50)(O2·-) = 1.0625 mg ml(-1)) radicals were measured by electron spin resonance (ESR) spectroscopy. The antimicrobial activity was determined using the agar-well diffusion method. Gram(-) bacteria (Salmonella typhimurium, Citrobacter freundii) and Gram(+) bacteria, (Staphylococcus aureus, Staphylococcus sciuri, Bacillus cereus) showed high susceptibility, while yeasts and moulds were resistant. BPE exhibits cytotoxic properties against Ehrlich carcinoma (EAC) cells in vivo due to induction of oxidative stress. The largest decreases in EAC cell numbers were observed in the pre-treated male (approximately 53%) and female (approximately 47%) mice, and also the EAC cell viability was decreased after administration of BPE. The activities of the antioxidant enzymes, xanthine oxidase (XOD) and peroxidase (Px), were significantly different between the untreated EAC control group and all other groups that were treated with BPE. The XOD and Px activities were very low in untreated malignant cells, but increased significantly after administration of BPE. Our results show that BPE holds promise in the food industry as a source of bioactive compounds.

HPLC Screening of Phenolic Compounds in Winter Savory (Satureja montana L.) Extracts

Abstract Phenolic compounds in winter savory (Satureja montana L.) extracts were analysed by HPLC with diode array detection on reversed phase, C8 columns. Gradient elution with acetonitrile‐acetic acid‐water mixture gave complete separation of all phenolic acids and flavanols of interest. The identified phenolic acids and flavanols, as well as tentatively identified phenolic acids in ethyl acetate and n‐butanol extracts, were quantified. Total content of phenolic acids in ethyl acetate and n‐butanol extracts was 47.59 and 96.70 µg/g, respectively. Flavanols, (±)‐catechin and (−)‐epicatechin were present in ethyl acetate extract in quantities of 622.47 and 16.29 µg/g, respectively, while n‐butanol extract contained these flavanols in extent of 239.08 and 199.82 µg/g.

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.

Tomato waste: Carotenoids content, antioxidant and cell growth activities.

The carotenoid content, antioxidant and cell growth activities of tomato waste extracts, obtained from five different tomato genotypes, was investigated. High performance liquid chromatography was used to identify and quantify the main carotenoids present in tomato waste extracts. The antioxidant activity of tomato waste extracts was tested using spectrophotometric methods, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and reducing power assay. The highest DPPH scavenging activity (IC50 = 0.057 mg/ml) was obtained for Bačka extract. The Knjaz extract showed the best reducing power (IC50 = 2.12 mg/ml). Cell growth effects were determined in HeLa, MCF7 and MRC-5 cell lines by sulforhodamine B test. Anti-proliferative effects were observed in all cell lines at higher concentrations (⩾ 0.125 mg/ml). The carotenoid contents exhibited a strong correlation with antioxidant and anti-proliferation activity. The results obtained indicated that tomato waste should be regarded as potential nutraceutic resource and may be used as a functional food ingredient.

Naturally Occurring Phenolic Compounds as Inhibitors of Free Radical Formation in the Maillard Reaction

The influence of naturally occurring phenolic compounds, ellagic acid, 2, 3,7, 8-tetrahydroxy[1]-benzopyrano-[5, 4,3-cde][1]-benzopyran-5, 10-dione, gallic acid, 3, 4,5-trihydroxybenzoic acid, ferulic acid 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid and syringic acid, 4-hydroxy-3, 5-dimethoxybenzoic acid, as inhibitors of the formation of 1, 4-pyrazine cation free radical and pyrazine derivatives in the Maillard reactions between D(+)-glucose and 2-, 3- or 4-aminobutanoic acid, respectively, have been studied by electron spin resonance (ESR) spectroscopy. The effect of phenolic compounds on the formation of amino-imidazoazarenes, a new class of mutagenic heterocyclic amines, which are products of the Maillard reaction in the presence of creatinine, has been studied by HPLC.