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Computers & Chemical Engineering. 01/2011; 35:2284-2293.
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ABSTRACT: This paper presents a comparative study of the anti-oxidant and anti-microbial activities, total phenolic compounds and total flavonoids in extracts obtained from houseleek (Sempervivum marmoreum L.) leaves by the classical (maceration), ultrasonic and Soxhlet extraction (CE, UE and SE, respectively). The extract obtained by the CE contained higher amounts of phenolic and flavonoid compounds and showed a better antioxidant activity than those obtained using other two techniques. All the extracts, independent of the extraction technique applied, showed antimicrobial activities against Aspergillus niger and Candida albicans only but not against the tested bacteria.
Journal of the Serbian Chemical Society. 01/2008;
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ABSTRACT: The effects of vibration intensity, superficial gas velocity and content of solid particles on the volumetric oxygen mass transfer coefficient (k1a) in a 16.6 cm i.d. multiphase reciprocating plate column were strudied. The k1a increased with increasing vibration intensity and superficial gas velocity, and decreased with increasing content of solid particles. The k1a was correlated with the specific time-averaged power consumtion, the superficial gas velocity, the column diameter and the content of solid particles.
Journal of the Serbian Chemical Society. 01/2007;
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ABSTRACT: Flavonoids were analysed in the extracts of garden (Salvia officinalis L.) and glutinous (Salvia glutinosa L.) sage. Ultrasonic extraction (20 minutes at 40 °C) and classical maceration (6 h at room temperature) of the extractable substances from dried herbs and dried residual plant materials from which the essential oil had previously been removed by hydrodistillation were performed with petroleum ether, 70 % aqueous solution of ethanol and water. It was found that the extracts from both plants contained flavonoids, but their compositions were dependent of the plant species, the polarity of the extracting solvent and the extraction technique applied. Apigenin and its derivatives (e.g., apigenin 4'-methyl ether), scutellarein 6-methyl ether, isoscutellarein 8-methyl ether, luteolin and 6-OH-luteolin-6-methyl ether where distinctive for S. officinalis. Apigenin, luteolin, 6-OH-luteolin-6-methyl ether, kaempherol 3-methyl ether, kaempherol 3,7-dimethyl ether, quercetin 3,7,3'-trimethyl ether and quercetin 3,7,3',4'-tetramethyl ether were distinctive for S. glutinosa. The flavonoids were also detected in considerable quantities in the plant material from which the essential oils had been already removed. Hence, this industrial waste plant material might be further used as a source of the flavonoids.
Journal of the Serbian Chemical Society. 01/2007;
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ABSTRACT: The influence of the geometry of a reciprocating plate column (diameter), superficial gas velocity, vibration intensity and content of the solid phase in the column on the gas hold-up in a three phase column (G–L–S) were investigated in this study. For comparison, the gas hold-up was also analyzed in a gas–liquid system (G–L) in the same type of column. Good agreement between the experimentally determined values of the gas hold-up and those calculated on the basis of the derived correlation for the G–L and G–L–S system was obtained.
Journal of the Serbian Chemical Society. 01/2005;
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ABSTRACT: The influence of the gas flow rate and vibration intensity in the presence of the solid phase (polypropylene spheres) on axial mixing of the liquid phase in a three phase (gas-liquid-solid) Karr reciprocating plate column (RPC) was investigated. Assuming that the dispersion model of liquid flow could be used for the real situation inside the column, the dispersion coefficient of the liquid phase was determined as a function of different operating parameters. For a two-phase liquid-solid RPC the following correlation was derived: DL = 1.26(Af)1.42 UL0.51 eS0.23 and a similar equation could be applied with ± 30 % confidence for the calculation of axial dispersion in the case of a three-phase RPC: DL = 1.30(Af)0.47 UL0.42 UG0.03eS-0.23.
Journal of the Serbian Chemical Society. 01/2004;
