This paper describes carotenes extraction from carrot under different conditions involving different temperatures, treatment of samples, and solvents (ethanol, 2-propanol). Carrot roots (<I>Daucus carota</I> L. cv. Nevis F1) were tested for the extraction yields of carotenes at temperatures 20°C, 40°C, and 60°C, the samples having been examined after harvest, after cold storage (stored at 5°C), and after freezing (–18°C). In connection with the technology of the carotenoid concentrate production from carrots, it was found that the solubility and yield of carotene from carrot depend on the temperature and the time of extraction as well as the treatment of the sample. It was revealed that the best extraction efficiency was achieved with the samples treated by freezing and using the extraction 60°C for 2–4 hours. Higher temperatures caused an increase in the carotenoid concentrations. The carrot variety Nevis F1 and the extraction at 60°C were used for the model production of carotenoid concentrate.
Quercetin and rutin as well as catechin and epigallocatechin gallate were investigated, as widely distributed representatives of flavonols and flavanols, respectively, regarding their anti/pro-oxidant properties. The flavonoids are irreversibly oxidized at a dsDNA-modified screen-printed electrode within 0.368 to 0.449 V vs. SHE without binding to DNA. Using the DNA biosensor the detection scheme of a DNA prevention/degradation exploits the [Co(phen)(3)](3+) complex as an electrochemical DNA marker. Antioxidant activity of flavonoids was tested in a model cleavage mixture composed of 5 x 10(-7) mol L(-1) [Cu(phen)(2)](2+) as the catalyst, 1 x 10(-3) mol L(-1) ascorbic acid as the chemical reductant and atmospheric oxygen as the natural oxidant where reactive oxygen radicals are generated. The antioxidant activity increases with the concentration of flavonoids reaching a maximum where pro-oxidative behaviour becomes of importance. The pro-oxidant potency of flavonoids depends on the presence of atmospheric oxygen and follows the order quercetin>rutin>epigallocatechin gallate>catechin.
The antioxidative properties of aqueous plant extracts were evaluated using common methods such as the Rancimat and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) free radical method. Moreover, a voltammetric procedure based on the protective effect of antioxidants against the oxidative DNA damage was employed using a disposable DNA biosensor fabricated as a screen-printed electrode chemically modified by calf thymus double stranded (ds) DNA. The total polyphenols were also determined spectrophotometrically with the Folin-Ciocalteu agent. The extracts of oregano and lemon balm exhibited significantly higher activity than those of thyme and agrimony. The results were treated statistically and their operational character is discussed.
Data of adsorption isotherms of nitrogen adsorption at 77 K on various samples of zeolites were measured. Besides derivation of specific surface area by BET analysis, samples were characterised by values obtained by t-plots; specific surface areas of mesopores and specific volumes of micropores are also calculated. Results show the value of the use of t-plot method for the characterization of microporosity changes in zeolites after various treatments, and also for quantitative estimation of zeolite content in natural zeolites and the crystallinity of synthetic zeolites.
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