Cevdet Demir

Phenolic Content and Antioxidant Activity of Raspberry and Blackberry Cultivars

Raspberry (Aksu Kirmizisi, Rubin, Newburgh, Hollanda Boduru, Heritage) and blackberry (Bursa 1, Bursa 2, Jumbo, Chester) cultivars were assayed for antioxidant activity (determined as 2,2-azino-di-[3-ethylbenzothialozine-sulphonic acid][ABTS], 2,2-diphenyl-1-picrylhydrazyl radical [DPPH], and cupric ion reducing antioxidant capacity [CUPRAC]), total phenol, total flavonoid, and total anthocyanin contents. In addition, 10 anthocyanins and anthocyanidins were determined in raspberry and blackberry by liquid chromatography-mass spectrometry (LC-MS/MS). Raspberry and blackberry had the highest ABTS, DPPH, CUPRAC, total phenol, and total flavonoid contents in methanol extracts, whereas total anthocyanin contents were the highest in water extracts. The antioxidant activity of the raspberry and blackberry was directly related to the total amount of phenolic compounds detected in the raspberry and blackberry. All antioxidant activity values were highly correlated with anthocyanin content in blackberry (0.93 < or = r < or = 0.99, P = 0.05). On the other hand, high correlation between total flavonoid content and antioxidant activity was recorded in water extract of blackberry (0.91 < or = r < or = 0.93, P = 0.05). ABTS value was highly correlated with total flavonoid content in methanol extract (r = 0.90), whereas total flavonoid content was relatively less correlated with DPPH (r = 0.85) and CUPRAC (r = 0.89).

Cold vapour generation and on-line trapping of cadmium species on quartz surface prior to detection by atomic absorption spectrometry

A quartz trap for on-line preconcentration of Cd species was designed. The cold vapour generation technique was used for the generation of Cd species. The trapping medium was formed by external heating of the inlet arm of a quartz T-tube. The generated analyte species were trapped on a quartz surface heated to the collection temperature, 350 °C, and the collected species were revolatilized when the trap was heated further to revolatilization temperature, 1000 °C, and hydrogen gas was introduced in the trapping medium. Two-level fractional factorial design and central composite design were used to optimize generation conditions in the flow injection mode. The results of the fractional factorial design demonstrated that the factors and their interactions were statistically significant. Three factors, length of reaction coil, carrier HCl concentration and NaBH4 concentration, were considered to be the most significant parameters in the optimization and their optimum values were found to be 30 cm, 0.3 M and 3% (m/v), respectively. Sea-water (BCR), tomato leaves (NIST 1573a) and oyster tissue (NIST 1566b) standard reference materials were analyzed to assess the accuracy of the proposed method. For a collection period of 3.0 min, i.e., 6.0 ml sample volume, the 3σ limit of detection was 1.8 pg ml−1; the enhancement factor for LOD was found to be 90 as compared with FI-HGAAS. The sample throughput rate was 12 h−1.

Determination of phenolic compounds in Prunella L. by liquid chromatography-diode array detection.

Four species of Prunella L. (Prunella vulgaris L., Prunella laciniata L., Prunella grandiflora L. and Prunella orientalis Bornm.) belong to the family of Lamiaceae and representing popular Western and Chinese herbal medicine were examined for the content of phenolic compounds. Phenolic acids (rosmarinic acid, caffeic acid, ferulic acid, chlorogenic acid, protocatechuic acid), flavonoids (rutin, quercetin) in different quantitative proportions depending on extracts were determined by the rapid, selective and accurate method combining solvent/acid hydrolysis extraction and high performance liquid chromatography-diode array detection (HPLC-DAD). Water, methanol, butanol, acetonitrile, ethyl acetate, hexane and their acidic solutions were used to examine the efficiency of different solvent systems for the extraction of phenolic compounds. Acid hydrolysis extraction was established as the most suitable extraction method for phenolic compounds.

Principal component analysis and cluster analysis for the characterisation of marbles by capillary electrophoresis.

Chemical characterisation has been carried out on 25 quarry marbles collected from Marmara, Aegean and Thrace regions of Turkey. Ten elements were determined by capillary electrophoresis (CE). Principal component analysis and cluster analysis techniques were utilised to define grouping of different marble samples. These techniques showed that the analysed marbles were differentiable mainly by provenance. Experimental conditions such as pH, applied voltage and concentration of alpha-hydroxyisobutyric acid (HIBA) were optimised to achieve the best separation of metal ions using central composite design. The optimum pH 3.7, applied voltage 15kV and concentration of HIBA 10mM were found to provide the best separation for all metal ions investigated.

Determination of total phenolic content in Prunella L. by horseradish peroxidase immobilized onto chitosan beads

Horseradish Peroxidase (HRP) was immobilized by covalent binding onto glutaraldehyde cross-linked chitosan beads and these beads were used for determination of total phenolic content in Prunella L. species. Central composite design (CCD) was employed to optimize the conditions for the maximum HRP activity and to understand the significance and interaction of the factors affecting the activity of immobilized HRP. The results indicated that enzyme concentration and immobilization time were significant factors for the immobilization of HRP. The optimum conditions were determined as enzyme concentration 0.25 mg mL−1, pH 8.0 and immobilization time 20h. The recovered activity was obtained as 81% after immobilization under optimal conditions. Total phenol content was determined in four Prunella L. species (Prunella vulgaris L., Prunella laciniata (L.) L., Prunella orientalis Bornm., Prunella grandiflora L.) extracted using methanol, water and methanol/water (4 : 1, v/v). The enzymatic method is based on the spectrophometric measurement of the final quinone-imine colored product, absorbing at 510 nm, by HRP oxidation in presence of hydrogen peroxide. The results were compared with those obtained by applying the Folin method. The highest total phenol content was obtained with the methanol/water (4 : 1, v/v) extract of Prunella vulgaris L. by immobilized HRP method (63.75 mg gallic acid equivalent (GAE) per g dried plant). Operational stability was determined with immobilized HRP and it indicated that a small enzyme deactivation (15%) occurred after 10 consecutive uses.

Orthogonal signal correction‐based prediction of total antioxidant activity using partial least squares regression from chromatograms

The multivariate calibration methods—partial least squares (PLS), orthogonal signal correction and partial least squares (OSC‐PLS)—were employed for the prediction of total antioxidant activities of four Prunella L. species. High‐performance liquid chromatography (HPLC) and spectrophotometric approaches were used to determine the total antioxidant activity of the Prunella L. samples. Several preprocessing techniques such as smoothing and normalization were employed to extract the chemically relevant information from the data after alignment with correlation optimized warping. The importance of the preprocessing was investigated by calculating the root mean square error for the calibration set for the total antioxidant activity of Prunella L. samples. The models developed on the basis of the preprocessed data were able to predict the total antioxidant activity with a precision comparable to that of the reference 2,2‐azino‐di‐(3‐ethylbenzothialozine‐sulfonic acid) and 2,2‐diphenyl‐1‐picrylhydrazyl methods. The OSC‐PLS model seems preferable because of its predictive and describing abilities and good interpretability of the contribution of compounds to the total antioxidant activity. The contribution of individual phenolic compounds to the total antioxidant activity was identified by HPLC. Copyright

Response Surface Optimized Ultrasonic-Assisted Extraction of Quercetin and Isolation of Phenolic Compounds From Hypericum perforatum L. by Column Chromatography

The effects of ultrasonic-assisted extraction factors for the main phenolic compound (quercetin) from Hypericum perforatum L. were optimized using the Box–Behnken design (BBD) combined with response surface methodology. The BBD was employed to evaluate the effects of extraction temperature (30–70°C), extraction time (20–80 min), methanol concentration (20–80%, v/v), and HCl concentration (0.8–2.0 M) on the content of one of the major phenolic compounds of quercetin. The extracts were analyzed by high performance liquid chromatography (HPLC). The major phenolic compounds of H. perforatum were isolated and the antioxidant capacity and total phenol content were determined in crude extract and fractions. The optimum conditions were determined as extraction temperature 67°C, extraction time 67 min, methanol concentration 77% (v/v), and HCl concentration 1.2 M. The predicted content of quercetin was 10.81 mg/g dried plant under the optimal conditions and the subsequent verification experiment with 11.09 mg/g dried plant confirmed the validity of the predicted model. The isolated compounds were identified as quercetin, cyanidin, protocatechuic acid, and kaempferol.

Methods for Lipase Immobilization and Their Use for Biodiesel Production from Vegetable Oil

In the present work, two different lipases (triacylglycerol hydrolase, EC 3.1.1.3), Lipozyme TL–100L and Novozyme 388, were immobilized onto three different low-cost supports using both adsorption and covalent method: celite 545, silica gel, and styrene-divinylbenzene copolymer. The maximum immobilization yield was obtained as 79.0% for Lipozyme TL–100L and the highest specific activity was 6.5 U/mg protein for Novozym 388. The properties of the support and immobilized derivatives were characterized by Fourier transform infrared spectroscopy. Maximum methyl esters yield was obtained as 98.3%. The lipases, which are immobilized by covalently, proved to be stable after even 10 repeated reuses.

Prediction of Total Phenolic Content in Extracts of Prunella Species from HPLC Profiles by Multivariate Calibration

The multivariate calibration methods—principal component regression (PCR) and partial least squares (PLSs)—were employed for the prediction of total phenol contents of four Prunella species. High performance liquid chromatography (HPLC) and spectrophotometric approaches were used to determine the total phenol content of the Prunella samples. Several preprocessing techniques such as smoothing, normalization, and column centering were employed to extract the chemically relevant information from the data after alignment with correlation optimized warping (COW). The importance of the preprocessing was investigated by calculating the root mean square error (RMSE) for the calibration set of the total phenol content of Prunella samples. The models developed based on the preprocessed data were able to predict the total phenol content with a precision comparable to that of the reference of the Folin-Ciocalteu method. PLS model seems preferable, because of its predictive and describing abilities and good interpretability of the contribution of compounds to the total phenol content. Multivariate calibration methods were constructed to model the total phenol content of the Prunella samples from the HPLC profiles and indicate peaks responsible for the total phenol content successfully.

Quantification of DNA damage products by gas chromatography tandem mass spectrometry in lung cell lines and prevention effect of thyme antioxidants on oxidative induced DNA damage

Lung cancer has a high treatment cost and poor prognosis in comparison to other types of cancers. This work was involved in studying oxidative DNA base damage inhibition. Accordingly, standard carvacrol, thymol, thymoquinone with water and water-methanol extract of thyme (Origanum vulgare L. subsp. hirtum (link.) Ietswaart), thyme oil and thyme water were prepared and investigated for their efficacy to inhibit DNA oxidative damage formed by H2O2 in malignant lung cells (A549). The antioxidant capacity by ABTS assay was 271.73 ± 11.45 mg trolox equivalent/mL for thyme oil. HPLC analysis was carried out to determine the contents of different thyme extracts, results showing the presence of carvacrol, thymol, protocatechuic acid, caffeic acid, epicatechin and rosmarinic acid in water and water-methanol extracts while only carvacrol and thymol were found in thyme oil and thyme water. After DNA isolation from the cultured cells, the formed oxidative induced DNA damage products were analysed using GC-MS/MS. It was proven that the antioxidants in the cell culture media have succeeded to inhibit oxidative DNA base damage. Thymoquinone was shown to be the best protectant antioxidant among other antioxidants against the formation of oxidative DNA damage, whereas water-methanol extract of thyme was the best among the plant-sourced samples. Thymoquinone and thyme water-methanol extract were investigated for their efficacy on cultured healthy lung cells (BEAS-2B), and it was proven that they are efficient in protection against the oxidation of DNA of healthy lung cells too.