Browsing by Subject "Chromatography, High Pressure Liquid"
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Item Ground red peppers: Capsaicinoids content, scoville scores, and discrimination by an electronic nose(2002) Korel F.; Baǧdatlioǧlu N.; Balaban M.Ö.; Hişil Y.High-pressure liquid chromatography (HPLC) was used to determine the capsaicin, dihydrocapsaicin, and total capsaicinoids levels of different ground red pepper samples obtained from local retail markets in Izmir, Turkey. Scoville scores were determined using sensory tests. An electronic nose (EN) was used to discriminate ground red pepper samples by headspace volatiles. EN data were analyzed using discriminant function analysis (DFA). An overall correct classification rate of pepper varieties by EN of 91% was obtained. A linear correlation between capsaicin, dihydrocapsaicin, and total capsaicinoids and Scoville scores was also observed, and R2 values of 0.89, 0.85, and 0.91 were obtained, respectively.Item Determination of the phytoalexin resveratrol (3,5,4′-Trihydroxystilbene) in peanuts and pistachios by High-Performance Liquid Chromatographic Diode Array (HPLC-DAD) and Gas Chromatography-Mass Spectrometry (GC-MS)(2005) Tokuşoǧlu Ö.; Ünal M.K.; Yemiş F.The phytoalexin resveratrol (3,5,4′-trihydroxystilbene) in edible peanut (Arachis hypogaea L.) and pistachio (Pistacia vera L.) varieties grown in Turkey was analyzed by high-performance liquid chromatographic diode array and gas chromatography-mass spectrometric detection. trans-Resveratrol in six peanut varieties, five pistachio varieties, and four market samples ranged between 0.03 and 1.92 μg/g. The Çerezlik 5025 peanut (1.92 ± 0.01 μg/g) and Ohadi pistachio genotype (1.67 ± 0.01 μg/g) had significantly higher trans-resveratrol contents. Peanuts contained 0.03-1.92 μg/g (av = 0.84 μg/g) of trans-resveratrol, whereas pistachio contained 0.09-1.67 μg/g (av = 1.15 μg/g). With exposure to UV light for 1 min, trans-resveratrol concentrations of samples ranged from 0.02 to 1.47 μg/g and those of cis-resveratrol from 0.008 to 0.32 μg/g. The occurrence of resveratrol in peanut and pistachio was confirmed by total ion chromatograms (TIC) of bis[trimethylsilyl]-trifluoroacetamide derivatives of resveratrol isomers and comparison of the mass spectral fragmentation data with those of a resveratrol standard. Formation of the cis-isomer in pistachios was higher than in peanuts. © 2005 American Chemical Society.Item Impact of renal function or folate status on altered plasma homocysteine levels in hypothyroidism(2006) Özmen B.; Özmen D.; Parildar Z.; Mutaf I.; Turgan N.; Bayindir O.Hyperhomocysteinemia is an independent risk factor for coronary, peripheral and cerebrovascular diseases. Moderately elevated total homocysteine (tHcy) levels have been reported in patients with overt hypothyroidism. Plasma tHcy concentration is affected by several physiological factors and is elevated under conditions of impaired folate and cobalamin status and in renal failure. The aim of this study was to assess plasma tHcy concentrations and to evaluate the role of potential determinants of plasma tHcy levels in hypothyroid patients. Fasting plasma tHcy, serum homocysteine-related vitamins folate and vitamin B12, serum cystatin C (CysC) and creatinine, were determined in 22 hypothyroid patients and compared with 25 healthy control subjects. Creatinine clearance (CCr) was calculated using the Cockroft-Gault formula. Plasma tHcy levels were determined by HPLC with fluorescence detection and serum CysC by automated particle enhanced immunoturbidimetry. Plasma tHcy, creatinine levels were significantly higher, and serum CysC levels, and creatinine clearance values were lower in hypothyroid patients than in control subjects. Folate levels were lower in hypothyroidic group compared to the control group. There were no differences in vitamin B12 levels between hypothyroid and control groups. Positive correlation was noted between tHcy and creatinine levels in hypothyroid patients (r = 0.596); however, an inverse correlation was found between tHcy and folate levels (r = -0.705) in hypothyroid patients. In conclusion, tHcy was increased in hypothyroidism, and this increase was more strongly associated with changes in serum folate than in serum creatinine and CysC, suggesting an altered folate status.Item Effect of yearly conditions and management practices on ochratoxin a production in sultana seedless vineyards(Taylor and Francis Ltd., 2012) Meyvaci K.B.; Aksoy U.; Eltem R.; Altindili A.; Akun T.; Takin E.Sun drying of seedless grapes (Vitis vinifera cv. Sultanina) is widely practised in the western Aegean Region providing Turkey with a significant share in the world trade of sultanas. Research was initiated in 1998 to determine the incidence of ochratoxin A (OTA), to identify the major factors resulting in contamination and to develop techniques to reduce or prevent contamination. This paper assesses OTA formation in five experimental vineyards located in Manisa province of Turkey between 1998 and 2003. The cultural practices recorded were tillage (type and timing), fertilisation, plant protection, irrigation, trellising, pruning, GA3 application, harvest maturity and date, and drying practices (type of drying yard, dipping into alkaline solution, length of drying period). In the experimental vineyards, no OTA was found at veraison. OTA levels in grapes harvested at fresh maturity ranged betweenItem Determination of vitamin e isomers of grape seeds by high-performance liquid chromatography-UV detection(2012) Şeker M.E.; Çelik A.; Dost K.A simple analytical method for the determination of vitamin E isomers in grape seeds by reversed-phase high-performance liquid chromatography with UV detection is described. The method is based on a solidliquid extraction separation on an ODS column, and the analytes are monitored at 295 nm with a UV detector. Tocopherols are extracted in n-hexane and directly injected onto the column without using any purification step, such as saponification, prior to the separation and determination. The chromatographic separation of tocopherols is achieved in 12 min with a mobile phase that consists of n-hexane and isopropyl alcohol (99.99:0.01, v/v). The method is reproducible and accurate, with respect to demonstrating a relative standard deviation between 2.57 and 3.30 (n=10, for 500 ng/mL) and a relative error between 0.84 and 6.54 (n=10, for 500 ng/mL), respectively. The theoretical limits are estimated as 25 ng/mL for α-tocopherol, 43 ng/mL for γ-tocopherol, and 83 ng/mL for δ-tocopherols. The method is then applied for the determination of tocopherols in grape seeds grown in Turkey. The amounts of tocopherols are calculated by using the standard addition method. © 2012 The Author.Item LC-MS/MS profiles and interrelationships between the enzyme inhibition activity, total phenolic content and antioxidant potential of Micromeria nervosa extracts(Elsevier Ltd, 2020) Sarikurkcu C.; Andrade J.C.; Ozer M.S.; de Lima Silva J.M.F.; Ceylan O.; de Sousa E.O.; Coutinho H.D.M.The objective of this study was to quantify the phenolic compounds and to evaluate and compare the biological activities of the ethyl acetate (EtOAc), methanolic (MeOH) and aqueous extracts from the Micromeria nervosa aerial parts, based on their antioxidant activity and enzymatic inhibition. Total phenolic and flavonoid contents were calculated and individual compo3unds were detected using LC-ESI-MS/MS. The antioxidant activity was determined using six different assays while enzymatic activity was determined by α-amylase and tyrosinase enzyme inhibition. The main phenolic constituents detected in the extracts were rosmarinic acid. In the antioxidant assays the aqueous extract was shown to be more efficient than the others. The EtOAc and MeOH extracts presented higher inhibitory activity with respect to α-amylase and tyrosinase. Regardless of the solvent, the results suggest M. nervosa aerial extracts present a biological potential due to their antioxidant activity and enzymatic inhibition. © 2020 Elsevier LtdItem Investigation of phenolic content in five different pine barks species grown in Turkey by HPLC-UV and LC-MS(Oxford University Press, 2021) Şeker M.E.; Çelik A.; Dost K.; Erdoğan A.Investigation of phenolic content from different pine bark species grown in Turkey was performed using a reversed-phase high pressure liquid chromatography with ultraviolet (RP-HPLC-UV) method. All phenolic constituents were separated in <26 min on reversed-phase C18 column with gradient mobile phase that consists of orthophosphoric acid, methanol and acetonitrile. Detections were made on an UV detector at 280 nm and at a flow rate of 1 mL/min. Samples were prepared according to Masqueller's conventional sample preparation method with slight modifications. To avoid the reduction in extraction efficiency the sample preparation step was carried out under argon atmosphere. The linearity of the method was between 0.9994 and 0.9999. The detection limits for the five phenolic constituents ranged from 0122 to 0.324 mg/L. Catechin and taxifolin were found in all pine barks at a concentration of 0.065 ± 0.002-1.454 ± 0.004 and 0.015 ± 0.001-23.164 ± 0.322 mg/g, respectively. Epicatechin was determined in four pine barks between 0.027 ± 0.001 and 0.076 ± 0.002 mg/g, ferulic acid in two pine barks between 0.010 ± 0.001 and 0.022 ± 0.001 mg/g and epicatechin gallate in only one of the pine barks at 0.025 ± 0.001 mg/g. Finally, the total amount of phenolic compounds and antioxidant capacities of the pine barks were found to be very high. © The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.comItem Simultaneous determination of six antibiotics belonging to four different classes in chicken meat BY HPLC/DAD and verification BY LC-MS/MS(Elsevier Ltd, 2023) Doyuk F.; Dost K.The hypothesis of this study was to develop an extraction method allowing side-by-side extraction of six antibiotics belonging to four different classes and an HPLC/DAD method for the determination of their residues in chicken breast meat. The validation data showed that this hypothesis was achieved. The results were then confirmed by LC-MS/MS method. Sample preparation was based on the classical solid–liquid extraction with methanolic citric acid. The average recoveries were satisfactory and ranged from 75.68 to 101.3%. The linearity of the developed HPLC/DAD method was very high in the concentration range studied (R2 > 0.9969). The accuracy and precision of the analytical method were between –10.8 and 12.0% relative error and 0.82 to 10.1% relative standard deviation, respectively. The LODs for five antibiotics ranged from 0.6 to 2.7 µg kg−1 and LOQs ranged from 2.0 to 8.9 µg kg−1. For penicillin G, the LOD was 0.16 and LOQ was 0.52 mg kg−1. © 2023 Elsevier Ltd