Murat Küçük

Does caffeine bind to metal ions

Abstract The complex formation capacity of caffeine, a highly-consumed tea and coffee component, was determined for Ca, Mg, Fe, Zn, Pb, Mn, Co and Cr metal ions. The binding constants of metal ion–caffeine complexes for the metals chosen were determined spectrophotometrically. The results were compared with the known stability constants of metal ion–EDTA complexes, EDTA being known for its high metal binding capacity. Furthermore, iron chelating activity of caffeine, using the ferrozine reference method, was studied and compared with that of EDTA. The results showed very little complex formation capacity of caffeine with binding constants of 29.6, 22.4, 59, 396, 55, 9.3, 83 and 592 M −1 for Ca, Mg, Fe, Zn, Pb, Mn, Co and Cr metal ions, respectively, in contrast to that of EDTA. The iron chelating activity of caffeine was also found to be 6%, which was considered to be quite low compared with EDTA.

Chemical Composition and Antimicrobial Activities of the Essential Oils of Teucrium chamaedrys. subsp. chamaedrys., T. orientale. var. puberulens., and T. chamaedrys. subsp. lydium.

Abstract The composition of the essential oils obtained from the air-dried Teucrium chamaedrys. L. subsp. chamaedrys., Teucrium orientale. L. var. puberulens., and Teucrium chamaedrys. L. subsp. lydium. (Lamiaceae) were analyzed by GC-MS. Thirty-six, 35, and 33 components were identified in the essential oils, and germacrene D (16.7%) was the most abundant constituent in T. chamaedrys. subsp. chamaedrys., and β-caryophyllene was the most abundant component in both T. orientale. var. puberulens. and T. chamaedrys. subsp. lydium. in the ratios 21.7% and 19.7%, respectively. The isolated essential oils of the plants were tested for antimicrobial activity and showed moderate antibacterial activity against Gram-positive and Gram-negative bacteria, but no antifungal activity was observed against two yeast-like fungi.

New thiophene-1,2,4-triazole-5(3)-ones: highly bioactive thiosemicarbazides, structures of Schiff bases and triazole-thiols.

Key compound 2-(4-amino-5-oxo-3-(thiophene-2-ylmethyl)-4,5-dihydro-1,2,4-tiazole-1-yl) acetohydrazide (3) was synthesized by reacting hydrazine hydrate with ethyl-2-(4-amino-5-oxo-3-(thiophene-2-ylmethyl)-4,5-dihydro-1,2,4-tiazole-1yl)acetate (2), obtained in basic media from 4-amino-5-(thiophene-2-ylmethyl)-2H-1,2,4-triazole-3(4H)-one (1). Compound 3 was converted to thiosemicarbazide derivatives (4a-d) and Schiff base derivatives 6a-e and 7a-e. The treatment of compound 4 with NaOH gave 4-amino-2-((4-(4-aryl)-5-mercapto-4H-1,2,4-triazole-3-yl)methyl)-5-(thiophene-2-ylmethyl)-2H-1,2,4-triazole-3(4H)-ones (5a-d). All newly compounds, well characterized by elemental analyses, IR, (1)H NMR, (13)C NMR and mass spectral studies were tested for their antioxidant and antimicrobial activities. Thiosemicarbazide derivatives (4a-d) were highly active in two antioxidant tests with 69.0-88.2% DPPH· scavenging and 503-1257 μM TEAC values, while the others showed lower or no activity. The results of the two antioxidant tests correlated well. Moreover, Thiosemicarbazide derivatives (4a-d) also showed antibacterial activity against Staphylococcus aureus, Bacillus cereus, and Mycobacterium smegmatis. Thiosemicarbazide group deserves attention in the synthesis of bioactive compounds.

Synthesis of new 1,2,4-triazole compounds containing Schiff and Mannich bases (morpholine) with antioxidant and antimicrobial activities

Abstract Compound 2 was synthesized by reacting CS2/KOH with compound 1. The treatment of compound 2 with hydrazine hydrate produced compound 3. Then, compound 3 was converted to Schiff bases (4a–d) by the handling with several aromatic aldehydes. The treatment of triazole compounds 4a–d containing Schiff base with morpholine gave compounds 5a–d. All compounds were tested for their antioxidant and antimicrobial activities. The antioxidant test results of DPPH• radical scavenging and ferric reducing/antioxidant power methods showed good antioxidant activity. The triazole-thiol (3) was the most active, and the effect of the substituent type of the thiophene ring on the activity was same for both Schiff bases (4a–d) and Mannich bases (5a–d). Among the newly synthesized triazole derivatives, the Schiff base 4d and the Mannich base 5d carrying nitro substituent on the thiophene ring showed promising antibacterial and antifungal activity, with lower MIC values than the standard antibacterial ampicillin.

Stereoselective photochemistry of substituted chalcones in solution and their antioxidant activities

Three new δ-truxinic type cyclobutanes [(1β,2α)-di-(4-ethylbenzoyl)-(3β,4α)-di-(4-methoxyphenyl) cyclo butane (4), (1β,2α)-di-(4-nitrobenzoyl)-(3β,4α)-di-(4-ethylphenyl) cyclobutane (5), and (1β,2α)-di-(4-ethylbenzoyl)-(3β,4α)-di-(4-ethylphenyl) cyclobutane (6)] have been prepared by stereoselective photodimerisation of the corresponding chalcone monomers (1-3) in solution. NMR and MS of the dimers are discussed. The precursor chalcones and the dimeric products showed antioxidant activities to different extents with respect to the individual compounds as well as to the antioxidant methods used.

Synthesis and Anticancer Evaluation of Some New 4-Amino-3- (p-methoxybenzyl)-4,5-dihydro-1,2,4-triazole-5-one Derivatives

Abstract 4-Amino-3-p-methoxybenzyl-5-oxo-4,5-dihydro-1,2,4-triazol-1-yl-acetic acid ethyl ester (2) was prepared from 4-amino-4,5-dihydro-1H-1,2,4-triazole-5-one (1) and ethyl bromoacetate. Compound 3 was synthesized by the condensation of 2 with hydrazine hydrate. The treatment of compound 3 with various aromatic aldehydes resulted in the formation of arylidene hydrazides as cistrans conformers 4a - g. Thiosemicarbazide derivative 5 was prepared by the reaction of compound 3 with phenylisothiocyanate. Cyclization of 5 with sodium hydroxide resulted in the formation of compound 6. Treatment of 6 with benzyl bromide gave compound 7. Four of the newly synthesized compounds were screened for their anticancer activity against a panel of 60 cell lines derived from nine cancer types, namely, non-small cell lung, colon, breast, ovarian, leukemia, renal, melanoma, prostate and CNS cancers at a fixed dose of 10 μM.

A new colorimetric DPPH• scavenging activity method with no need for a spectrophotometer applied on synthetic and natural antioxidants and medicinal herbs

Abstract 2,2-Diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging, the most commonly used antioxidant method with more than seventeen thousand articles cited, is very practical; however, as with most assays, it has the major disadvantage of dependence on a spectrophotometer. To overcome this drawback, the colorimetric determination of the antioxidant activity using a scanner and freely available Image J software was developed. In this new method, the mixtures of solutions of DPPH• and standard antioxidants or extracts of common medicinal herbs were dropped onto TLC plates, after an incubation period. The spot images were evaluated with Image J software to determine CSC50 values, the sample concentrations providing 50% colour reduction, which were very similar with the SC50 values obtained with spectrophotometric method. The advantages of the new method are the use of lower amounts of reagents and solvents, no need for costly spectrophotometers, and thus significantly lowered costs, and convenient implementation in any environment and situation.

An investigation of frequently consumed edible oils in Turkey in terms of omega fatty acids

The fatty acid profiles of frequently consumed oils and crops cultivated in Turkey were investigated in regard to omega fatty acids. Analyses were carried out on commercially sold oils, sunflower, olive, and fish oils, and oils extracted from fatty seeds of hazelnut, walnut, olive, sunflower, poppy, sesame, and pumpkin, and butter produced in Turkey. Hazelnut and olive oils were found to be rich in omega-9 (oleic acid 18:1), walnut, poppy seed, sesame, and pumpkin seed were rich in omega-6 (linoleic acid 18:2), and butter was rich in short chain fatty acids and omega-9. Fish oil, from mackerel, was the richest in omega-3 fatty acids and fatty acid diversity. There were some alterations between commercially sold oils and oils extracted from seeds in regard to fatty acid percentages and variety.

Microwave-assisted synthesis of 4'-azaflavones and their N-alkyl derivatives with biological activities.

4′‐Azaflavone (=2‐(pyridin‐4‐yl)‐4H‐1‐benzopyran‐4‐one; 4) and 3‐[(pyridin‐4‐yl)methyl]‐4′‐azaflavone (5) were synthesized by a simple environmentally friendly microwave‐assisted one‐pot method through the cyclization of 3‐hydroxy‐1‐(2‐hydroxyphenyl)‐3‐(pyridin‐4‐yl)propan‐1‐one (1), (E)‐2′‐hydroxy‐4‐azachalcone (2; chalcone=1,3‐diphenylprop‐2‐en‐1‐one), and 2′‐hydroxy‐2‐[(hydroxy)(pyridin‐4‐yl)methyl]‐4″‐azachalcone (3) under solventless conditions using silica‐supported NaHSO4, followed by treatment with base. In addition, N‐alkyl‐substituted 4′‐azaflavonium bromides 6 and 7 were prepared from compounds 4 and 5, respectively. The antimicrobial and antioxidant activities of compounds 1–7 were tested. The N‐alkyl‐substituted 4′‐azaflavonium bromides 6 and 7 showed high antimicrobial activity against the Gram‐positive bacteria and the fungus tested, with MIC values close to those of reference antimicrobials ampicilline and fluconazole. The alkylated compounds 6 and 7 also showed a good antioxidant character in the two antioxidant methods, DPPH (=1,1‐diphenyl‐2‐picrylhydrazyl) radical‐scavenging and ferric reducing/antioxidant power (FRAP) tests.

In vitro effects of peroxynitrite treatment on fish liver catalase activity.

The effect of peroxynitrite (PN), a highly toxic agent, on catalase (CAT) activity in fish liver microsomal homogenates was determined. PN was synthesized by mixing acidic hydrogen peroxide solution with sodium nitrite solution and then adding sodium hydroxide solution into the mixture in order to stabilize the highly labile compound peroxynitrous acid (ONOOH) in peroxynitrite anion form (ONOO− ). The effect of PN and decomposed peroxynitrite (DPN), prepared by preincubation with HCl, was monitored by using a constant amount of homogenate containing the CAT enzyme. Significant losses were observed in the CAT activity of fish liver enzyme after treatment with PN and also with DPN products, the inhibitory effect of PN being slightly more pronounced than that of DPN. IC50 values were 5.5 and 8.5 μM for PN and DPN, respectively. The PN inhibition of CAT activity is due to both the effects of the secondary and decomposition products of PN and its nitration and oxidation effects on the amino acid residues of the enzyme.