Serhat Keser

Synthesis and characterization of Ce-substituted hydroxyapatite by sol-gel method.

Both undoped hydroxyapatite (HAp) and three Ce-substituted HAp samples with variable amounts (from 0.5 to 2 at.%) of Ce were synthesized by sol-gel method. The samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy to determine the crystallite size, crystallinity degree, phases, functional groups, morphology and elemental composition. In all samples, the amount of HAp exceeded 92%, while the amount of admixture β-TCP was always below 8% and no changes were observed by addition of Ce. The crystallinity degree of the samples was always within 84-89%, while the calculated dimensions of crystallites appeared to be within 26-35nm. The microstructure and elemental composition of all the samples were found to be affected by the addition of Ce.

Strontium substituted hydroxyapatites: Synthesis and determination of their structural properties, in vitro and in vivo performance.

The objective of this study is to present a detailed report related to the synthesis and characterization of strontium substituted hydroxyapatites. Based on this purpose, hydroxyapatite (HAp) bioceramics with different amounts of strontium (e.g., 0, 0.45, 0.90, 1.35, 1.80 and 2.25 at.%) were prepared using a sol-gel method. The effects of Sr substitution on the structural properties and biocompatibility of the samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques, in vitro and in vivo tests. All the samples composed of the nanoparticles ranging from 21 to 27 nm. The presence of Sr at low levels influenced the crystal size, crystallinity degree, lattice parameters and volume of the unit cell of the HAp. Both in vitro conditions and soaking period in simulated body fluid (SBF) significantly affected these properties. Especially, the (Ca+Sr)/P molar ratio gradually decreases with increasing soaking period in SBF. Animal experiments revealed the bone formation and osseointegration for all samples, and as compared with other groups, more reasonable, were observed for the sample with the lowest Sr content.

Resveratrol (trans-3,4′,5-trihydroxystilbene) decreases lipid peroxidation level and protects antioxidant capacity in sera and erythrocytes of old female Wistar rats induced by the kidney carcinogen potassium bromate

Resveratrol is a natural polyphenolic compound and it is found in number of edible plants, especially grapes and peanuts, has been shown to have anti-inflammatory, anti-oxidant, anti-tumor and anti-platelet activities. The aim of the study was to examine the effects of resveratrol on the level of malondialdehyde (MDA), homocysteine, cholesterol, GSH, GSSG and lipophylic vitamins in serum and erythrocytes of old female Wistar rats induced by the kidney carcinogen potassium bromate (KBrO(3)). In the study, total 30-old female Wistar rats were used, and the rats were randomly divided into three groups. The first group was used as a control, the second group KBrO(3) group, and third group R+KBrO(3). Rats in KBrO(3) and R+KBrO(3) groups were injected intraperitoneally a single dose KBrO(3) (80mg/kg) in physiologic saline buffer. After 2days, those in R+KBrO(3) group were intraperitoneally injected with resveratrol (33mg/kg) four times per week, and physiological saline was injected to control group rats. All the analysis was performed fully automatic with high performance liquid chromatography equipment. The results indicate that serum cholesterol level in the R+KBrO(3) group was higher than the control group (p<0.05), and level of the cholesterol in erythrocytes membranes was lower in the same group (p<0.01). The MDA level in serum and erythrocytes of the R+KBrO(3) were lower than the control and KBrO(3) groups (p<0.01). However, the MDA level in erythrocytes of the KBrO(3) group was high compared to the control group (p<0.05). Homocysteine and δ-tocopherol levels in serum of the R+KBrO(3) group were lower than the control group (p<0.05, p<0.001). α-Tocopherol level in serum and erythrocytes of the KBrO(3) group was lower than the control group (p<0.05), whereas its level was not found to differ between the control and R+KBrO(3) groups. GSH and GSSG levels in the KBrO(3) group of erythrocytes were higher than control group (p<0.05, p<0.01), however the ratio GSH/GSSG in the same group was lower than control group. In conclusion, our results confirm that the lipid peroxidation formation in serum and erythrocytes of old female Wistar rats by induced the KBrO(3) is prevented by the resveratrol. It was observed that the antioxidant capacity of erythrocytes was protected by resveratrol.

Total phenolic contents and free-radical scavenging activities of grape (Vitis vinifera L.) and grape products

Grape is one of the worlds largest fruit crops, with an approximate annual production of 58 million metric tons, and it is well known that the grape skins, seeds and stems, waste products generated during wine and grape juice processing, are rich sources of polyphenols. It contains flavonoids, phenolic acids and stilbenes. In this study, we tried to determine antioxidant properties and phenolic contents of grape and grape products (fresh fruit, seed, dried fruit, molasses, pestil, vinegar) of ethanol and water extracts. Antioxidant properties of extracts were investigated by DPPH√, ABTS√+, superoxide, H2O2 scavenging, reducing power, metal chelating activity and determination of total phenolic contents. The seed extracts revealed highest ABTS√+, DPPH√, H2O2 scavenging and reducing power activities. Furthermore, these extracts showed higher total phenolic contents than other grape product extracts.

In vitro characterization of polyvinyl alcohol assisted hydroxyapatite derived by sol-gel method.

The synthesis and characterization of sol-gel derived hydroxyapatite (HAp) were investigated with the effects of the addition of polyvinyl alcohol (PVA) to the structural and material in vitro behavior. All samples were soaked in simulated body fluid (SBF) for 14 and 28 days. The characterization of bioceramics before and after immersing in SBF was carried out by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis (DTA), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques. After the simulated body fluid period, the crystal structure and phase of HAp samples did not change significantly. The characteristic bands of hydroxyl, phosphate and carbonate groups were detected. HAp exhibited a thermal stability of room temperature to 1000 °C. The surface morphologies of the samples show an evident change with the soaking period in SBF.

Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications

The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA.

Structural and dielectric properties of yttrium-substituted hydroxyapatites.

Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content.

The investigation of some bioactive compounds and antioxidant properties of hawthorn (Crataegus monogyna subsp. monogyna Jacq).

Aim: The antioxidant and pharmacological effects of hawthorn have mainly been attributed to the polyphenolic contents. The aim of this research is to determine some bioactive compounds and antioxidant properties of hawthorn aqueous and ethanol extracts of leaves, flowers, and ripened fruits. Materials and Methods: For this purpose, antioxidant activities of extracts were assessed on DPPH•, ABTS•+, superoxide scavenging, reducing power and ferrous metal chelating activity assays and phenolic content of extracts was determined by Folin—Cioacalteu’s reagent. Results: The flavonoids including rutin, apigenin, myricetin, quercetin, naringenin and kaempferol, were identified by high-performance liquid chromatography in the hawthorn extract. Conclusion: It was observed the aqueous and ethanol extracts of Crataegus monogyna subsp. monogyna fruits showed the highest activity in reducing power and metal chelating activity assays. In addition, it was determined that the aqueous flower extract showed higher flavonoid content than aqueous leaves extract. The antioxidant and pharmacological effects of hawthorn have mainly been attributed to the polyphenolic contents.

Antiradical activities and phytochemical compounds of firethorn (Pyracantha coccinea) fruit extracts

Firethorn fruits have been used in traditional medicine owing to their diuretic, cardiac and tonic properties. In this study, the antiradical activities and phenolic, phytosterol, lipid-soluble vitamin and fatty acid contents of firethorn fruits were investigated. Antiradical activities of firethorn extracts (ethanol, water, methanol, acetone and diethyl ether) were determined by using DPPH√, ABTS√+ and OH√ radical-scavenging assays. The scavenging activity of the firethorn ethanol, methanol and acetone extracts on ABTS is higher than BHT. The scavenging activity of the firethorn methanol and ethanol extracts on DPPH is higher than BHT. δ-Tocopherol, α-tocopherol, vitamin K, vitamin D, β-sitosterol, ergosterol, stigmasterol, and the major fatty acids linolenic acid and palmitic acid were determined in firethorn. These results indicate that firethorn can be a good source of natural antioxidant owing to the presence of fatty acids, vitamins, phytosterols and phenolic compounds, and antiradical properties. Moreover, this study is the first report about antiradical and phytochemical properties of Pyracantha coccinea fruit extracts.

Phytochemical Compounds and Biological Activities of Celtis tournefortii Fruits

Abstract It is known that Celtis species have been used in healing wound, epilepsy crisis, and stomach pain among the people. The antiradical (DPPH, OH, ABTS) activities, phytochemical compounds (total proanthocyanidin, total flavonoid, total phenolic, flavonoids, phenolic acids, sterols, lipid soluble vitamins, fatty acids), antimicrobial, antiproliferative (MCF-7, HCT-116, A2780, PC-3) activities of water, ethanol, methanol extracts of C. tournefortii fruits were evaluated in this study. All the C. tournefortii fruit water extracts were higher scavenged OH radical than standard antioxidant BHT. It was detected that C. tournefortii includes high amount of α-tocopherol (2.65 mg/kg), vitamin D (10.05 mg/kg), ergosterol (78.70 mg/kg), stigmasterol (185.90 mg/kg), unsaturated fatty acids (74.47%). C. tournefortii extracts showed antiproliferative activity on MCF-7, HCT-116, A2780, PC-3 cancer cell lines and antimicrobial activity on some microorganisms when compared to standard antibiotics. Also, this study is the first report about phytochemical contents, antiproliferative, antimicrobial, antiradical properties of C. tournefortii fruits.