Sevgi Kolayli

Characterization and inhibition studies of an α-carbonic anhydrase from the endangered sturgeon species Acipenser gueldenstaedti.

An α-carbonic anhydrase (CA, EC 4.2.1.1) was purified and characterized kinetically from erythrocytes of the sturgeon Acipenser gueldenstaedti, an endangered species. The sturgeon enzyme (AgCA) showed kinetic parameters for the CO2 hydration reaction comparable with those of the human erythrocytes enzyme hCA II, being a highly active enzyme, whereas its esterase activity with 4-nitrophenyl acetate as substrate was lower. Sulphonamide inhibitors (acetazolamide, sulphanilamide) strongly inhibited AgCA, whereas metal ions (Ag+, Zn2+, Cu2+ and Co2+) were weak, millimolar inhibitors. Several widely used pesticides (2,4-dichlorophenol, dithiocarbamates, parathion and carbaryl) were also assayed as inhibitors of this enzyme. The dithiocarbamates were low micromolar AgCA inhibitors (IC50 of 16–18 µM), whereas the other pesticides inhibited the enzyme with IC50s in the range of 102–398 µM. The wide use of dithiocarbamate pesticides may be one of the factors enhancing the vulnerability of this sturgeon species to pollutants.

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.

A comparative study of antioxidant enzyme activities in freshwater and seawater-adapted rainbow trout

Comparative studies were performed on the antioxidant enzyme activities and thiobarbituric acid reactive substance (TBARS) concentration in liver and red cells of two groups of rainbow trout (Oncorhynchus mykiss). The fish of the first group were cultured in freshwater and the others were adapted to seawater by by being transferred from freshwater at 5–6 months of age. Catalase (CAT), glutathione peroxidase (GPX), and glutathione S‐transferase (GST) activities were significantly higher in hepatic and extrahepatic tissues in both of the fish groups. Superoxide dismutase (SOD) activities were found lower in the seawater‐adapted trout than in the freshwater‐cultured trout. In both tissues, TBARS were found significantly higher in the seawater‐adapted trout than in the freshwater trout. It was also observed that the red cells of the seawater‐adapted trout were much more resistant to oxidative stress than the red cells of the freshwater‐cultured trout. The results implicate that antioxidant capacities in the seawater‐adapted trout and freshwater trout may be related to physical and chemical characteristics of the environment.

Inhibition of mammalian carbonic anhydrases I-XIV with grayanotoxin III: solution and in silico studies

Abstract Grayanotoxin III (GTX3) was investigated for inhibition of all catalytically active mammalian carbonic anhydrase (CA, EC 4.2.1.1) isoforms, i.e. CA I to CA XIV. It showed micromolar inhibition (KIs of 8.01 and 6.13 µM) for cytosolic isoforms CA I and II, respectively. GTX3 showed a submicromolar inhibition (KIs in the range of 0.51–2.15 µM) for the remaining cytosolic (CA III, VII and XIII), membrane-associated/transmembrane (CA IV, IX, XII and XIV), mitochondrial (CA VA and CA VB) and secreted (CA VI) isoforms. This inhibition profile is very different from that of the sulfonamide CA inhibitors (CAIs), which possess different clinical applications. A molecular docking study for GTX3 within the active sites of CA I and II assisted to the understanding of molecular mechanism of the ligand. The interesting inhibition profile, coupled with various possibilities of interacting with the enzyme active site make this family of natural compounds attractive leads for designing novel chemotypes acting as CAIs.

Honey, polen, and propolis extracts show potent inhibitory activity against the zinc metalloenzyme carbonic anhydrase

Three different honey extracts from the endemic plant in the Black Sea region Rhododendron ponticum, were investigated for their inhibitory effects against the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1), more precisely the human (h) isoforms hCA I and hCA II. Hexane, methanol, ethanol, and water solid-phase extractions (SPEs) showed inhibitory activity towards the two CA isozymes which were related to the total phenolic content. The highest inhibitory effects (0.036–0.039 mg/mL) were those of propolis methanolic extract. Among the three different samples investigated here, the aqueous extracts showed lower inhibitory effects compred to the organic solvent SPE extracts (in the range of 1.150– 5.144 mg/mL). The studied honey extracts constitute an interesting source of phenolic derivatives that might serve to identify lead compounds, targeting the physiologically relevant enzymes CA I and CA II.

Comparative study of chemical and biochemical properties of different melon cultivars: standard, hybrid, and grafted melons.

Chemical and biochemical properties of standard, hybrid, and grafted melons cultivated under the same agricultural conditions in adjacent fields in the Cumra region of Turkey were investigated and compared based on pH, Brix, antioxidant activity, total phenolics, ascorbic acid, individual phenolics, sugar, and organic acid values. Seventeen different phenolic constituents were quantified by reverse phase high-performance liquid chromatography (RP-HPLC). The highest phenolic acid variability and content were detected in the standard melon. Sugar and organic acid compositions of melon cultivars were tested by capillary electrophoresis, and significant differences in types and contents of individual sugars and organic acids were determined among the cultivars. Standard Cinikiz Cumra melons had the highest ascorbic acid, total phenolics, and total sugar contents. The fructose/glucose ratio increased three times in grafted melon as compared with standard melon. While sugar alcohol mannitol existed in the standard and hybrid cultivars, this constituent disappeared in the grafted types. Citric acid found in the standard cultivar was not detected in the hybrid and grafted types. Consequently, it was concluded that the nutritional value of melons changed by the application of hybridization, grafting, or standard (open pollinated) production methods. The standard melon was found to have the highest score in terms of taste, because of its highest sweetness and sourness. It was also found preferable because of its high antioxidant activity, total phenolic and ascorbic acid contents.

Hepatoprotective Potential of Chestnut Bee Pollen on Carbon Tetrachloride-Induced Hepatic Damages in Rats

Bee pollen has been used as an apitherapy agent for several centuries to treat burns, wounds, gastrointestinal disorders, and various other diseases. The aim of our study was to investigate the hepatoprotective effects of chestnut bee pollen against carbon tetrachloride (CCI4)-induced liver damage. Total phenolic content, flavonoid, ferric reducing/antioxidant power, and DPPH radical activity measurements were used as antioxidant capacity determinants of the pollen. The study was conducted in rats as seven groups. Two different concentrations of chestnut bee pollens (200 and 400 mg/kg/day) were given orally and one group was administered with silibinin (50 mg/kg/day, i.p.) for seven days to the rats following the CCI4 treatment. The protective effect of the bee pollen was monitored by aspartate transaminase (AST) and alanine transaminase (AST) activities, histopathological imaging, and antioxidant parameters from the blood and liver samples of the rats. The results were compared with the silibinin-treated and untreated groups. We detected that CCI4 treatment induced liver damage and both the bee pollen and silibinin-treated groups reversed the damage; however, silibinin caused significant weight loss and mortality due, severe diarrhea in the rats. The chestnut pollen had showed 28.87 mg GAE/g DW of total phenolic substance, 8.07 mg QUE/g DW of total flavonoid, 92.71 mg Cyn-3-glu/kg DW of total anthocyanins, and 9 mg β-carotene/100 g DW of total carotenoid and substantial amount of antioxidant power according to FRAP and DPPH activity. The results demonstrated that the chestnut bee pollen protects the hepatocytes from the oxidative stress and promotes the healing of the liver damage induced by CCI4 toxicity. Our findings suggest that chestnut bee pollen can be used as a safe alternative to the silibinin in the treatment of liver injuries.

Evaluation of the antioxidant activity of three varieties of honey from different botanical and geographical origins.

It is well established that honey contains substantial antioxidant compounds that could protect cell components from the harmful action of free radicals. One can speculate that these compounds may strengthen the organism defenses and consequently prevent oxidative stress in humans. Therefore, over time, impaired cells can accumulate and lead to age-related diseases. A comparative study was carried out to assess the antioxidant activity of three varieties of honey from different botanical and geographical (Manuka honey from New Zealand, Acacia Honey from Germany and Wild carrot honey from Algeria). Manuka honey had the highest phenolic content with 899.09 ± 11.75 mg gallic acid/kg. A strong correlation between the antioxidant activities of honeys and their total phenol contents has been noticed.

Inhibition of carbonic anhydrase isozymes I and II with natural products extracted from plants, mushrooms and honey

Different natural products and secondary metabolites from mushrooms, teas, honeys, mosses, plants and seaweeds were investigated for their in vitro inhibitory effects on human carbonic anhydrase (hCA, E.C.4.2.1.1) isoforms I and II. Inhibition data were correlated with the total phenol content in the extract and investigated with the pure compounds believed to be responsible for this activity. Methanolic extracts were prepared for 17 such pure chemicals present in the natural products and for 41 diverse natural products. The IC50 values were in the range of 0.11–66.50 μg/mL against hCA I and of 0.09–54.54 μg/mL against hCA II, respectively. The total phenol content was in the range of 0.02–1318.96 (as milligrams of gallic acid equivalents) per gram of sample. These data offer new insights on possible novel classes of CA inhibitors based on natural products, possessing a range of chemical structures not present in the classical inhibitors with pharmacological applications, such as the sulfonamides and sulfamates.

Total monoamine oxidase (MAO) inhibition by chestnut honey, pollen and propolis

Abstract Monoamine oxidase (MAO) inhibitors are generally used in the treatment of depressive disorders and some neurodegenerative illnesses, such as Parkinson’s disease and Alzheimer’s disease. The aim of this preliminary study was to investigate the MAO [MAO (E.C.1.4.3.4)] inhibiting effect of various apitherapeutic products, such as chestnut honey, pollen and propolis. Extracts’ MAO inhibition was measured using peroxidase-linked spectrophotometric assay in enzyme isolated from rat liver microsomes, and the values are expressed as the inhibition concentration (IC50) causing 50% inhibition of MAO. The antioxidant activity of the bee products was also determined in terms of total phenolic content (TPC) and ferric reducing/antioxidant power in aquatic extracts. All samples exhibited substantial inhibition of MAO, propolis having the highest. Inhibition was related to samples’ TPCs and antioxidant capacities. These results show that bee products possess a sedative effect and may be effective in protecting humans against depression and similar diseases.