Turgay Cakmak

Analysis of apoplastic and symplastic antioxidant system in shallot leaves: Impacts of weak static electric and magnetic field

Impacts of electric and magnetic fields (EFs and MFs) on a biological organism vary depending on their application style, time, and intensities. High intensity MF and EF have destructive effects on plants. However, at low intensities, these phenomena are of special interest because of the complexity of plant responses. This study reports the effects of continuous, low-intensity static MF (7 mT) and EF (20 kV/m) on growth and antioxidant status of shallot (Allium ascalonicum L.) leaves, and evaluates whether shifts in antioxidant status of apoplastic and symplastic area help plants to adapt a new environment. Growth was induced by MF but EF applied emerged as a stress factor. Despite a lack of visible symptoms of injury, lipid peroxidation and H₂O₂ levels increased in EF applied leaves. Certain symplastic antioxidant enzyme activities and non-enzymatic antioxidant levels increased in response to MF and EF applications. Antioxidant enzymes in the leaf apoplast, by contrast, were found to show different regulation responses to EF and MF. Our results suggest that apoplastic constituents may work as potentially important redox regulators sensing and signaling environmental changes. Static continuous MF and EF at low intensities have distinct impacts on growth and the antioxidant system in plant leaves, and weak MF is involved in antioxidant-mediated reactions in the apoplast, resulting in overcoming a possible redox imbalance.

Induction of triacylglycerol production in Chlamydomonas reinhardtii: Comparative analysis of different element regimes

In this study, impacts of different element absence (nitrogen, sulfur, phosphorus and magnesium) and supplementation (nitrogen and zinc) on element uptake and triacylglycerol production was followed in wild type Chlamydomonas reinhardtii CC-124 strain. Macro- and microelement composition of C. reinhardtii greatly differed under element regimes studied. In particular, heavy metal quotas of the microalgae increased strikingly under zinc supplementation. Growth was suppressed, cell biovolume, carbohydrate, total neutral lipid and triacylglycerol levels increased when microalgae were incubated under these element regimes. Most of the intracellular space was occupied by lipid bodies under all nutrient starvations, as observed by confocal microscopy and transmission electron micrographs. Results suggest that sulfur, magnesium and phosphorus deprivations are superior to nitrogen deprivation for the induction triacylglycerol production in C. reinhardtii. On the other hand, FAME profiles of the nitrogen, sulfur and phosphorus deprived cells were found to meet the requirements of international standards for biodiesel.

Nitrogen and sulfur deprivation differentiate lipid accumulation targets of Chlamydomonas reinhardtii

Nitrogen (N) and sulfur (S) have inter-related and distinct impacts on microalgal metabolism; with N starvation having previously been reported to induce elevated levels of the biodiesel feedstock material triacylglycerol (TAG), while S deprivation is extensively studied for its effects on biohydrogen production in microalgae.1,2 We have previously demonstrated that N- and S-starved cells of Chlamydomonas reinhardtii display different metabolic trends, suggesting that different response mechanisms exist to compensate for the absence of those two elements.3 We used C. reinhardtii CC-124 mt(-) and CC-125 mt(+) strains to test possible metabolic changes related to TAG accumulation in response to N and S deprivation, considering that gamete differentiation in this organism is mainly regulated by N.4 Our findings contribute to the understanding of microalgal response to element deprivation and potential use of element deprivation for biodiesel feedstock production using microalgae, but much remains to be elucidated on the precise contribution of both N and S starvation on microalgal metabolism.

Optimization of ultrasonic-assisted extraction via multiresponse surface for high antioxidant recovery from Chlorella vulgaris (Chlorophyta)

Abstract: The present study reports on the extraction of antioxidant compounds from Chlorella vulgaris. Multiresponse surface methodology coupled with a central composite design was used to optimize the independent parameters for ultrasonic-assisted extraction (UAE). Four independent parameters were optimized, including extraction time (15–155 min), ethanol volume (35–95%, v/v), extraction temperature (15–75°C) and liquid/solid ratio (30–150 ml g−1). Total phenolic content and antioxidant capacity [2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) and chromium-reducing antiaoxidant capacity methods] were considered response parameters, whereas the effects of extraction time, ethanol volume, extraction temperature and liquid/solid ratio were studied. The optimal condition was obtained with an extraction time of 146 min, ethanol volume of 71% (v/v), extraction temperature of 72°C and liquid/solid ratio of 62 ml g−1 of sample. The experimental values agreed with predicted values within a 95% confidence level. This indicates that multiresponse surface methodology is suitable for optimizing UAE of antioxidant compounds from C. vulgaris.

Production and characterization of spherical thermostable silver nanoparticles from Spirulina platensis (Cyanophyceae)

Abstract: Biological production of silver nanoparticles (SNP) has recently received considerable attention because of their therapeutic applications. The present study reports the production and characterization of spherical-thermostable SNP from Spirulina platensis. Wet biomass harvested from optimized logarithmic-phase culture was used for production of SNP in 1, 3, or 5 mM silver nitrate solution. Formation and concentration of spherical SNP was highest when S. platensis was treated with 3 mM silver nitrate. Fourier transform infrared spectra of SNP indicate that vanillin, coumarins, tannins, amide, and glycogen may act as stabilizing agents for bioreduction. The crystalline nature of the produced SNP was evidenced from X-ray diffractometer analysis. Weight loss of SNP occurred at 210°C, 310°C, and 510°C as shown by thermogravimetric analysis. This study shows that S. platensis may be used as an efficient tool for production of spherical, crystalline, and thermostable SNP.

Antioxidant response of Chlamydomonas reinhardtii grown under different element regimes

Nutrient stress is one of the most favorable ways of increasing neutral lipid and high value‐added output production by microalgae. However, little is known about the level of the oxidative damage caused by nutrient stress for obtaining an optimal stress level for maximum production of specific molecules. In this study, the antioxidant response of Chlamydomonas reinhardtii grown under element deprivation (nitrogen, sulfur, phosphorus and magnesium) and supplementation (nitrogen and zinc) was investigated. All element regimes caused a decrease in growth, which was most pronounced under N deprivation. Element deprivation and Zn supplementation caused significant increases in H2O2 and lipid peroxidation levels of C. reinhardtii. Decrease in total chlorophyll level was followed by an increase of total carotenoid levels in C. reinhardtii under N and S deprivation while both increased under N supplementation. Confocal imaging of live cells revealed dramatic changes of cell shape and production of neutral lipid bodies accompanied by a decrease of chlorophyll clusters. Antioxidant capacity of cells decreased under N, S and P deprivation while it increased under N and Zn supplementation. Fluctuation of antioxidant enzyme activities in C. reinhardtii grown under different element regimes refers to different metabolic sources of reactive oxygen species production triggered by a specific element absence or overabundance.

Computational Screening of Anti-diabetic molecules from Microalgae Metabolites by Molecular docking

The present study aimed to evaluate the efficiency of microalgae metabolites as a ligand for anti-diabetic target proteins namely Glucokinase, Fructose-1, 6-bisphosphatase, Glycogen synthase kinase, Cytochrome P450, multi-drug resistant protein, and Peroxisome proliferators activated receptor-γ (PPARγ) using computational approach. Three-dimensional structure of microalgal metabolites retrieved from Pub Chem database and the energy minimized. The active site of target protein predicted through PDB sum. Molecular docking has performed with microalgae metabolites using Hex 8.0 and DockThor server. Hex docking revealed binding fucoxanthin was higher with fructose 1,6 bis-phosphatase (-298.31), human multidrug resistant protein 1 (-369.67), and PPARγ (-404.18). DockThor docking suggested Zeaxanthin with Glucokinase produced higher total energy (111.23 kcal/mol) and interaction energy (-2.99 kcal/mol). Lutein with fructose 1,6 bisphosphatase, human multidrug resistant protein, glycogen synthase kinase, PPARγ, and cytochrome p450 produced higher total energy and interaction energy. Further studies will assess the anti-diabetic effect of carotenoids of microalgae, especially Lutein, Zeaxanthin, and Fucoxanthin. *Corresponding author: Dr. Turgay Cakmak, Phytoprocess Laboratory, Department of Molecular Biology and Genetics, Faculty of Engineering and Natural Sciences, Istanbul Medeniyet University, Istanbul, Turkey, Email: turgay.cakmak@medeniyet.edu.tr Dr. Gurudeeban Selvaraj, Phytoprocess Laboratory, Department of Molecular Biology and Genetics, Faculty of Engineering and Natural Sciences, Istanbul Medeniyet University, Istanbul, Turkey, Tel: +90-216-280-3505, Fax: 90-216-280-2021 Email: gurudeeb99@gmail.com Received Date: November 29, 2016 Accepted Date: December 28, 2016 Published Date: January 09, 2017

Computational screening of dipeptidyl peptidase IV inhibitors from micoroalgal metabolites by pharmacophore modeling and molecular docking

Dipeptidyl peptidase IV (DPP‐IV) catalyzes conversion of GLP‐1 (glucagon like peptide 1) to inert structure, which results in insufficient secretion of insulin and increase in postprandial blood glucose level. The present study attempts to identify novel inhibitors from bioactive metabolites present in microalgae against DPP‐IV through virtual screening, molecular docking, and pharmacophore modeling for the active target. Possible binding modes of all 60 ligands against DPP‐IV receptor were constructed using MTiOpenScreen virtual screening server. Pharmacophore model was built based on identified 38 DPP‐IV test ligands by using the web‐based PharmaGist program which encompasses hydrogen‐bond acceptors, hydrophobic groups, spatial features, and aromatic rings. The pharmacophore model having highest scores was selected to screen active DPP‐IV ligands. Highest scoring model was used as a query in ZincPharmer screening. All identified ligands were filtered, based on the Lipinskis rule‐of‐five and were subjected to docking studies. In the process of docking analyses, we considered different bonding modes of one ligand with multiple active cavities of DPP‐IV with the help of AutoDock 4.0. The docking analyses indicate that the bioactive constituents, namely, β‐stigmasterol, barbamide, docosahexaenoic acid, arachidonic acid, and harman showed the best binding energies on DPP‐IV receptor and hydrogen bonding with ASP545, GLY741, TYR754, TYR666, ARG125, TYR547, SER630, and LYS554 residues. This study concludes that docosahexaenoic acid, arachidonic acid, β‐stigmasterol, barbamide, harman, ZINC58564986, ZINC56907325, ZINC69432950, ZINC69431828, ZINC73533041, ZINC84287073, ZINC69849395, and ZINC10508406 act as possible DPP‐IV inhibitors.