Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Effects of Centella Asiatica Saponins on Telomerase Activation and Wound Healing(Izmir Institute of Technology, 2021) Demirbaş, Devran; Büyükkileci, Ali Oğuz; Bedir, Erdal; Bedir, Erdal; Büyükkileci, Ali Oğuz; 03.01. Department of Bioengineering; 01. Izmir Institute of Technology; 03.08. Department of Food Engineering; 03. Faculty of EngineeringCentella asiatica L. is a well-known plant species endemic to Southeast Asia that has noteworthy biological effects. Triterpenoid saponins, comprising more than 80% of the content, are suggested to be the chief compounds responsible for the biological effects. A recent study has described that the extract of Centella asiatica exhibits telomerase activation. In line with these developments, as part of our studies on natural products demonstrating anti-aging properties, we decided to engage Centella asiatica and its components. Within the scope of this thesis, four major compounds, viz. madecassoside, asiaticoside, madecassic acid, and asiatic acid were isolated from the standardized extract of Centella asiatica, and their structures were elucidated by spectroscopic methods. Using in vitro methods, the effects of the extract and purified compounds on cell proliferation under standard culture and oxidative stress (H2O2) conditions, wound healing, and human Telomerase Reverse Transcriptase (hTERT) protein level were investigated. Our experiments were conducted on MRC-5 and HEKn cell lines. It was observed that the standardized extract of Centella asiatica increased the proliferation of the MRC-5 cells meaningfully between 5 to 100 µg/ml. Moreover, the extract showed protective effects on MRC-5 cells at 500 and 1000 ng/ml under oxidative stress conditions. Madecassoside, madecassic acid, asiaticoside, and asiatic acid exhibited the highest proliferative effects on MRC-5 cells at concentrations of 1000 nM (28%), 2 nM (66%), 300 nM (61%), and 300 nM (56%), respectively. Asiatic acid and the extract accelerated cell migration in wound areas that were made on MRC-5 cells up to 32% and 36% in the range of 10 to 300 nM or ng/ml, respectively. The immunoblotting assay studies showed that madecassoside and asiaticoside were increased the expression of hTERT protein level on HEKn cell line by 3.16-fold and 5.62-fold, respectively, at 30 nM concentration. Furthermore, the extract was observed to increase the protein level by 2.62-fold at 300 ng/ml.Master Thesis Investigating Immunomodulator Mechanisms of Astragalus Saponins(Izmir Institute of Technology, 2018) Yakuboğulları, Nilgün; Yakuboğulları, Nilgün; Bedir, Erdal; Bedir, Erdal; Sağ, Duygu; 01.01. Units Affiliated to the Rectorate; 03.01. Department of Bioengineering; 01. Izmir Institute of Technology; 03. Faculty of EngineeringAdjuvants are chemical/biological substances that are used in vaccines to increase immunogenicity of antigens. Astragaloside VII (AST VII), a triterpenoid saponin isolated from Astragalus species, stimulates Th1 mediated immune response with antigen specific antibody response. The main goals of this thesis are synthesis of immunologically active analogs of AST VII and identifying immunomodulatory mechanism of actions of AST VII. The impact of AST VII and its synthesized analogs (dicarboxylic AST VII: DC-AST VII and dodecylamine conjugated AST VII: DAC-AST VII) on the cytokine release profile of human whole blood cells (hWB), dendritic cell maturation and subsequently T cell activation were analyzed by using flow cytometry and ELISA. IL-1 and IL-17A cytokines were substantially induced on hWB following treatments of the compounds. The most potent compounds were: DAC-AST VII (3.32 fold) for production of IL-1, AST VII (5.05 fold) for production of IL-17A. AST VII was more effective than DAC-AST VII (7.52 fold versus 1.34) in IL-1 production in BMDCs (bone marrow derived dendritic cells). The co-stimulation with AST VII and LPS enhanced dendritic cell maturation and activation by upregulating MHC II, CD86 and CD80, as well as IL-12 induction. All compounds were able to activate CD4+ and CD8+ T cells via increasing CD44 expression. Inflammasome activation may have a role in AST VII induced IL-1 secretion, dendritic cell maturation and T cell activation. However, more detailed molecular mechanism studies are warranted to substantiate our findings and to put forward signaling pathways involved.