Isolation and Structure Elucidation of Vinca Alkaloids From Vinca Species and Investigation Of Cytotoxic Activity of Vinorelbine Loaded Nanodrug Delivery Systems

Tez Türü: Doktora

Tezin Yürütüldüğü Kurum: İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Organic Chemistry, Türkiye

Tez Danışmanı: Gülaçti Topçu

Tezin Onay Tarihi: 2011

Tezin Dili: İngilizce

Desteklendiği Program: Diğer

Özet:

This thesis study mainly consists of two different parts. The first part forms isolation and structure elucidation of Vinca alkaloids from the three Vinca species (Vinca major, Vinca minor and Vinca soneri). The second part consists of loading of a dimeric Vinca alkaloid, Vinorelbine to three different types of micellar nano-drug delivery systems (MNDDS) and physical characterization of MNDDS and investigation of their cytotoxic activity.

As it is known, natural products or their derivatives have an important place in cancer therapy. Among present chemotherapeutic agents natural drugs or their semi-synthetic derivatives, namely alkaloids from Taxus, Catharantus and Vinca species are the most common drugs. Particularly dimeric Vinca alkaloids which have indeed Catharantus alkaloids and their derivatives are used in lung, ovarian and breast cancer therapy. However, all of the anti-cancer drugs including Vinca alkaloids have numerous side-effects. For this purpose, both isolation and structure elucidation studies for the Vinca alkaloids growing in Turkey were carried out, and the three micellar drug delivery systems were prepared and investigated for their physical properties and cytotoxic activity of the MNDDS with and without Vinorelbine.

For the phytochemical research, alkaloids’ extracts of the three Vinca species were prepared, and structure of alkaloids, isolated by chromatographic methods, were determined with modern spectroscopic techniques, namely NMR (¹H and ¹³C NMR, BB, APT, DEPT, COSY, gHSQS and gHMBC) and mass spectroscopy. From the three Vinca species, Vinca soneri has just been brought to the world of science as a new endemic species to Turkey. In fact, there are four species of Vinca in Turkey and among them, investigations on V. herbacea have just now published by our group. Vallesiachotamine and Picrinine were isolated from Vinca soneri as well as α and β-Yohimbine. Vallesiachotamine is also isolated from Vinca minor besides iso-Vallesiachotamine. This is the first isolation of Vallesiachotamine, iso-Vallesiachotamine, α and β-Yohimbine from Vinca species as known Indole alkaloids. It is noteworthy that 11-Hydroxypolyneuridine was obtained from V. major as a new Indole alkaloid in this study.

The studies of the second part are the preparation of the Vinorelbine nanoformulations. Vinorelbine is uploaded to one lipid-based and two polymeric nano-drug delivery systems. The aim of these formulations is to prepare drug delivery systems which target cancerous tissue by using Enhanced Permeability and Retention (EPR) effect with high efficiency and lesser side effects.

One of the MNDDS used in this study is a very well known targeting carrier, DiStearoyl PhosphatidylEthanolamine-PolyEthyleneGlycol 2000 (DSPE-PEG 2000) which has been used in targeted cancer therapy researches, reported several times.

We also used two different Polymeric MNDDS to produce Nano-VLB. One of them is four-arm star-shaped Poly-ε-Caprolactone (PCL), PolyEthyleneGlycol (PEG) (PCL₄-PEG₄), and the other one is Y shaped PCL₂-PEG. These polymers have been synthesized by Prof. Gurkan HIZAL and Umit TUNCA polymer research group and the synthesis procedure was not involved in this study. The structure and synthesis pathway of these two polymers are new and we are reporting the characterization of micelles prepared by these two co-polymers.

For the characterization of these two polymeric micelles their CMC were investigated and gave satisfactory results (CMC is 50 mg/L and 1mg/L for Star and Y-Shaped PCL-PEG micelles, respectively) and we are introducing two new drug delivery systems for hydrophobic agents by preparing two new Nano-VLB formulations.

As a result, although both polymeric nano-VLB formulations and DSPE-PEG formulation showed enhanced in vitro cytotoxic activity, the latter one exhibited higher activity and drug loading capacity than the former one. Thus, it can be summarized that DSPE-PEG systems can be considered as better drug delivery systems, at least based on our experimental results as well as the accumulated knowledge.