Synthesis, characterization and biochemical studies of some steriods, indomethacin and pyrimidine analogues as inhibitors of CYP 450 17-hydroxylase, HIV, HCV and kinesin EG5 enzyme

Other Title(s)

تحضير و تشخيص و دراسة حيوية-كيميائية لنظائر بعض السترويدات و الأندوميثاسين و البايريميدين كمثبطات أنزيم الفا-هيدروكسيلاز و فايروس نقص المناعة المكتسبة و فايروس التهاب الكبد الفايروسي و أنزيم الكينيزين

Dissertant

al-Dubun, Dawud Salman Ali

Thesis advisor

al-Masudi, Najm Abbud Luaybi

Comitee Members

al-Zamily, Awdah Mizil Yasir
Awdah, Muhammad Ajah
Radi, Hanan Abd al-Jalil
al-Asadi, Iqbal Jasim Badr
Abd al-Rida, Nabil Abd

University

University of Basrah

Faculty

Science College

Department

Department of Chemistry

University Country

Iraq

Degree

Ph.D.

Degree Date

2013

English Abstract

Several steroid, and pyrimidine derivatives have long been known for diverse potential biochemical properties, mainly as antitumor and antiviral agents, meanwhile indomethacin is known as an antiinflammatory drug.

The present thesis is concerned with the synthesis and biochemical studies of new analogues of these potent bioactive molecules on various tumour and viruses enzymes and accordingly the thesis is divided into six chapters. The first chapter focus on the biochemical and crystal structure, biosynthesis and reactions of the cytochrome P450 (CYP) enzyme system in the living cells.

It consists of a superfamily of hemoproteins that catalyse the oxidative metabolism of a wide variety of exogenous chemicals including drugs, carcinogens, toxins and endogenous compounds such as steroids, fatty acids and prostaglandins. Cytochrome 450 17-hydroxylase enzyme (CYP171A) catalyzes the steroid biosynthesis pathway by the conversion of pregnenolone to 17-hydroxypregnenolone, which is subsequently converted to C19 steroid dehydroepi-androsterone, a compound with androgenic activity, whereas androgens are potent prostate mitogens and their level elevation would be associated with prostate cancer.

The steroidal CYP17 inhibitors, e.g.: androstanes, pregnanes, abiraterone and galetrone have been described.

In addition, the biochemical properties and their biological importance of various cholesteryl analogues have been reviewed.

The biochemical of the anti-inflammatory drug 'indomethacin' as a cyclooxygenase (COX) inhibitor, as well as the biological importance of its derivatives against various diseases have been screened.

The metabolism and biological applications of pyrimidines as nucleobases of RNA and DNA were described, whereas the scopes of its applications as antibacterial, antiviral, antifungal and antitumor drugs have been studied. The third chapter describe the synthetic pathways of new steroids: novel pregnenolone analogues bearing substituted thiadiazole-imine groups at C-20, arylsulphonates and arylamide moieties at C-3, in addition to the cholestesryl analogues having thioureido amino acid residues prepared, subsequently from the reaction of the cholesteryl chloroformate with ammonium thiocyanate followed by its treatment with various amino acid esters.

The work in chapter four describes the synthesis of a new series of aryl-indomethacin analogues prepared by substitution of the chloro residue by aryl groups employing Suzuki cross-coupling reaction.

The work is extended to functionalize the acid group by the synthesis of a new series of indomethacin analogues having thioureido-L-amino acid and amide (of Lamino acid) moieties. Chapter five is concerned with the synthesis of new potentially active 2-amino-6-aryl-4- benzylpyrimidines, from the reaction of 6-chloro-pyrimine backbone with arylboronic acids using Suzuki cross-coupling reaction conditions. The main object of the thesis is given in chapter six which focus mainly on the biochemical studies including: inhibition activity, mechanism action, structural and molecular docking interaction study as well as the QSAR of the new bioactive compounds of pregnenolone, cholesterol, indomethacin and pyrimidine on the cytochrome 450 (CYP171A), human immunodeficiency virus (HIV), hepatitis virus type C (HCV) and the motor protein kinesin Eg5. Prostate cancers (PCs) are androgen dependent and androgen receptor antagonists and GnRH analogues that have been recently used to treat these tumors, though with limited success, meanwhile the enzyme CYP171A, catalysis the key step in androgen formation, therefore its inhibition affects both testicular as well as adrenal androgen formation and finally will reduce the PCs.

Therefore, the aim of our work is to develop highly active and selective CYP17 1A inhibitors.

The preliminary study on the new synthesized pregnenolone analogues bearing substituted imino-substituted-thiadiazoles showed a remarkable inhibition of CYP17 enzyme, where the analogue 143.

In conclusion, the electron donating substituents (like methoxy group in 143) would increase the iron-complexing imine and thiadiazole nitrogen atoms interaction, as well as the hydrogen bonding and hydrophobic interactions with the amino acids of CYP17, as shown from the docking modelling study. Click to buy NOW! PDF-XChange Viewer www.docu-track.com Interestingly, the other analogues 142-146 and 156 showed a 75-83% inhibition at 50 μM, which means that these analogues showed a much higher selectivity than abiraterone itself.

Furthermore, the QSAR of these derivatives has been studied extensively. Our biochemical study is extended to the antiviral screening study, where the new pregnenolone, cholesteryl, indomethacin and pyrimidine analogues have been tested against the activity of HIV type 1 and 2.

The in vitro screening data, using MTT assay, showed that 168, 176, 217 and 225 were found to be the most active analogues from the series inhibiting HIV-1 and HIV-2 replication in a cell culture, and proposed to act as nonnucleoside reverse transcriptase inhibitors (NNRTIs), since the molecular docking of 178 revealed several HB and hydrophobic interactions. Since the hepatitis virus type C (HCV) infection is a major cause of liver failure, and is responsible for the majority of liver transplants, several drugs have been used (e.g.: combination of ribavirin and inferone-2) are currently the only marketed drugs with severe side effect.

Our attention has been focused on the biochemical study of our cholesteryl and indomethacin analogues, where the analogue 175 exhibited a potential activity to inhibit HCV in the Huh 5-2 replicon system (type 1b, Con1 strain) with EC50 of 5.09 μM and CC50 = 39 μM against HCV and resulting in SI = 7.65.

The molecular docking modelling study showed an interesting HB and hydrophobic interaction with the HCV amino acids. Moreover, the inhibition behaviour of these analogues during the screening process has been studied. Several members of the kinesin family of microtubule motor proteins play essential roles in mitotic spindle function and are potential targets for the discovery of novel antimitotic cancer therapies. A part of our work is denoted to the investigation of the mechanism of inhibition of Eg5 (kinesin spindle protein) by our new synthesized products as new Eg5 inhibitors via , inhibiting the ATP hydrolysis cycle of Eg5.

The analogue 224 exhibited remarkable antimitotic activity of IC50 = 2.45 , with a ATPase inhibition value of 65% at 100 μM concentration compounds, in comparison to the antimitotic drug monastrol 239 with arrest velocity ~ 0.75 mm/min.

Such a result revealed that 224 can act as a new model in cancer chemotherapy as a structurally resemblance monastrol 239 and can induce the accumulation of mitotic cells with monopolar spindles in tumor tissues.

Main Subjects

Chemistry

No. of Pages

288

Table of Contents

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Language

English

Data Type

Arab Theses

Record ID

BIM-744381