ABSTRACT

The synthesis of N-heteroaryl substituted benzene sulphonamides and evaluation of their biological activities are reported. Synthesis was achieved by the reaction of benzene sulphonyl chloride and substituted amino heterocycle in dry pyridine. The structures of synthesized compounds were assigned by spectroscopic methods. The eight (8) synthesized compounds were evaluated for antibacterial and antifungal activities. The results showed that some of the new compounds exhibited activities comparable to ciprofloxacin and ketoconazole. Acute toxicity (LD₅₀) of the synthesized samples was carried out_. Malaria parasitaemia was inoculated in the mice using parasitized blood from infected mice. The synthesized compounds were used at dose 2000 mg/kg body weight of mice. The antioxidant effects were determined using the antioxidant enzymes: superoxide dismutase (SOD), catalase and glutathione. Some of the new compounds displayed significant antioxidant properties. The parameters; alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzymes activities were used for liver function test while serum urea and creatinine tests were used as markers for renal function. The results of the activities of the synthesized compounds showed appreciable inhibition of the growth of test organism. The liver and kidney function tests showed improved activity when compared with the positive control.

 

 

 

TABLE OF CONTENTS

Title page                                                                                                                    i

Certification                                                                                                                ii

Dedication                                                                                                                  iii

Acknowledgement                                                                                                      iv

Abstract                                                                                                                      v

Table of content                                                                                                          vi

List of the Tables                                                                                                        x

List of the Schemes                                                                                                    xi

List of the Figures                                                                                                       xii

List of the Abbreviations                                                                                            xv

 

CHAPTER ONE

1.1       Introduction                                                                                                    1

1.2       background of study                                                                                       2

1.2.0    Classification of Sulphonamides                                                                    7

1.2.1    Short Acting Sulphonamides                                                                          7

1.2.2    Intermediate or Moderate Acting Sulphonamides                                         8

1.2.3    Long Acting Sulphonamides                                                                          8

1.3       Statement of the problem                                                                               9

1.4       Objectives of the study                                                                                   10

1.5       Justification of the study                                                                                10

 

CHAPTER TWO

2.1       Literature review                                                                                             12

2.2.1    Synthesis of sulphonamides                                                                            12

2.2.2    Sulphonamides from sulphonyl chlorides                                                       13

2.2.3    Sulphonamides from sulphonic acids                                                             14

2.2.4    Sulphonamides from sulphenamides                                                              16

2.2.5    Sulphonamides from sulphonate esters                                                           17

2.2.6    Sulphonamides from N-arylation                                                                    21

2.3.1    Applications of the Sulphonamides                                                                23

2.3.2    Sulphonamides as Drugs                                                                                 25

2.2.2    Sulphonamides as antibacterial agents                                                            25

2.2.3    Sulphonamides as HIV inhibitors                                                                   26

2.2.4    Sulphonamides as cysteine protease inhibitors                                               28

2.2.5    Sulphonamides as COX – II specific                                                             32

2.2.6    Sulphonamides as carbonic anhydrase                                                            33

 

CHAPER THREE

3.0       Experimental                                                                                                   37

3.1       General                                                                                                            37

3.2       General Procedures                                                                                         37

3.3       Determination of the Antimicrobial Activity                                                 37

• Sensitivity Testing of Compounds. 38

3.4.2    Minimum Inhibitory Concentration (MIC) Testing of Compounds.              38

3.5.1    Acute Toxicity Studies (LD₅₀)                                                                        39

3.5.2    Experimental protocol for Acute Toxicity Studies                                         39

3.5.3    Experimental Design                                                                                       39

3.6.1    Inoculation of Parasitaemia                                                                            40

3.6.2    Determination of the Malaria parasite (Mp⁺)                                                  41

3.7.0    Determination of the Antioxidant activity:                                                    41

3.7.1    Determination of the Superoxide Dismutase (SOD)                                      41

3.7.2    Determination of the Catalase                                                                                   41

3.7.3    Determination of the Glutathione                                                                   42

3.8.0    Determination of the Liver Function Test activity:                                        42

3.8.1    Determination of the Aspartate Aminotransferase (AST) Activity                42

3.8.2    Determination of the Alanine Aminotrasferase (ALT) Activity                    43

3.9.0    Determination of the Kidney Function Test activity:                                     44

3.9.1    Determination of the Urea                                                                              44

3.9.2    Determination of the Creatinine                                                                     45

3.10.1  N– (pyridin – 2 -yl)benzene sulphonamides                                                     45

3.10.2  N– (4-methylpyridin – 2 -yl)benzene sulphonamides                                       45

3.10.3  N– (3-nitropyridin – 2 -yl)benzene sulphonamides                                          46

3.10.4  N– 5-nitropyridin – 2 -yl)benzene sulphonamides                                           46

3.10.5  N– (3-hydroxypyridin – 2 -yl)benzene sulphonamides                                    46

3.10.6  N– (5-chloropyridin – 2 -yl)benzene sulphonamides                                        46

3.10.7  N– (2,6-dichloropyridin – 2 -yl)benzene sulphonamides                                 47

3.10.8  N– (3,5-dichloropyridin – 2 -yl)benzene sulphonamides                                 47

 

CHAPER FOUR

4.0       Results and discussion                                                                                    48

4.1.1    N– (pyridin – 2 -yl)benzene sulphonamides                                                     48

4.1.2    N-(4-methylpyridin–2-yl)benzene sulphonamide                                           49

4.1.3    N– (3-nitropyridin – 2 -yl)benzene sulphonamides                                          49

4.1.4    N– (5-nitropyridin – 2 -yl)benzene sulphonamides                                          50

4.1.5    N– (3-hydroxypyridin – 2 -yl)benzene sulphonamides                                    50

4.1.6    N– (5-chloropyridin – 2 -yl) benzene sulphonamides                                       51

4.1.7    N– (2,6-dichloropyridin – 2 -yl)benzen esulphonamides                                 51

4.1.8    N– (3,5-dichloropyridin – 2 -yl)benzene sulphonamides                                 52

4.2       Result of Antimicrobial Activity                                                                    52

4.3       Result of Acute Toxicity Study (LD₅₀)                                                          54

4.4       Result of Percentage Parasitaema                                                                   57

4.5.0    Result of determination of the Antioxidant Activity:                                                58

4.5.1    Result of determination of the Superoxide Dismutase (SOD)                       58

4.5.2    Result of determination of the Catalase                                                         59

4.5.3    Result of determination of the Glutathione                                                    60

4.6.0    Result of determination of the Liver Function Test Activity:                                    61

4.6.1    Result of Aspartate aminotranferasa (AST) Activity in Mice                        62

4.6.2    Result of Alanine aminotranferasa (ALT) Activity in Mice                           62

4.7.0    Result of determination of Kidney Function Test Activity:                          64

4.7.1    Result of Urea                                                                                                 64

4.7.2    Result of Creatinine                                                                                        65

4.4       Discussion                                                                                                       66

 

CHAPTER FIVE

5.0       Conclusions                                                                                                     69

5.2       Recommendation                                                                                            69

References                                                                                                            70

 

 

CHAPTER ONE

1.1       INTRODUCTION

The basic sulphonamide group –SO₂NH- occurs in various biological active compounds including antimicrobial drugs, antithyroid agents, antitumor antibiotics and inhibitors of carbonic anhydrase^1,2.  Sulphonamides are widely used to treat microbial infection by inhibiting the growth of gram-negative and gram-positive bacteria, some protozoa and fungi³. Clinically, sulphonamides are used to treat several urinary tract infections and gastrointestinal infections⁴. Sulphonamides that are aromatic or hetroaromatic are responsible for the inhibition of the growth of tumor cells. They act as antitumor agents by inhibiting carbonic anhydrase. Sulphonamides are structurally similar to p-aminobenzoic acid (PABA) which is a cofactor that in needed by the bacteria for the synthesis of folic acid. Sulphonamides antibiotics inhibit the synthesis of purine and DNA in the microorganism. Sulphonamide antibiotics are used as veterinary medicines to treat infections in livestock herds^5,6. Sulphonamides are extremely useful pharmaceutical compounds because they exhibit a wide range of biological activities such as anticancer, anti-inflammatory and antiviral functions^7-11. The sulphonylation of amines with sulphonyl chlorides in the presence of a base is still being used as the method of choice because of high efficiency and simplicity of the reaction¹². However, this approach is limited by the formation of undesired disulphonamides with primary amines and by the need of harsh reaction conditions for less nucleophilic amines such as anilines¹³. Additionally, side reactions take place in the presence of a base. Sulphonamides have been used as protecting groups of OH or NH functionalities for easy removal under mild conditions^14-15. In recent years, molecular iodine has been extensively used for a plethora of organic transformations as an inexpensive, nontoxic, readily available catalyst under very mild and convenient conditions to afford the corresponding products in excellent yields with high selectivity^16-22. This can be seen in the case of efficient molecular iodine catalyzed method developed for preparing sulphonamides (Scheme 1).

     Scheme1:  Synthesis of α-sulphonamide

1.2       Background of Study

Sulfa drugs are still today among the drugs first used (together with ampicillin and gentamycin) as chemotherapeutic agents in bacterial infections by Escherichia coli in humans²³. Sulfa drugs also known as sulphonamides have acquired a somewhat specific position in the family of organic sulphur compounds. This is largely due to their involvement in diverse area of utility, which include the pharmaceutical fields in which they are used as antidiabetic^24,25, antithyroid²⁶,etc. The first antibacterial compounds used were the sulphonamides and the antibacterial properties of the dyestuff, Prontosil rubrum were found to be associated with the sulphonamide group of the compound. Today, the sulphonamides have been largely replaced by the antibiotics. The main reasons for this are as follows: (i) antibiotics have greater potency and (ii) several strains of bacteria have acquired resistance to sulphonamides. Some of the compounds, however, are still in use. A large number of derivatives of sulphonamides have been prepared by substituting the hydrogen atoms of the amino radicals with other groups. The sulphonamides are bacteriostatic rather than bactericidal. Their value lies in their ability to slow down or prevent bacterial multiplication in wounds or infected systems without appreciable toxicity to the body tissues.

Scheme2:  Some Example of Sulphonamides Drugs (Prontosil).

They are useful in treatment of infections caused by staphylococci, streptococci, meningococci, and urinary infections caused by gram-negative bacteria. However, organisms develop resistance to sulphonamides in the course of therapeutic use: Those still used include sulfabenzamide, sulfamethoxazole, sulfacetamide, sulfasalazine, and sulfathiazole. Sulphonamides are of fundamental chemical interest as many of them possess pharmacological, fungicidal, or herbicidal activities. The sulphonamides in general are thought to have low potential for adverse health effects, supported by their long history of safe therapeutic use in humans. Acute toxic effects have been rarely reported and these compounds are also nongenotoxic and nonteratogenic in laboratory animals at concentrations similar to therapeutic levels in humans. It is well known that their biological properties correlate strongly with the structure and conformational properties of the respective compounds. Recently, a study has been reported on the geometric structure and conformation of benzene sulphonamides, C₆H₅SO₂NH₂, on the basis of combined study of gas electron diffraction (GED) and quantum chemical calculations²⁷. Calculations also show that the sterically unfavorable orientation of the NH₂ group is stabilized by intramolecular hydrogen bonds between O and H atoms of the sulphonamide group²⁸. We have recently reported on the quantum chemical studies of a particular set of sulphonamides (sulfaguanidine, sulfamethazine, sulfamethoxazole, and sulfadiazine) as corrosion inhibitors for mild steel in acidic medium using density functional theory (DFT) and some semi empirical methods and the correlation between the inhibition efficiency and the electronic properties of the studied molecules were discussed²⁹.

Sulphonamides were the first efficient treatment to be employed systematically for the prevention and cure of bacterial infections³⁰. Mechanistically, sulphonamides act as antimetabolites. They compete for incorporation with p-amino benzoic acid into folic acid. This principle introduced and sustained the concept of selective antagonism. Sulphonamides are widely used in medicinal chemistry because of their low cost, low toxicity and excellent biological activities. Many infectious diseases caused by bacteria are cured by widely use of sulphonamides³. In reported that various N-substituted derivatives of benzene sulphonamides had acetylcholinesterase, butyryl cholinesterase and lipoxygenase activities. Subhakara et al. has reported sulphonamides derived from C-8 alkyl chain of anacardic acid mixture isolated from cashew nut shellliquid to possess fascinating antibacterial activity³¹. So Subhrbera et al. has reported pazopanib hydrochloride containing a sulphonamide moiety as a potent and selective 5 multi-targeted receptor of tyrosinekinase that blocks tumour growth and inhibits angiogenesis³². Fors et al. has successfully used a new biarylphospine ligand (t-Bu Brettphos) for palladium catalyzed cross coupling reactions of 1-chloro-2-methylbenzene and acetamide to produce N-phenylacetamide. They reported that this system shows the highest turnover to date for the sereactions, especially for aryl chloride substrates bearing an ortho substituent⁷.

 

            Scheme3:  in vivoMetabolism of Prontosil

Apart from the commercialized application as antibacterial/antibiotic agents, various sulphonamides are also known to inhibit several enzymes such as carbonic anhydrase, cysteine protease, HIV protease and cyclooxygenase³³. Moreover, the widespread potential value of sulphonamides, have led to the discovery of various other therapeutic applications, in cancer chemotherapy, diuretics, hypoglyceamia and the anti- impotence agent Viagra³⁴.

Due to the inability of bacteria to acquire dihydrofolic acid from their environment, as part of bacteria’s DNA biosynthesis, inhibition of dihydrofolic acid synthase poses a desirable target for bacteriostatic agents (Scheme 3)³⁵. Inhibition of these enzymes has been achieved with early sulphonamides such as sulphanilamide 6. The formation of dihydrofolic acid is initiated by coupling pteridine diphosphate 7 with para-aminobenzoic acid 8, which can then undergo amide coupling with glutamic acid to form dihydrofolic acid 10. Sulphonilamide 6 displays similar core structure to that of p-aminobenzoic acid 8 and act as a competitive inhibitor. Dihydrofolic acid formation is interrupted during the second step; due to a lack of acidic terminal available to couple with glutamic acid, hence dihydrofolic acid 10 formations is interrupted³⁵.

 

Scheme4:  Inhibition of Dimethylformamide  formation by sulfanilamide

Later steps involve reduction to tetrahydrofolic acid using dihydrofolate reductase; however this step can also be inhibited using methotrexate 11 or trimethoprim 12 to enhance antibacterial activity, and it is commonly taken in conjunction to increase inhibitory activity and reduced dosage.

Scheme5: Structures of methotrexate and trimethoprim

            Sulphonamides are registered in Australia as antibacterials and are used widely in food producing animals because of their relatively low cost and ease of administration. Their use in veterinary medicine is wide spread, particularly as mass medicants for the control of diseases in food producing species. They are marketed in Australia either alone, or formulated in combination with other sulphonamides and/or antibiotics. They are presented as feed additives, or oral, topical, intrauterine pessaries and injectable preparations.

Sulphonamides are drugs commonly used to treat infectious diseases. Their development leads to a medical revelation in drug treatments^36-38. Sulphonamides exhibit broad range of biological activities³⁹. Several sulphonamides are used in therapy such as celecoxib, nimesulide, delavirdine, acetazolamide, methazolamide, furosemide, ethoxzolamide, dichlorphenamide, dorzolamide, brinzolamide, sulpiride, sotalol, tolbutamide, chlorpropamide, tolazamide, acetohexamide, glipizide, gliburide, glymidine, zonisamide, thiothixene and famotidine. Modifications of the sulphonamides have proven highly effective and modifications that have been made so far do not exhaust the possible changes that can be made to improve potency and efficacy of these sulphonamides. The present review highlights the recently synthesized sulphonamides possessing important potential biological activities. It would be interesting to see whether new sulphonamide derivatives can be utilized as potent therapeutic agents in future. Sulphonamides are compounds constituting diverse medicinal applications, widely used as antimicrobial^40,41, anticancer⁴², antiinflammatory⁴³ and antiviral agents as well as HIV protease inhibi-tors⁴⁴. Sulphonamides is well recognized as an antimetabolite⁴⁵.

The sulphonamides antimicrobial drugs were the first effective chemotherapeutic agents but the rapid development of widespread resistance diminished the usefulness of sulphonamides⁴⁶. An evaluation of azo dyes was done and prontosil was found to protect against, and cure, streptococcal infections in mice^47-50. The structure-activity study on the sulphonamide azo dyes was performed and the reductive cleavage of azo linkage to release the active antibacterial product, sulphonamides, was concluded^51,52. The chemistry of sulphonamides has been recently recognized in the preparation of various valuable biologically active compounds used especially as antibacterial agents⁵³. Today, sulphonamide – trimethoprim combinations are used extensively for opportunistic infections in patients with AIDS in addition to urinary tract infection and burn therapy^54-57. Resistance to sulphonamides by bacteria, is most likely as a result of a compensatory increase in the biosynthesis of p-aminobenzoic acid by bacteria although other mechanisms may play a role^58,59. Resistance of E Coli strains to sulphonamide has been shown due to their containing sulphonamide-resistant dihydropteroate synthase⁶⁰. Sulphonamides have highest powerful antibacterial activity for gram negative bacteria than gram- positive and antibacterial activity decreases as the length of the carbon chain increases⁴¹. Also, novel macrocyclic bis-sulphonamides were prepared and their antimicrobial activities were measured too. Bis-sulphonamide showed antibacterial activities against most strains tested⁶¹.

1.3.0    Classification of sulphonamides

Classifications of sulphonamides are based on chemical structure, duration of action, spectrum of activity and therapeutic applications. Common classification of sulphonamides is based on their therapeutic applications. There are three groups of sulphonamides according to their duration of Action

1.3.1    Short acting sulphonamides

These are preferred for systemic infections as they are rapidly absorbed and rapidly excreted. For example, sulphadiazine 13, sulphadimidine or sulphamethazine 14, and sulphamethoxazole 15 in (scheme 6) have been used for the treatment of urinary tract infections⁶².

 

 

1.3.2    Intermediate or moderate acting sulphonamides

These are used for infections requiring prolonged treatment. For example, sulphacetamide 16, sulphadoxine 17, etc (scheme 6). The sulphadoxine is an ultralonglasting sulphonamide often used in combination with pyrimethamine to treat or prevent malaria. It is also used, in combination with other drugs, to treat or prevent various infections in livestock⁶³.

1.3.3    Long acting sulphonamides

These are rapidly absorbed and slowly excreted. For example, sulphametopyrazine, sulphasalazine 18, which is marketed as azulfidine in the U.S. and salazopyrin & sulazine in Europe and Hong Kong, was developed over 70 years ago specifically to treat rheumatoid arthritis. Sulphasalazine is a derivative of mesalazine and is formed by combining sulphapyridine and salicylate with an azo bond. It may be abbreviated SSZ. Sulphasalazine is also used in the treatment of inflammatory bowel disease including ulcerative colitis and Crohn’s disease. In addition, there are different types of sulphonamides which have been used in various types of infections. For example, sulphabenzamide 19 used in mucous membrane, sulphacetamide sodium 20 used for superficial ocular, sulphadiazine 13 used in urinary tract infection and sulphamethizole 21 used in bacterial infections⁶⁴ (scheme 6).

 

 

 

 

 

Scheme 6:  Some Example of Sulphonamides

Previous studies showed that sulphonamides have being prepared, tested and found active, further modifications of these structures are still necessary. The sulphonamides thus produced by these modifications may prove to be more active and hence useful as antimicrobial agents. The active metabolite of the red azo dye known as Prontosil 7 does not possess any activity in vitro; however it metabolizes in vivo to give the active agent sulphanilamide 8; where it can interfere with the process of bacterial DNA synthesis, and act as potent antibacterial agent. Its synthesis involves the reaction of sulphonyl chlorides using indium catalysis⁶⁵. We synthesized new sulphonamides from benzene sulphonyl chloride using anhydrous acetone and dry pyridine. They are N-(4-methylpyridin-2-yl)benzene sulphonamide, N-(3-nitropyridin-2-yl)benzene sulphonamide, N-(3-hydroxypyridin-2-yl)benzene sulphonamide and etc.

The previous structures:

The new structure:

 

 

 

1. The objective of study is to synthesize new heteroaryyl sulphonamides and evaluate their

biological activities.

2. The specific objectives of this research work were to:
3. Synthesize some new sulphonamides with different substituents on the aromatic ring.
4. Synthesize some new sulphonamides with different substituents on the amino group.
5. Characterize them using spectrophotometric methods, namely, FT-IR, ¹H-NMR, and ¹³C-

NMR spectroscopy.

1. Carry out biological activitiy of their antimicrobial activities, acute toxicity, antimalarial activity, antioxidant activity, liver and kidney function test.

1.6       Justification of study

            The recent advances in the development of sulphonamides as drugs, the synthesis and biological activities of N-heteroaryl derivatives of benzene sulphonamides remain largely unknown. The need to synthesize new heteroaryl derivatives of benzene sulphonamides for activities of their antimicrobial activity, acute toxicity test, antimalaria activity, antioxidant activity, liver and kidney function test potentials motivated this work. Arylsulphonamide compounds were known to possess various biological activities⁶⁶; sulphonamides are synthetic antimicrobial agents which act as competitive inhibitors of the enzyme dihydropteroate synthetase. All the synthesized benzene sulphonamides have shown good activity against the tested microbes. A large number of sulphonamides derivatives have ultimately been reported to show substantial protease inhibitor properties. Some derivatives of sulphonamides are extensively used for gastrointestinal and urinary tract infections because of their ease of administration and non-interaction with defense mechanism of host. All these findings encouraged us to explore the synthesis of different N-substituted sulphonamides derived from o-anisidine with improved and different biological activity.

 

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