Browsing by Author "Karpoormath, Rajshekhar."

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Comparative chemistry of COA® herbal medicine and herbal extracts of azadirachta indica and carica papaya.
(2019) Nwabuife, Joshua Chukwufumnanya.; Manimbulu, Nlooto.; Karpoormath, Rajshekhar.
Natural products have indeed endowed man with a variety of efficacious benefit combinations which can be dated to origin of the universe. The essence of herbs in the mitigation of human indisposition cannot be overstressed. The plant kingdom is believed to be a dockyard of never-ending genesis of active compounds paramount for the prophylaxis and mitigation of countless communicable and non-communicable disease conditions of mankind. Orthodox therapeutic substances used for basic medical care necessity, in recent times, have caught the attention of researchers; the rationale for this may be explained by the increased use of chemically derived therapeutic agents having adverse effects and negative clinical outcomes. This has seen the good turn of people to natural products such as COA® herbal medicine produced in Ghana and used by people in South Africa. However, the phytochemistry of COA® herbal medicine may not be well known. This study was aimed to establish the differences and similarities of phytochemical compounds found in COA® herbal medicine and two of its constituent plants (Azadirachta indica and Carica papaya Linn.) collected in Cape Coast (Ghana), Durban and Port Shepstone (South Africa). Method An experimental study was conducted in the pharmaceutical chemistry laboratory, discipline of pharmaceutical sciences, School of Health Sciences and in the chemistry laboratory, School of Chemistry and Physics, University of KwaZulu – Natal. A phytochemical screening and Gas Chromatography–Mass Spectrometry (GC-MS) were carried out using hexane, ethanol, ethyl acetate and dichloromethane extracts to establish the similarities and disparities between the COA® herbal medicine and leaf extracts of Azadirachta indica and Carica papaya Linn. collected in Ghana and South Africa. The mass spectra of the compounds found in the analyzed extracts were matched with the National Institute of Standards and Technology (NIST) library. Results The results of the phytochemical screening revealed the presence of alkaloids, anthraquinones, flavonoids, saponins, tannins, terpenoids and steroids, cardiac glucosides. GC–MS results revealed the presence of common phytochemical compounds such as Phyto acetate, Octadecanoic acid, Pentadecanoic acid, Stigmast-5-en-3-ol, Stigmast-5,22-dien-3-ol, in COA® herbal medicine and leaf extracts of Azadirachta indica and Carica papaya Linn. collected in Ghana and South Africa. However, this study confirmed the differences in phytochemical compounds from leaf extracts of Azadirachta indica and Carica papaya Linn. collected in Ghana and South Africa. Conclusion This study found that there were similarities between COA® herbal medicine and leaf extracts of Azadirachta indica and Carica papaya Linn. However, differences in phytochemical compounds were observed between leaf extracts of Azadirachta indica and Carica papaya Linn. collected in Ghana and South Africa.
Cytochrome p450 monooxygenase cyp139 family involved in the synthesis of secondary metabolites in mycobacterial species.
(2019) Syed, Puleng Rosinah.; Karpoormath, Rajshekhar.
Tuberculosis (TB) is one of the top infectious diseases causing numerous human deaths in the world. Despite enormous efforts, the physiology of the causative agent, Mycobacterium tuberculosis, is still poorly understood. To contribute to better understanding the physiological capacity of these microbes, we have carried out extensive in silico analyses of the 1111 mycobacterial species genomes focusing on revealing the role of the orphan cytochrome P450 monooxygenase (CYP) CYP139 family. We have found that CYP139 members are present in 894 species belonging to three mycobacterial groups: M. tuberculosis complex (850-species), Mycobacterium avium complex (34-species), and non-tuberculosis mycobacteria (10-species), with all CYP139 members belonging to the subfamily “A”. CYP139 members have unique amino acid patterns at the CXG motif. Amino acid conservation analysis placed this family in the 8th among CYP families belonging to different biological domains and kingdoms. Biosynthetic gene cluster analyses have revealed that 92% of CYP139As might be associated with producing different secondary metabolites. Such enhanced secondary metabolic potentials with the involvement of CYP139A members might have provided mycobacterial species with advantageous traits in diverse niches competing with other microbial or viral agents, and might help these microbes infect hosts by interfering with the hosts’ metabolism and immune system.
Design and development of novel nanocomposite based electrochemical sensors for quantification of antimalarial drugs and early detection of malaria.
(2021) Nate, Zondi.; Karpoormath, Rajshekhar.
Malaria is still a major disease in sub-Saharan Africa and South-East Asia. This is despite different interventions by the World Health Organization (WHO) such as the use of insecticide-treated mosquito net, antimalarial drugs, indoor residual spraying, and rapid diagnostic tools. In 2018, the mortality rate due to malaria was estimated to be 405 000, with children under the age of 5 accounting for 67% of all malaria deaths. Malaria can be prevented and treated using different strategies as recommended by WHO. However, the lack of rapid diagnostic tools with good selectivity and sensitivity is still a challenge. Another problem is the high prevalence of counterfeit antimalarial drugs. These drugs are dominant in most African countries since the cost of medicine is high and some countries lack good quality control and verification processes. Therefore there is a need to develop rapid, low-cost, and portable analytical methods for the quantification of malaria and antimalarial drugs. This review focuses on the role of malaria biomarkers in diagnosis; Plasmodium falciparum Lactate Dehydrogenase (PfLDH), Plasmodium aldolase, Plasmodium falciparum Histidine-Rich Protein 2 (PfHRP2) and Plasmodium falciparum Glutamate dehydrogenase (PfGDH) and Hemozoin. Recent developments in nanomaterial-based electrochemical and colorimetric biosensors for malaria diagnosis are discussed. Also, electrochemical sensors for qualitative and quantitative analysis of different antimalarial compounds (Quinoline-related compounds, artemisinin derivatives, antifolates, and antibiotics), which have been approved by the World Health Organization are covered. Finally, the closing remarks and future perspectives of electrochemical sensors and biosensors conclude the review.
Design, synthesis and biological evaluation of antimicrobial agents: bromopyrrole-cinnamaldehyde hybrids.
(2018) Dlungele, Andile Princess.; Karpoormath, Rajshekhar.
Antimicrobial resistance threatens the effective prevention and treatment of an increasing range of Infections. The ongoing discovery of newer antimicrobial resistance has been a driving energy in the design, synthesis and development of newer antimicrobial agents. As a contribution to these efforts, we synthesized novel Bromopyrrole-Cinnamaldehyde Hybrids compounds. A series of fifteen Bromopyrrole-Cinnamaldehyde Hybrids molecules were synthesized by molecular hybridization approach. In vitro anti-mycobacterial activity of synthesized compounds was evaluated against Mycobacterium tuberculosis H37Rv strain. Among the series, 4(b-e) exhibited activity (MIC >20 μM; IC50 = >20 μM) furthermore the sythesised hybrids displayed promising activity against tested fungal strains, in particular for clinical isolate of C. neoformans with MIC values ranging from 12.5 – 25 μg/mL. All synthesized compounds were confirmed by melting point, FT-IR, 1H-NMR and 13C-NMR spectroscopy. The yield of these compounds obtained ranged from 40% to 80%.
Design, synthesis and biological evaluation of novel thiadiazoline-thiazolone hybrids as kinase inhibitors.
(2017) Khathi, Samukelisiwe Pretty.; Karpoormath, Rajshekhar.
Cancer is a leading cause of death globally, and it was responsible for 8.8 million deaths in 2015. It is predicted that there will be 22 million new cancer cases by 2030 worldwide. Approximately, 70% of deaths from cancer occur in low- and middle-income countries. Furthermore, breast cancer is the second most common cancer among South African women and is reported to affect 1 in every 26 women. The social and economic burdens associated with cancers are severe at national and international levels hence, there is an urgent need for the development of more effective cancer therapeutics. To accomplish this aspect, in this study, thiadiazole-thiazolone (TDT) hybrids were developed as dual inhibitors of cyclindependent kinase (CDK) and kinesin spindle protein (KSP), respectively. Twenty-two novel TDT hybrid compounds (8a-v) were synthesized using multistep organic synthesis and were characterized using thin layer chromatography (TLC), infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H and 13C NMR), and high-resolution mass spectrometry (HR-MS). All the compounds (8a-v) were screened for their potential in vitro inhibition of validated anticancer drug targets (CDK, Abl and KSP) and cancer cell lines (MCF-7 and K562). Results obtained from these evaluations suggested that the synthesized compounds were potent inhibitors of CDK and KSP thus confirming the dual mode of action. Amongst, 8h was identified as the most potent compound with an IC50 value of 3.1 µM against CDK2 enzyme and exhibited good cytotoxicity (GI50 = 6.25 µM) against the tested cancer cell lines (MCF-7 and K-562). A brief structure-activity relationship (SAR) analysis indicated that 2- chloro and 4-nitro substituents on the phenyl ring of the thiazolone motif contributed significantly to the inhibition of both of the anticancer drug targets (CDK and KSP). An in silico molecular docking study using the crystal structures of the target enzymes (CDK-2 and KSP) further supported the SAR and extrapolated the importance of crucial molecular interactions in influencing the enzyme inhibitory activities
Design, synthesis and pharmacological evaluation of novel fused pyrimidine analogues as anticancer agents.
(2018) Cherukupalli, Srinivasulu.; Karpoormath, Rajshekhar.
Cancer is a multifaceted disease considered as the most serious health burden all over the world. Due to existing of limited anticancer drugs and detrimental side effects, the anticancer research has been challenging. An investigation on identifying novel potential drugs is highly required to treat this serious abnormal cell growth. Advanced potential anticancer drug entrants are crucially required to combat the drawbacks linked with current drugs or line of therapies. Extensive investigations are being carried out on synthetic manipulations of heterocyclic aromatic compounds (purines) for developing efficient and potent anticancer drugs. Besides, these manipulations also offer effective leads for further optimization. Therefore, this project is an effort in detecting a novel and potent anticancer leads based on bioisostere of purines called pyrazolopyrimidines. In this research project we have performed an comprehensive literature survey of structural isomers of pyrazolopyrimidines (pyrazolo[1,5-a]pyrimidine and pyrazolo[4,3-d]pyrimidine) for their synthetic approaches and biological activities with special emphasis on structure-activity relationship (SAR) studies. These SAR studies prompted us to implement the observed studies on one of the structural isomer of pyrazolopyrimidine called pyrazolo[3,4-d]pyrimidine. And further, we have synthesized some novel series of pyrazolo[3,4-d]pyrimidine derivatives with various substituents at C-4 and C-6 positions of the scaffold. A total 71 compounds comprising of phenethyl and pentane hybrids (7-43, Chapter 4), benzoyl hybrids (5a-5h, 6a-6d and 7a-7c, Chapter 5) and lastly phenylcarbamoyl acetamide hybrids (9a-9s, Chapter 6) have been synthesized by molecular hybridization approach as outlined in schemes of respective chapters. The completion of reaction and the purity of novel synthesized compounds were confirmed by chromatographic analysis. All the newly synthesized compounds displayed acceptable analysis for their anticipated structures, which were established based on physicochemical and spectral data (IR, 1 H NMR, 13C NMR and HRMS). All synthesized compounds were primarily evaluated for their in vitro anticancer activities at Laboratory of Growth Regulators, Centre of the Region Hana for Biotechnological and Agricultural Research, Palacky University & Institute of Experimental Botany ASCR, Slechtitelu 27, 78371 Olomouc, Czech Republic. From the systematic analysis of anticancer activity, results obtained following key observations were made. i. Structural isomers of fused pyrimidines have been looked upon for molecular changes in emerging drug like candidates. Pyrazolopyrimidine is a bioisostere of purines has acquired considerable importance due to its diverse, facile and general synthetic methodologies with great medicinal importance. Several analogs of this scaffold have emerged as a promising leads in the design of some novel pharmacologically active compounds with enhanced iii metabolic, pharmacokinetic and pharmacological profiles, representing that there is plenty scope for considering pyrazolopyrimidine as a structural framework for evolving effective leads. ii. Chapter 4: From the 37 novel phenethyl and alkyl pentane pyrazolo[3,4-d]pyrimidine derivatives synthesized and evaluated for CDK2/Cyclin E, Abl kinase inhibitory activity and anti-proliferative activity against K-562 (chronic myelogeneous leukemia) and MCF7 (breast adenocarcinoma) cell lines. From the tested results, compounds 11 (CDK: IC50 = 5.1 µM; Abl: ˃12.5 µM), 8 (CDK: IC50 = 7.8 µM; Abl: ˃25 µM) and 36 (CDK: IC50 = 8.8 µM; Abl: >25 µM) exhibited significant inhibitory activity. Further from this series, most of the synthesized compounds indicated prominent anti-proliferative effects with IC50 value ranging from 19.2 µM to 27.4 µM. Incorporation of monosubstituted phenyl groups at C-4 of the pyrazolo[3,4-d]pyrimidine nucleus had favored for most prominent anticancer activity. iii. Chapter 5: Among the 15 novel benzoyl hybrids synthesized and evaluated, compounds 5a and 6c displayed (CDK2: IC50 = 8.8 µM, 6.8 µM) commendable inhibitory activity and notable anti-proliferative activity ranging from 18.9 µM to 89.3 µM). Presence of heteroatom containing bicyclic moieties at C-4 of the nucleus enhanced both inhibitory and anti-proliferative activity. iv. Chapter 6: Of the 19 novel phenylcarbamoyl acetamide hybrids synthesized and tested, compounds 9a, 9c, 9g, 9m and 9p showed moderate enzymatic inhibitory activity with an IC50 value ˃12.5 µM against both CDK2 and Abl kinases while, remaining compounds of this series could not generate IC50 values due to solubility limit (IC50 = ˃25 µM to ˃100 µM).
Design, synthesis and spectral characterization of quinazoline and benzoxazine derivatives as novel DNA gyrase inhibitors.
(2020) Kushwaha, Narva Deshwar.; Karpoormath, Rajshekhar.
Tuberculosis (TB) has remained one of the leading causes of the death worldwide and recently surpassed HIV/AIDS as lethal disease caused by a single infectious agent. Further, development of resistance against frontline anti-tubercular drugs has worsened the existing alarming condition. Therefore, there is an urgent need to develop novel, more effective, inexpensive and accessible antitubercular agents possessing broad spectrum of potency short duration of drug regimen, less side effects, which can counter the drug resistant TB and reduce the burden on the society. Global scientific communities and pharmaceutical industries are aggressively involved in research to develop a novel broad spectrum anti-tubercular agent to address this rising threat to human kind. In continuation of our work, focused in developing new anti-TB agents, we have attempted to develop some potential quinazoline based DNA gyrase and topoisomerase IV inhibitors as potential anti-tubercular agents. In addition, we have developed novel green and efficient catalyst-free, mild one-pot tandem synthetic strategy to synthesize benzoxazine derivatives, that can be further exploited as building blocks for the synthesis of multifaceted molecular structures, especially for anti-tuberculosis agents. Chapter 1 gives a brief overview on drug discovery and medicinal chemistry, history of antibiotic expansion, development of resistance in bacteria, history of anti-TB drugs discovery, line of treatment for TB, anti-tubercular drugs and their specific targets, classification of TB drugs, DNA gyrase and topoisomerase IV as a key target for anti-tubercular agents, marketed drugs and recently reported DNA gyrase inhibitors, importance of benzoxazine and quinazoline scaffold as well as significance of fluorine containing heterocycles in medicinal chemistry. Chapter 2 describes, the development of a novel methodology which is green, efficient catalyst-free and is a mild one-pot, multicomponent synthetic strategy to construct substituted 3,4-dihydro-2H-benzo[b][1,4]oxazine. The reaction proceeds via in-situ formation of Schiffbase followed by base mediated alkylation with phenacyl bromide/substituted phenacyl bromide, finally leading to intramolecular cyclization to give a mixture of diastereomers with excellent diastereoselectivity (up to dr = 99:1), which were isolated as single diastereomer in moderate to excellent yields (41-92%). Besides, this new versatile methodology provides a wide scope for the synthesis of different functionally substituted benzoxazine scaffolds and can be further exploited as building blocks for the synthesis of multifaceted molecular structures, especially for pharmaceutical applications. In Chapter 3, 15 novel fluorinated quinazoline derivatives have been synthesized and characterized with Infrared (IR) and Nuclear Magnetic Resonance (NMR) spectroscopic methods. This chapter also describes the influence of various substituents on the core scaffold (Fluorinated quinazoline) on its molecular conformations, intermolecular interactions and on the photoluminescent properties. Hirshfeld surfaces was used to investigate the structure-directing effects of functional groups in controlling their solid-state behaviour. In Chapter 4, a total 21 novel quinazoline derivatives (10a-q and 17a-c) were synthesized in good to moderate yields. The synthesized compounds were well-characterized by spectroscopic studies (IR and NMR) and evaluated for their preliminary in vitro screening against Mycobacterium tuberculosis H37Rv strain, which was conducted at TB Discovery Research, Infectious Disease Research Institute (IDRI), USA. The only notable % zone of inhibition was observed against Mycobacterium tuberculosis strain H37Rv for compounds 10m which showed 33% inhibition after 24 h incubation which can be considered for further study which includes MIC, MBC etc. In Chapter 5, total 23 novel N/O-methylated quinazoline derivatives (10a-o, 16a-d and 16aaad) were synthesized in good to moderate yields. All synthesized compounds were wellcharacterized by spectroscopic studies (IR and NMR) and evaluated for preliminary in-vitro screening for anti-mycobacterium activity at 20 µM concentration against Mycobacterium tuberculosis H37Rv strain at TB Discovery Research, Infectious Disease Research Institute (IDRI), USA. The % zone of inhibition for compounds 16a, against Mycobacterium tuberculosis strain H37Rv was found to be 34% after 24 h incubation. Chapter 6 describes, the development of novel quinazoline based DNA gyrase inhibitors as potential antibacterial agents. Bacterial type II topoisomerase (DNA gyrase and topoisomerase IV) control the topological state of DNA during replication and are validated targets for antibacterial agents. Type II topoisomerase is essential in all bacteria. It is also present in eukaryotic cells but unlike the prokaryotic enzymes eukaryotic topoisomerase II is homodimeric, this difference in structure makes highly attractive targets in antibacterial drug discovery. Fluoroquinolones are an example of very active gyrase-based drugs, but the rise in bacterial resistance to these agents alarm the risk. We have replaced the central core quinolone with quinazoline ring and synthesized 22 derivatives and evaluated against DNA gyrase and topoisomerase IV enzyme of Escherichia coli. The most potent compound (10l) displayed balanced IC50 value of 0.49 and 13.22 μM for DNA Gyrase and topoisomerase IV of Escherichia coli respectively. This result is intresting for the further studies as it showed promising well-balanced duel inhibiton in the low micromolar range against DNA gyrase and topoisomerase IV in E. coli.
Design, synthesis, and biological evaluation of novel pentacyclo undecane derived peptides/peptoids as potential HIV-1 protease inhibitors.
(2012) Karpoormath, Rajshekhar.; Kindness, Andrew.
This study reports a series of promising and structurally diverse potential HIV-1 protease inhibitors. Human Immunodeficiency Virus (HIV) is the causative agent of Acquired Immune Deficiency Syndrome (AIDS). HIV infection disrupts the immune system and makes the body susceptible to opportunistic infections. If untreated, AIDS is generally fatal. Today, AIDS has become a long lasting pandemic. According to the World Health Organization (WHO) and Joint United Nations Program (UNAIDS-2009) report, it is estimated that 33.3 million men, women and children worldwide are infected with HIV. This situation is steadily deteriorating in some parts of the world compared to the previous years. One of the major drawbacks associated with the currently FDA-approved anti-HIV drugs are severe side effects, toxicities, high dosage and high treatment cost. Thus, an urgent need for new drugs to combat HIV is apparent. In the first part of the study, research efforts were focused to synthesize potent pentacycloundecane (PCU) derived peptide and peptoids as protease inhibitors. It is proposed that these inhibitors bind to wild type C-South African HIV protease (C-SA) catalytic site via a non-cleavable or non-hydrolysable cyclic ether bond for the first polycyclic cage compound and via a dihydroxylethelene type functional group for the second cage compound. The desired compounds were synthesized by coupling of the peptides and peptoids to the PCU derived cage. Second part of the study involves, biological evaluation against wild type C-SA enzyme and characterization of the synthesized compounds by Nuclear Magnetic Resonances (NMR). All the synthesized novel compounds were evaluated against wild type C-SA enzyme for their ability to inhibit 50% of the enzyme’s activity (IC50). Some of the compounds reported herein showed promising activity by inhibiting the enzyme activity at concentrations of less than 0.6 nM. 2D NMR investigations employing a new Efficient Adiabatic Symmetrized Rotating Overhauser Effect Spectroscopy (ROESY / NOESY) technique enabled the attainment of vital information about the 3D structure of these small linear peptides and peptoids in solution. The activity could be related to conformations induced by the PCU moiety on the coupled peptide side chain. Further quantum mechanics/molecular mechanics/molecular dynamics (QM/MM/MD) simulations were carried out to confirm the observed NMR experimental results. Docking studies were performed for the synthesized compounds. Binding energies obtained from the docking calculations were then used to further validate the experimental IC50 results. These experimental and theoretical methods provided valuable insight into the interaction mode of these cage peptide and peptoids inhibitors with the enzyme.
Designed, synthesis and antibacterial evolution of piperazine hybrids.
(2023) Girase, Pankaj Sanjay.; Karpoormath, Rajshekhar.
Piperazine is a kind of azacycloalkane that has two nitrogen atoms at1-4 places on a six-membered ring. It is well known that molecules with the piperazine ring, a key component of the N-heterocyclicfamily of bioactive natural products, are often prevalent in biologically active substances. There are many antitumor, antibacterial, antiinflammatory, antipsychotic, antifungal, and anti-diabetic compounds based on the piperazine scaffold, which has been recognized as an active structure in drug discovery. Piperazine hybrids with different moieties such as isoniazid, coumarin, benzothiazinones, isoquinoline, triazole,pyrrole, and oxazolidinone showed good activity against mycobacterium tuberculosis and microbial strains. In this thesis we have demonstrated the synthesis of piperazine hybrid with hydrazides, hydrazines, and coumarines and tested their activity against mycobacterium tuberculosis, gram positive and gram negative microbial strains. In Chapter 2, we have covered topics related to the analogues of piperazine that have anti-tubercular efficacy. This chapter we have published as a review article in European Journal of Medicinal Chemistry. In this review, we have made a concerted effort to trace the development of anti-mycobacterial compounds during the past 50 years (1971-2019), focusing on instances where piperazine has been utilized as a key building block. In depth discussion of the design, rationale, and structure-activity relationship (SAR) of the reported potent piperazine-based anti-TB molecules will help medicinal chemists fill in the blanks, capitalize on the reported strategies, and create more effective, selective, and less hazardous anti-mycobacterial drugs. In chapter 3, we have developed and synthesized a new class of hybrids between phenylpiperazine and hydrazides (c1-c15). During the synthesis of phenyl piperazines, the formylation of piperazine was observed, a phenomenon on which we have developed a different methodology discussed in chapter 5. All of the derivatives have been tested in vitro against H37Rv, a strain of mycobacterium. In addition, we have analysed the zone of inhibition against eight different bacterial strains, including both gram-positive (methicillin resistant staphylococcus aureus (MRSA), Streptococcus pyrogens, Bacillus subtilis, Enterococcus faecium, and Staphylococcus aureus), and gram-negative (Enterobacter hormaechei, Pseudomonas aeruginosa, and Escherichia coli) bacteria. Among the derivatives tested, only compound c8 showed action against the mycobacterium strain H37Rv (MIC value of 0.39-0.78 g/ml). No zone of inhibition was seen for any of the microbiological strains when exposed to any of the synthesized compounds. The hybrids between phenylpiperazine sulphonamide and phenyl hydrazide (E1-E6) and phenylpiperazine sulphonamide and phenyl hydrazine (F7-F19) were proposed and synthesized in chapter 4. All substances were evaluated against mycobacterium tuberculosis, five gram-positive and three gram-negative bacterial strains in vitro. Derivatives E1 and E2 with an isoniazid moiety were the most effective in inhibiting the growth of the H37Rv strain of tuberculosis, with an IC50 value of 3.125 M. Of the derivatives tested, F10 showed significant action against the gram-positive bacteria Enterococcus faecium (7.81 μg/mL), whereas the others (E2, E6, F7, F9, F14) were only moderately active (250-62.5 μg/mL). Using a the molecular hybridization strategy, we were enabled to create novel analogues of coumarin-(phenylsulfonyl)piperazine and 4-methyl coumarin-(phenylsulfonyl)piperazine in chapter 5.All synthesised compounds were evaluated for their in vitro anti-mycobacterial and antimicrobial activity against H37Rvand a variety of antimicrobial gram-positive and gram-negative strains.The Compounds 6G, 6H, 10D and 10E displayed moderate inhibition against gram positive and gram negative strains with MIC values in the range of 62.5-250 (table 1) against MRSA, Bacillus subtilis, and Enterococcus faecium, and gram negative strains Enterobacter hormaechei, Pseudomonas aeruginosa, and Escherichia coli.In addition, the Structure-Activity Relationship (SAR) analysis showed that phenyl ring substituents could enhance antibacterial activity. Chapter 6 came from the process of synthesizing phenyl piperazine in chapter 1. This chapter disclosed a method for efficient synthesis of transamidation in the presence of Iodine and NH2OH.HCl which published in Chemistry Select. This method is efficient for a broad range of primary, secondary, and tertiary amides, and it enables the formylation, acylation, and benzoylation of a number of different amines. The key benefits of the present technique are that it is easy to follow, quick, does not need a metal catalyst, uses a starting material that is inexpensive, and has a low effect on the environment when the synthesis process is carried out. All of the chapters in this thesis are written in thesis by publication style, rather than the conventional style.
Nanoencapsulation of novel pyrazolone-based compounds to enhance solubility and biological activity.
(2022) Igbokwe, Nkeiruka Nkeonyere.; Faya, Andile Kennedy Mbuso.; Karpoormath, Rajshekhar.
The biological activity of pyrazolone-based derivatives has been thoroughly documented; nonetheless, low stability and water solubility are their main drawbacks, preventing effective translation to clinical application. Based on this, two previously reported weakly soluble pyrazolone-based compounds, PBC-301 and PBC-302, were encapsulated using PLGA: poloxamer complex to improve their solubility and further examine the influence of solubility augmentation on their biological activities. We first developed and validated a simple, accurate RP HPLC-PDA method for detecting, measuring, and standardising the compounds in nanoformulations to achieve this wide goal. Efficient separation and quantification were carried out using Shim-pack GIST C18 (5 𝜇m 150 × 4.6 mm) column, maintained at 25 ℃ with isocratic elution using acetonitrile and acidified water (0.1% Trifluoracetic acid) (75:25 v/v) at 0.5 mL/min flow rate. The injection volume was 20 𝜇L, and eluents were detected at 333 nm at a retention time of 4.82 mins. Method validation was done following ICH guidelines. Results demonstrated that the method is specific, precise, and accurate within the recommended limits. The method showed good linearity with a 0.9994 correlation coefficient over a concentration range of 2.5-50 𝜇g/ml. The method efficiently detected and quantified the novel pyrazolone compound in the nanosuspension. The obtained nanoformulations PBC-PLGA 301 and PBC-PLGA 302 were characterised using various in vitro techniques. Size, PDI and ZP of the optimised nanoformulations were 166.6 ± 7.12 nm, 0.129 ± 0.042, -14.14 ± 2.90 mV for PBC-PLGA 301 and 192.5 ± 1.08 nm, 0.132 ± 0.025, -10.77 ± 1.515 mV for PBC-PLGA 302 with the encapsulation efficiency being 84.20 ± 0.930 and 81.5 ± 2.051, respectively. The compound release from the nanovesicles followed a sustained release pattern, with PBC-PLGA 301 and PBC-PLGA 302 attaining a cumulative release of approximately 37% and 53% in 48 hours. The biological activity assays showed a better-enhanced activity with the nanoformulations compared to the non-encapsulated PBC 301 and PBC-302. In vitro antibacterial activity revealed that the compound-loaded nanovesicles have better activity against the two gram-positive bacteria S. aureus and Methicillin-resistant S. aureus compared to the standard drug vancomycin and the non-encapsulated compound. On the other, the cell penetration assay further revealed that the compound-loaded nanovesicles achieved greater than 90% propidium iodide penetration (translating to cell death) at the reported MIC well for S. aureus while showing 86% and 89% cell penetration for Methicillin-resistant S. aureus. Also, the nanoformulations showed improved radical scavenging activity in a concentration-dependent manner, with PBC-PLGA 301 exhibiting the best antioxidant activity against DPPH, FRAP and nitric oxide compared to the standard antioxidant-gallic acid and the non-encapsulated compounds. In conclusion, the aqueous solubility of the two pyrazolone compounds, PBC-301 and PBC-302, was greatly enhanced by their encapsulation into a nanosystem, resulting in improved biological activities. Therefore, the nanoformulations of the pyrazolone-based derivatives can be exploited as potential pharmaceutical agents to fight bacterial infections and other diseases triggered by oxidative stress, cancer, and hepatic and vascular diseases. The data from this study has resulted in two first-authored research publications.
Novel quinolone substituted urea and thiourea derivatives as anti-microbial and anti-cancer agents : design, synthesis and biological screening.
(2015) Faya, Mbuso.; Karpoormath, Rajshekhar.
Abstract available in PDF file.
Novel series of dehydrozingerone inspired potential antimycobacterial agents: design, synthesis, spectral studies and in vitro biological evaluation.
(2016) Hampannavar, Girish Appasaheb.; Karpoormath, Rajshekhar.
Tuberculosis (TB) is a key health burden globally. With the emergence of resistance issue, the antitubercular research has been challenging. Novel effective drugs are immediately required to treat this serious epidemic disease. Innovative potential antitubercular drug candidates are momentously required to combat the disadvantages linked with existing drugs or line of treatments. Synthetic manipulations of natural sources are being extensively investigated worldwide for developing potent and efficient drugs. Besides, these manipulations also offer effective leads for further optimization. Therefore, this project is an effort in identifying a novel and effective antitubercular leads based on natural product model dehydrozingerone (DZG), a curcumin degradant. In this project we have performed an extensive literature survey of DZG for its known biological activities. And further, we have synthesized some novel series of DZG fused heterocyclic compounds with three different 5 membered heterocyclic scaffolds namely, thiazole, thiazolidon- 4-one and pyrazole. A total of 53 compounds comprising of styryl hydrazine thiazole hybrids (6ao, Chapter 3), styryl hydrazine thiazolidin-4-one hybrids (7a-d, 10a-l and 13a-b, Chapter 4) and lastly styryl fused pyrazole derivatives of acid hydrazides, semicarbazone and thiosemicarbazones (8a-i, 11a-h and 14a-c, Chapter 5) have been synthesized by versatile synthetic routes as outlined in schemes of respective chapters. The completion of reaction and the purity of synthesized compounds were established by chromatographic analysis. All the newly synthesized compounds displayed acceptable analysis for their anticipated structures, which were established based on physicochemical and spectral data (IR, 1H NMR, 13C NMR and HRMS). These newly synthesized compounds were primarily evaluated for their in vitro antimycobacterial activities at Infectious Disease Research Institute (IDRI) within the National Institute of Allergy and Infectious Diseases (NIAID) screening program, Bethesda, USA or Department of Microbiology, Inkosi Albert Luthuli Hospital, Durban, South Africa. From the systematic analysis of antimycobacterial activity results obtained following key observations were made. i. Degradants of curcumin have been looked upon for molecular variations in developing diverse scaffolds. DZG is an imperative scaffold and its numerous analogs have emerged as a promising leads in the design and development of some novel medicinally active compounds with improved metabolic, pharmacokinetic and pharmacological profiles, indicating that there is much scope for considering DZG as a structural framework for developing effective leads. ii. Chapter 3: Of the fifteen novel styryl hydrazine thiazole derivatives synthesized and tested, compound 6o exhibited significant antimycobacterial activity (H37Rv; MIC = 1.5 μM; IC50 = 0.48 μM) along with bactericidal (MBC = 12 μM) and intracellular antimycobacterial activities (IC50 = < 0.098 μM). Furthermore, 6o displayed prominent antimycobacterial activity under hypoxic (MIC = 46 μM) and normal oxygen (MIC = 0.28 μM) conditions along with anti-mycobacterial efficiency against isoniazid (MIC = 3.2 μM for INH-R1; 1.5 μM for INH-R2) and rifampicin (MIC = 2.2 μM for RIF-R1; 6.3 μM for RIF-R2) resistant strains of Mycobacterium tuberculosis. Presence of electron donating groups on the phenyl ring of thiazole moiety had positive correlation for antimycobacterial activity. iii. Chapter 4: From the eighteen novel styryl hydrazine thiazolidin-4-one hybrids derivatives synthesized and tested, Compounds 7a (MIC = 110 μM; IC50 = 67 μM), 7c (MIC = 120 μM; IC50 = 66 μM) and 10g (MIC = 100 μM; IC50 = 100 μM) exhibited noteworthy antimycobacterial activity. Further, the title compounds displayed least cytotoxic effects against a mammalian Vero cell determined using MTT assay. iv. Chapter 5: Among the twenty novel styryl pyrazolo carbazone derivatives synthesized and tested, Compounds 8a, 8c, 8d, 8g, 8h, 8i and 11f showed reasonable antibacterial activity (MIC = 50 μg/mL) against B. subtilis, compound 11a demonstrated noteworthy activity towards P. aeruginosa (MIC = 25 μg/mL). Further, compounds 8a, 8d, 8e, 8f, 8i, and 11h showed good to moderate antifungal activity ranging from 25 to 50 μg/mL towards C. neoformans (MIC = 25 μg/mL) and C. albicans (MIC = 50 μg/mL). Besides, compound 8a, comprising of isonicotinoyl hydrazide portion displayed remarkable antitubercular activity (MIC = 0.78 μg/mL) against H37Rv. Substituted urea derivatives, 14a-c and 11d also exhibited encouraging activity (MIC = 12.5 and 25 μg/mL, respectively) whereas, derivative with carbothioamide portion 11a, (MIC = 0.78 μg/mL) illustrated significant activity against H37Rv. Moreover, some of the tested compounds showed reasonable activity against MDR (multi drug resistant) and MOTT (mycobacteria other that tuberculosis) strains.
A simple yet novel strategies for the synthesis of pharmacologically versatile benzoxazole and benzothiazole scaffolds via transamidation.
(2022) Kumar, Vishal.; Karpoormath, Rajshekhar.; Singh, Parvesh.
Transamidation is a popular way for amide transformation from another amide despite conventional amide bond formation methods. Acid and acid chloride were utilised as starting ingredients in previous procedures. Transamidation has shifted the perspective of researchers on amide synthesis. Nowadays, many methodologies have recently come to light for amide transformation, using non-metal and metalmediated techniques. On the other hand, a few approaches involving amide bond activators have been reported. Moreover, N-Boc, Tosyl, and Mesyl groups are commonly utilised as amide bond activators. As a result, many amides transformations have been synthesised and published in the literature over the last few decades. Based on previous research, we have attempted to develop cost-effective and novel techniques of transamidation for unactivated amides, which could serve as a potential alternative to synthesising amide bond containing compounds from lab to plant scale. We also demonstrated a novel approach for synthesising 2-substituted benzoxazole/benzothiazole compounds using this transformation. The history and development of unactivated amides transformation are briefly described in Chapter 2. This chapter also discusses different transamidation methods for primary, secondary, and tertiary unactivated amides that are transformed into other amides without the need for an amide bond activator. The development of a novel green, efficient catalyst-free, one-pot synthetic methodology to synthesise amides is described in Chapter 3. Under the optimisation investigations, the effects of various acids, solvents, temperatures, and time intervals were also described. The reaction was catalysed by hydrochloride, which activated the carbonyl bond, and then attacked the carbonyl carbon with an additive amine as a nucleophile. Finally, the amine as a byproduct is removed, resulting in the desired converted amide. Furthermore, this new transamidation process allows for a wide range of amide types, including primary, secondary, and tertiary. This approach also works with a variety of primary and secondary amines, including aliphatic and bulky, hetero-aromatic substituted amines. To continue the work begun in Chapter 4, we develop a new solvent-free and metal-free method for synthesising 2-substituted benzoxazole and benzothiazole in Chapter 4. In this approach, we increase the temperature and employ substituted 2-aminophenols or 2-aminothiophenols instead of amines. To lead the annulation product, the oxygen or sulphur atom of phenol or thiophenol attacks the carbonyl carbon of the transformed amide group. Furthermore, this technique works well with a variety of substituted 2-aminophenols. Additionally, the amide scope for this reaction is quite broad. Chapter 5 describes the development of a new method for the transamidation of aliphatic amides using CuCl2 as a catalyst. The effects of various catalysts and Lewis acids and the effect of different solvents were explained. Moreover, the annulated substituted 2-benzoxazole and 2-benzothiazole derivatives obtain in the case of 2-aminophenol and 2-aminothiophenol. Besides, this new versatile methodology provides a wide substrate scope for the synthesis of different functionally substituted amides and 1,3- benzoxazole scaffolds. It can be further exploited as building blocks for the synthesis of pharmaceutical drugs.
Synthesis and antimicrobial evaluation of novel 2,4-dihydro-3h-pyrazol-3-one hybrids: a new class of antibiotics.
(2019) Jain, Kavita.; Karpoormath, Rajshekhar.
The rise in multidrug resistance (MDR) pathogenic microbes has emerged as a critical global health burden. To address this problem, the scientific community and Pharmaceutical industries worldwide are focused in developing newer, safer and cost-effective antimicrobial agents. Design and development of potential antimicrobial agents has been one of the focus areas of the Synthetic and Medicinal Chemistry Research Group (SMCRG), UKZN. In continuation of the ongoing research in SMCRG and the need to discover newer antimicrobials, I envisaged to synthesize novel antimicrobial agents containing 2,4-Dihydro-3H-pyrazol-3-one (pyrazolone) as a core pharmacophoric moiety. Pyrazolones are versatile heterocyclic building blocks and is a core scaffold in several marketed drugs such as for analgesic and antipyretic (phenazone, metamizole, propyphenazon, and remifenazone); neuroprotective agent (edaravon); antispasmodic (dipyron); anti-inflammatory agents (famprofazone, phenylbutazone, and remifenazone) and more recently there have been several reports on the pyrazolone analogs as potential antimicrobial agents. In this research work I have synthesized a series of potential pyrazolone hybrids containing substituted 1,3,4-thiadiazole, thiazolidinone, triazole, oximes, and chalcones as antimicrobial agents (Figure 1). The work in this thesis is divided into 7 chapters:
Synthesis and antimicrobial evaluation of novel 2,4-dihydro-3h-pyrazol-3-one hybrids: a new class of antibiotics.
(2019) Jain, Kavita.; Karpoormath, Rajshekhar.
ABSTRACT The rise in multidrug resistance (MDR) pathogenic microbes has emerged as a critical global health burden. To address this problem, the scientific community and Pharmaceutical industries worldwide are focused in developing newer, safer and cost-effective antimicrobial agents. Design and development of potential antimicrobial agents has been one of the focus areas of the Synthetic and Medicinal Chemistry Research Group (SMCRG), UKZN. In continuation of the ongoing research in SMCRG and the need to discover newer antimicrobials, I envisaged to synthesize novel antimicrobial agents containing 2,4-Dihydro-3H-pyrazol-3-one (pyrazolone) as a core pharmacophoric moiety. Pyrazolones are versatile heterocyclic building blocks and is a core scaffold in several marketed drugs such as for analgesic and antipyretic (phenazone, metamizole, propyphenazon, and remifenazone); neuroprotective agent (edaravon); antispasmodic (dipyron); anti-inflammatory agents (famprofazone, phenylbutazone, and remifenazone) and more recently there have been several reports on the pyrazolone analogs as potential antimicrobial agents. In this research work I have synthesized a series of potential pyrazolone hybrids containing substituted 1,3,4-thiadiazole, thiazolidinone, triazole, oximes, and chalcones as antimicrobial agents (Figure 1). The work in this thesis is divided into 7 chapters.
Synthesis and biological evaluation of dihydropyrimidinone derivatives as a promising antimicrobial agents.
Muzenda, Wadzanai Janet.; Karpoormath, Rajshekhar.
Abstract available in PDF file.
Synthesis, characterization and application of novel composite nano-materials for the electrochemical detection of MRSA and related drugs.
(2020) Gill, Atal Anudeep Singh.; Karpoormath, Rajshekhar.; Thapliyal, Neeta Bachheti.
This thesis reports the development of electroanalytical methods applicable for detection of MRSA and selected antibacterial drugs; vancomycin and ciprofloxacin. The detection techniques used to carryout all electrochemical measurements involved Ag/AgCl (3 M KCl)) as reference electrode, platinum wire as the counter electrode and the glassy carbon electrode (GCE) as the working electrode. Firstly, to carry out the detection of vancomycin as single shot detection assay comprising of poly acrylic acid modied copper tricarboxylic acid based metal organic framework was employed. Cyclic voltammetry was used to carry out the highly sensitive detection of vancomycin. Ciprofloxacin was detected by modification of the GCE by beta cyclodextrin modified silver nanoparticles (Ag-β-CD/GCE) and by modifying another electrode with poly(phenol red)/reduced graphene oxide (rGO/PPR/GCE). Differential pulse voltammetry (DPV) was used to carry out the detection of the drug in various analytes such as animal blood serum, urine and domestic waste water samples. Finally, the electrode was modified with copperbeta-cyclodextrin-graphene oxide composite conjugated with vancomycin to act as a thernostic tool for detection and treatment of MRSA bacterial strains. DPV and impedance spectroscopy was used to carry out optimization and further the detection of MRSA. The designed sensors provided good sensitivity and low LOD for detection of the respective analytes with good specificity. Thus, the present study demonstrates a promising and alternative approach for clinical analysis and quality control of vancomycin and ciprofloxacin.
Synthesis, characterization and application of novel nano-materials for the electrochemical determination of antimalarial drugs.
(2019) Chiwunze, Tirivashe Elton.; Karpoormath, Rajshekhar.
ABSTRACT This thesis reports the development of electroanalytical methods applicable for determination of selected antimalarial drugs; primaquine, mefloquine and amodiaquine. The electrochemical behaviour of the drugs were carried out using three differently modified glassy carbon electrodes (GCE) as working electrodes. First working electrode was modified using synthesized gold nano-urchins (AuNU/GCE) and was used for the determination of mefloquine and primaquine separately. The second and third working electrodes were both used for the quantification of amodiaquine and were modified using the following composites; multi-walled carbon nanotubes with poly(methyl orange) (MWCNT/PMO/GCE) and gold nanoparticles decorated graphene oxide with poly-cysteamine (rGO-AuNP/Poly-Cyst/GCE). All measurements were carried out with a Ag/AgCl (3 M KCl)) reference using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The designed sensors showed enhanced voltammetric responses and very low limits of detection which are attributed to the high surface area and high conductivity of the nanomaterials. The proposed sensors also demonstrated practical utility in quantification of the antimalarial drug in pharmaceutical formulations and human urine sample. Thus, the present study demonstrates a promising and alternative approach for clinical analysis and quality control of primaquine, mefloquine and amodiaquine.