INTRODUCTION:
Azomethine are ketone- or aldehyde- like compounds in which the carbonyl group is substituted by an imine or azomethine group1. Azomethine are formed when primary amine react with carbonyl compounds2-5 and were first described by Hugo Schiff in 18646. The formation of Azomethine generally takes place under acid or base catalysis or by heat. The Azomethine are typically crystalline solids, which are weakly basic but at least some form insoluble salts with strong acids3. Nowadays, Azomethine are commonly used as intermediates for the synthesis of amino acids or as ligands for synthesis of metal complexes with a variety of structures3. They encompass various therapeutically effective applications in the field of medicinal chemistry4.
Moreover, Azomethine have been shown antifungal7, antibacterial8,9, antimicrobial10-13, antiproliferative, anti-inflammatory14-16, antiviral, UTI activity, and antipyretic properties1,6. Like M. tuberculosis, gram-negative bacteria are also evolving as drug resistance strains particularly Extended Spectrum-β-lactamase (ESBL) and Metallo-β-lactamase (MBL) producing organisms. Repeated or lengthy courses of antibiotics, frequent use of catheters, indwelling devices, and unhygienic conditions are some of the common cause for the recent emergence of these multidrug-resistant bacterial strains17. If timely untreated such ESBLs and MBLs can cause major public health problems, such as UTIs and blood poisoning. One of the most common bacterial diseases in women and the elderly individual is urinary tract infection (UTI). This sort of disorder can cause less severe existence threatening illnesses alternatively the affected person experienced big distress18. Furthermore, this infection is linked to significant healthcare and societal costs especially in the United States, where UTIs accountable for 7 M clinic visits per year19. Except in newborns and the elderly, women are more likely than males to contract the illness, with estimates ranging from 40–50 percent of women having one episode and 20–30 percent having multiple episodes20. UTI and recurrent UTI (rUTI) are the most common illnesses in women aged 1 to 50 years20. rUTI is most commonly linked to urinary tract anomalies discovered after kidney transplantation or as a result of end-stage renal illness. Furthermore, a considerable minority of patients with rUTI have no known cause21. UTI is caused primarily by bacteria, although it can also be caused by other microorganisms such as viruses and fungi, which are uncommon etiologic factors22. There are two types of infections: complex and simple. The most frequent type of UTI is uncomplicated UTI, which occurs when there are no functional or anatomical abnormalities in the urinary system. The more complicated one happens when there is an irregular urinary tract, which increases infection susceptibility17. In both community and hospital infections, E. coli is the most common uropathogen (75–90 percent of isolates), however other pathogenic microorganism such as P. mirabilis, S. saprophyticus (with specifically frequent isolation from moniae), and P. aeruginosa are every less common18-20. Fimbrial adhesions are produced by uropathogenic bacteria and adhere to glycolipids and glycoproteins on the epithelial membrane. Bacteria can overpower the flow of urine in this way and remain in the urinary system. Toxins, hemolysin, and colony-necrotizing factors are among the additional chemicals produced by bacteria. These chemicals compromise epithelial integrity, allowing germs to infiltrate and thereby increase the risk of infection23. Uropathogens can also internalize and divide within host epithelial cells, providing a reservoir for recurrent infection18. The widespread usage of antibiotics in recent decades has led in the creation of antibiotic-resistant microorganisms and the spread of antibiotic resistance. A promising method to prevention and treatment is also advantageous because to the persistent nature of UTIs and the possibility for antibiotic resistance. Various methods have been developed in recent years to address the issues related with antibiotic resistance24-26. In this paper, synthesis of Co2+, Mn2+ and Fe3+ complexes with nitrogen-oxygen containing ligands is discussed. The structures of the synthesized complexes have been analyzed by Mass FTIR, 1HNMR and the antimicrobial screening of compounds was performed against different fungal strains and bacterial strains. UTI activity against E. coli, P. aeruginosa, K. pneumoniae bacteria.
MATERIAL AND TECHNIQUES:
Reagents and chemicals:
2-decanone, semicarbazide hydrochloride, sodium acetate, Co, Mn, and Fe chloride and nitrate salts.
Instrumentation:
Microwave oven, IR spectrometer, NMR Spectrometer, Mass Spectrometer XRD and TGA.
Selection of Solvents:
Ether, pet ether, ethanol, methanol, DMSO, distilled water
Preparation of ligand C11H23N3O (SB):
The ligand (E)-2-(decan-2-ylidene) hydrazine-1-carboxamide was synthesized by adding an aqueous solution of semicarbazide hydrochloride (0.01mole) in a hot methanolic solution of 2-decanone (0.01mole) in presence of sodium acetate (0.01mole) with regular stirring on a magnetic stirrer. The resulting mixture was then irradiated under microwave for 6 min at 90○C. After reaction time, it is cooled to room temperature and allowed it to stand overnight for crystallization. A milky white color reaction product is precipitated out which was filtered off, rinsed in distilled water, cold methanol and lastly dried in a desiccator using silica gel as moisture absorbent.
Scheme 1 Schiff base ligand synthesis
Schiff Base (SB) Metal Complexes synthesis:
The weighed amount of Co2+, Mn2+ and Fe3+ salts [CoCl2.6H2O and Co(NO3)2.6H2O] [MnCl2.4H2O] [FeCl3 and Fe(NO3)2.9H2O] (0.002 mol) was added to the methanolic solution of (E)-2-(decan-2-ylidene) hydrazine-1-carboxamide (0.004 mol) i.e., 1:2 stoichiometry proportion. The chloride and nitrate salts of Co2+, Mn2+ and Fe3+ were added in the form of hot methanolic solution. The resulting mixtures were irradiated for 6-7, 7-9 and 5-7 min in microwave oven. After completion of the reaction, the colored solids came into existence, which was filtered, rinsed with 50% ethanolic solution and finally dried in desiccators. The analytical data and physical properties of Co2+, Mn2+ and Fe3+ complexes of (E)-2-(decan-2-ylidene) hydrazine-1-carboxamide are reported.
Scheme 2 Schiff base (SB) metal complexes [M = Co2+, Mn2+and Fe3+] synthesis pathway
Study of antimicrobial action:
The Azomethine ligand and its metal complexes were tested in vitro antimicrobial action towards S. aureus and E. coli and fungi C. albicans and A. fumigatus. The disc diffusion technique27,28 was used to examine the qualitative antibacterial activity of the synthesized compounds. Each test organism was inoculated onto a nutrient agar plate and incubated at 37⁰C for 24 hrs. and for fungi 28oC for C. albicans (24 hr.) and 37oC for A. fumigatus (2-3 days). to get the primary culture. To attain 106-108 CFUs, the suspension turbidity was compared with 0.5 McFarland standard. The bacterial suspension (0.1mL) was inoculated onto Mueller Hinton plate and the sterile discs that have been impregnated with the test compounds were firmly placed on it. The inhibitory zone was measured in millimetres after the test was injected for 24hrs. at 37°C. Dimethylsulphoxide (DMSO) were used as standard antibacterial drug and manage solvent respectively.
RESULT AND DISCUSSION:
The synthesized compounds were characterized by melting point, Infra-Red (IR), NMR, XRD, Mass (ESI-MS) spectroscopy and thermal analysis29.
Elemental Analysis:
Analysis results is noted in table 1.
IR spectroscopy:
The ligand L consists of potential donor sites such as azomethine (−C=N), an amide group (−CONH2), (C−O−C) linkage and amino (−NH) groups which have a tendency to coordinate with metal ions. Different bands were visible in the IR spectra of the ligand L at 3289, 1668, 1564, and 1160 cm–1. The IR bands of the ligand and metal complexes are listed in Table 2. The FTIR spectra of ligand observed in the range of between 1668–1639 cm–1 and 1533-1564 cm–1 assigned to ν(>C=O) and ν(>C=N) groups which are shifted to the lesser frequencies around 1533-1639 cm−1 upon complexation shows ligand attach with metal complex which confirmed that ν(>C=N) containing in the coordination. Bands of strong absorption in the range 1364-629 cm–1, in the metal complexes. It was confirmed that the nitrogen behaves as bidentate ligands. The presence of a low medium intensity band in the region at ~449 to 421 cm−1 metal complexes further confirms nitrogen role in coordination. (Table-2).
Ligand IH-NMR spectra:
1H NMR
spectrum of 2-decanone semicarbazone ligand (400 MHz, DMSO‐d6) with
the use of TMS as a standard. The chemical shift of different types of proton
of ligand. 1H-NMR spectrum exhibits following signals: δ 8.91
ppm which indicated the presence of proton of (s, 1H, HN), δ 6.18 ppm (s,
2H, -NH2,) δ 3.37 ppm is due to existence of proton of methyl
group (s, 6H, ‐CH3).
I3C-NMR spectrum of Ligand:
13 C NMR spectra of ligand (400 MHz, DMSO- d6): δ= 157.86ppm, 149.90ppm, 40.576ppm 39.95ppm, 29.28 ppm, 22.55ppm, 16.01ppm, 14.43 ppm. In the 13C-NMR spectra of the ligand the position of azomethine carbon peak at δ 157.86ppm of the ligand.