Synthesis and antimicrobial properties of steroid-based imidazolium salts

Design, synthesis and molecular docking of novel D-ring substituted steroidal 4,5-dihydropyrazole thiazole derivatives that act as iNOS/COX-2 inhibitors with potent anti-inflammatory activity against LPS-induced RAW264.7 macrophage cells

Inflammation, an important biological protective response to tissue damage or microbial invasion, is considered to be an alarming signal for the progress of varied biological complications. Based on the previous reports in the literature that proved the noticeable efficacy of pyrazole and thiazole scaffold as well as nitrogen heterocyclic based compounds against acute and chronic inflammatory disease, a new set of novel D-ring substituted steroidal 4,5-dihydropyrazole thiazole derivatives were synthesized and evaluated their anti-inflammatory activities in vitro. Preliminary structure-activity relationship (SAR) analysis was conducted by their inhibitory activities against nitric oxide (NO) release in lipopolysaccharide (LPS)-induced RAW 264.7 cells, and the optimal compound 12b [3β-hydroxy-pregn-5-en-17β-yl-5'- (o- chlorophenyl)- 1'-(4''- phenyl -[1'', 3'']- thiazol-2''- yl) - 4',5'-dihydro - 1'H-pyrazol - 3'- yl] exhibited more potent anti-inflammatory activity than the positive control treatment methylprednisolone (MPS), with an IC50 value of 2.59 μM on NO production and low cytotoxicity against RAW 264.7 cells. In further mechanism study, our results showed that compound 12b significantly suppressed the production of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and inhibited the expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) through blocking NF-κB p65 nuclear translocation and phosphorylation of IκBα. Compound 12b also attenuated LPS-induced activation of c-Jun amino-terminal kinase (JNK) and p38 phosphorylation in RAW 264.7 cells. Molecular docking study revealed the strong binding affinity of compound 12b to the active site of the COX-2 proteins, which confirmed that compound 12b acted as an anti-inflammatory mediator. These results indicate that steroidal derivatives bearing 4,5-dihydropyrazole thiazole structure might be considered for further research and scaffold optimization in designing anti-inflammatory drugs and compound 12b might be a promising therapeutic anti-inflammatory drug candidate.

Antibacterial activity of withanolides and their structure-activity relationship

Two new withanolides, (17R,20S,22R)-4β-acetoxy-5β,6β-epoxy-19,27-dihydroxy-1-oxo-witha-2,24-dienolide (withalongolide A 4-acetate (5) and (17R,20S,22R)-5β,6β-epoxy-27-hydroxy-1,4-dioxo-witha-24-enolide (9), and seven known withanolides with normal structure (1-4, 6-8) were isolated from aerial parts of Cuatresia colombiana. Several semisynthetic derivatives were prepared from the natural metabolites withaferin A and jaborosalactone 38. The compounds were fully characterized by a combination of spectroscopic methods (1D and 2D NMR and MS). The compounds isolated from C. colombiana, sixteen withanolides previously isolated from different Solanaceae species with different skeletons and semisynthetic derivatives were evaluated for their antibacterial activity against a selected panel of Gram-positive and Gram-negative bacteria. According to the bioactivity against S. aureus and E. faecalis, the compounds evaluated were divided into three groups: compounds with high activity (MIC 0.063 mM), compounds with moderate activity (0.5 mM > MIC > 0.125 mM) and non-active compounds (MIC ≥1 mM); in addition, some structure-activity relationship keys could be inferred.

Recent developments in membrane targeting antifungal agents to mitigate antifungal resistance

Fungal infections cause severe and life-threatening complications especially in immunocompromised individuals. Antifungals targeting cellular machinery and cell membranes including azoles are used in clinical practice to manage topical to systemic fungal infections. However, continuous exposure to clinically used antifungal agents in managing the fungal infections results in the development of multi-drug resistance via adapting different kinds of intrinsic and extrinsic mechanisms. The unique chemical composition of fungal membranes presents attractive targets for antifungal drug discovery as it is difficult for fungal cells to modify the membrane targets for emergence of drug resistance. Here, we discussed available antifungal drugs with their detailed mechanism of action and described different antifungal resistance mechanisms. We further emphasized structure-activity relationship studies of membrane-targeting antifungal agents, and classified membrane-targeting antifungal agents on the basis of their core scaffold with detailed pharmacological properties. This review aims to pique the interest of potential researchers who could explore this interesting and intricate fungal realm.

Antimicrobial Activity of Some Steroidal Hydrazones

Twelve steroid based hydrazones were in silico evaluated using computer program PASS as antimicrobial agents. The experimental evaluation revealed that all compounds have low to moderate antibacterial activity against all bacteria tested, except for B. cereus with MIC at a range of 0.37-3.00 mg/mL and MBC at 0.75-6.00 mg/mL. The most potent appeared to be compound 11 with MIC/MBC of 0.75/1.5 mg/mL, respectively. The evaluation of antibacterial activity against three resistant strains MRSA, E. coli and P. aeruginosa demonstrated superior activity of compounds against MRSA compared with ampicillin, which did not show bacteriostatic or bactericidal activities. All compounds exhibited good antifungal activity with MIC of 0.37-1.50 mg/mL and MFC of 1.50-3.00 mg/mL, but with different sensitivity against fungi tested. According to docking studies, 14-alpha demethylase inhibition may be responsible for antifungal activity. Two compounds were evaluated for their antibiofilm activity. Finally, drug-likeness and docking prediction were performed.

Concise synthesis of E/F ring spiroethers from tigogenin. Carbaanalogs of steroidal sapogenins and their biological activity

A four-step synthesis of five- and six-membered E/F ring spiroethers from tigogenin has been developed. An efficient strategy that features bis-Grignard reaction of dinorcholanic lactone with appropriate bis(bromomagnesio)alkanes followed by acid-mediated spirocyclization was employed to construct a new class of steroid compounds having E and F ring junction as an oxa-carbacyclic system. The synthesized carbaanalogs interact with liposomes and albumin, and also exhibit antibacterial and antifungal activity, demonstrating their pharmacological potential.

Phthalimide-tethered imidazolium salts: Synthesis, characterization, enzyme inhibitory properties, and in silico studies

A series of new imidazolium salts were prepared in good yield by the reaction between 1-alkylimidazole and a variety of alkyl halides. The structures of the compounds were identified by FT-IR, ¹ H NMR, and ¹³ C NMR spectroscopy, elemental analysis, and mass spectrometry. The crystal structure of 1b was determined by the single-crystal X-ray diffraction method. The phthalimide-tethered imidazolium salts exhibited inhibition abilities toward acetylcholinesterase (AChE) and human carbonic anhydrases (hCAs) I and II, with K_i values in the range of 24.63 ± 3.45 to 305.51 ± 35.98 nM for AChE, 33.56 ± 3.71 to 218.01 ± 25.21 nM for hCA I and 17.75 ± 0.96 to 308.67 ± 13.73 nM for hCA II. The results showed that the new imidazolium salts can play a key role in the treatment of Alzheimer's disease, epilepsy, glaucoma, and leukemia, which is related to their inhibition abilities of hCA I, hCA II, and AChE. Molecular docking and in silico absorption, distribution, metabolism, excretion and toxicity studies were used to look into how the imidazolium salts interacted with the specific protein targets. To better visualize and understand the binding positions and the influence of the imidazolium salts on hCA I, hCA II, and AChE conformations, each one was subjected to molecular docking simulations.

Cationic, Steroid-Based Imidazolium Amphiphiles Show Tunable Backbone-Dependent Membrane Selectivity in Fungi

Cationic amphiphiles have been reported to show broad antimicrobial activity. The potential for antimicrobial resistance to these molecules is low owing to their general cell membrane permeabilizing mode of action. However, their applications are often limited by toxicity resulting from their low selectivity for microbial cell membranes. Herein, we report a library of cationic, steroid-based imidazolium amphiphiles that show tunable antifungal activity in a variety of fungal pathogens of the genus Candida. We show that adoption of an ergosterol-derived backbone increases antifungal activity while modestly affecting hemolytic activity, thereby increasing overall selectivity by more than 8-fold in comparison to cholesterol-derived imidazolium salts. We hypothesize that this effect is caused by a privileged integration of the ergosterol-derived salts into fungal membranes leading to increased membrane disorder. We propose that these findings offer a useful platform for the development of improved amphiphilic fungicides.

Efficacy of Prednisolone/Zn Metal Complex and Artemisinin Either Alone or in Combination on Lung Functions after Excessive Exposure to Electronic Cigarettes Aerosol with Assessment of Antibacterial Activity

The use of transition metal complexes as therapeutic compounds has become more and more pronounced. These complexes offer a great diversity of uses in their medicinal applications. Electronic cigarettes (ECs) are an electronic nicotine delivery system that contain aerosol (ECR). The ligation behavior of prednisolone, which is a synthetic steroid that is used to treat allergic diseases and asthma arthritis, and its Zn (II) metal complex were studied and characterized based on elemental analysis, molar conductance, Fourier-transform infrared (FT-IR) spectra, electronic spectra, XRD, scanning electron microscopy (SEM), energy dispersive x-ray (EDX), and transmission electron microscopy (TEM). The FT-IR spectral data revealed that PRD acts as a mono-dentate ligand via oxygen atoms of the carbonyl group. Electronic and FT-IR data revealed that the PRD/Zn (II) metal complexes have square planner geometry. Artemisinin (ART) is the active main constituent of Artemisia annua extract, and it has been demonstrated to exert an excellent antimalarial effect. The experiment was performed on 40 male mice that were divided into the following 7 groups: Control, EC group, PRD/Zn, ART, EC plus PRD/Zn, EC plus ART, and PRD plus combination of PRD/Zn and ART. Serum CRP, IL-6, and antioxidants biomarkers were determined. Pulmonary tissue histology was evaluated. When in combination with Zn administration, PRD showed potent protective effects against pulmonary biochemical alterations induced by ECR and suppressed severe oxidative stress and pulmonary structure alterations. Additionally, PRD/Zn combined with ART prevented any stress on the pulmonary tissues via antioxidant regulation, reducing inflammatory markers CRP and Il-6 and improving antioxidant enzymatic levels more than either PRD or ART alone. Therefore, PRD/Zn combined with ART produced a synergistic effect against any sort of oxidative stress and also improved the histological structure of the lung tissues. These findings are of great importance for saving pulmonary function, especially during pandemic diseases, such as during the COVID-19 pandemic.

Establishment of In Vitro and In Vivo Anticolorectal Cancer Efficacy of Lithocholic Acid-Based Imidazolium Salts

Imidazolium salts (IMSs) are the subject of many studies showing their anticancer activities. In this research, a series of novel imidazolium salts substituted with lithocholic acid (LCA) and alkyl chains of various lengths (S1–S10) were evaluated against colon cancer cells. A significant reduction in the viability and metabolic activity was obtained in vitro for DLD-1 and HT-29 cell lines when treated with tested salts. The results showed that the activities of tested agents are directly related to the alkyl chain length, where S6–S8 compounds were the most cytotoxic against the DLD-1 line and S4–S10 against HT-29. The research performed on the xenograft model of mice demonstrated a lower tendency of tumor growth in the group receiving compound S6, compared with the group receiving 5-fluorouracil (5-FU). Obtained results indicate the activity of S6 in the induction of apoptosis and necrosis in induced colorectal cancer. LCA-based imidazolium salts may be candidates for chemotherapeutic agents against colorectal cancer.

Steroid-Functionalized Imidazolium Salts with an Extended Spectrum of Antifungal and Antibacterial Activity

It is established that high rates of morbidity and mortality caused by fungal infections are related to the current limited number of antifungal drugs and the toxicity of these agents. Imidazolium salts as azole derivatives can be successfully used in the treatment of fungal infections in humans. Steroid-functionalized imidazolium salts were synthesized using a new, more efficient method. As a result, 20 salts were obtained with high yields, 12 of which were synthesized and characterized for the first time. They were derivatives of lithocholic acid and 3-oxo-23,24-dinorchol-4-ene-22-al and were fully characterized by ¹H and ¹³C nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and high resolution mass spectrometry (HRMS). Due to the excellent activity against bacteria and Candida albicans, new research was extended to include tests on five species of pathogenic fungi and molds: Aspergillus niger ATCC 16888, Aspergillus fumigatus ATCC 204305, Trichophyton mentagrophytes ATCC 9533, Cryptococcus neoformans ATCC 14116, and Microsporum canis ATCC 11621. The results showed that the new salts are almost universal antifungal agents and have a broad spectrum of activity against other human pathogens. To initially assess the safety of the synthesized salts, hemocompatibility with host cells and cytotoxicity were also examined. No toxicity was observed at the concentration at which the compounds were active against pathogens.

Applications of medicinal chemistry for drug discovery against Acanthamoeba infections

Acanthamoeba is a genus of free-living amoebae, pervasively found in the environment. Most of its pathogenic species are the causative agent of sight-threatening Acanthamoeba keratitis and fatal granulomatous amoebic encephalitis. Despite the advancements in the field of chemotherapy, treating Acanthamoeba infections is still challenging due to incomplete knowledge of the complicated pathophysiology. In case of infection, the treatment regimen for the patients is often ineffective due to delayed diagnosis, poor specificity, and side-effects. Besides the resistance of Acanthamoeba cysts to most of the drugs, the recurrence of infection further complicates the recovery. Thus, it is necessary to develop an effective treatment which can eradicate these rare, but serious infections. Based on various computational and in vitro studies, it has been established that the synthetic scaffolds such as heterocyclic compounds may act as potential drug leads for the development of antiamoebic drugs. In this review, we report different classes of synthetic compounds especially heterocyclic compounds which have shown promising results against Acanthamoeba. Moreover, the antiamoebic activities of synthetic compounds with their possible mode of actions against Acanthamoeba, have been summarized and discussed in this review.

Diosgenin Derivatives as Potential Antitumor Agents: Synthesis, Cytotoxicity, and Mechanism of Action

Thirty-two new diosgenin derivatives were designed, synthesized, and evaluated for their cytotoxic activities in three human cancer cell lines (A549, MCF-7, and HepG2) and normal human liver cells (L02) using an MTT assay in vitro. Most compounds, especially 8, 18, 26, and 30, were more potent when compared with diosgenin. The structure-activity relationship results suggested that the presence of a succinic acid or glutaric acid linker, a piperazinyl amide terminus, and lipophilic cations are all beneficial for promoting cytotoxic activity. Notably, compound 8 displayed excellent cytotoxic activity against HepG2 cells (IC₅₀ = 1.9 μM) and showed relatively low toxicity against L02 cells (IC₅₀ = 18.6 μM), showing some selectivity between normal and tumor cells. Studies on its cellular mechanism of action showed that compound 8 induces G0/G1 cell cycle arrest and apoptosis in HepG2 cells. Predictive studies indicated that p38α mitogen-activated protein kinase (MAPK) is the optimum target of 8 based on its 3D molecular similarity, and docking studies showed that compound 8 fits well into the active site of p38α-MAPK and forms relatively strong interactions with the surrounding amino acid residues. Accordingly, compound 8 may be used as a promising lead compound for the development of new antitumor agents.

Recent Progress in Bile Acid-Based Antimicrobials

With the emergence of drug-resistant bacteria and the formation of biofilms by bacteria and fungi, microbial infections gradually threaten global health. Natural antimicrobial peptides (AMPs) have low susceptibility for developing resistance due to the membrane targeted mechanism, but instability and high manufacturing cost limit their applications in clinic. Bile acids, a group of steroids in the human body, with high stability, biocompatibility, and inherent facial amphiphilic structure similar to the characteristics of AMPs, have been applied to the biological field, such as drug delivery systems, self-healing hydrogels, antimicrobials, and so on. In this review, we mainly focus on the different classes of bile acid-based antimicrobials in recent years. Various designs and methods for the preparation of unimolecular antimicrobials with bile acid skeletons are first introduced, including coupling of primary amine, quaternary ammonium, and amino acid units with bile acid skeletons. Some representative oligomeric antimicrobials, including dimers of bile acids, are summarized. Finally, macromolecular antimicrobials bearing some positive charges at the main chain or side chain and interaction mechanisms of these bile acid-based antimicrobials are discussed.

Dehydroepiandrosterone derived imidazolium salts and their antimicrobial efficacy

Hybrid molecules consisting of steroid-imidazolium salts reveal interesting biological properties, especially regarding antimicrobial activities. Novel dehydroepiandrosterone derived imidazolium salts (11 salts) with side chains of different lengths were obtained in an efficient and straightforward synthetic route. Antimicrobial properties of new salts were examined by determining their minimum inhibitory concentrations (MICs). They were studied against several strains of bacteria, including clinical isolates of MRSA, and fungi. New compounds showed high activity against Gram-positive bacteria and Candida albicans as well as good compatibility with the representatives of the host cells when applied at concentrations corresponding to MIC value. The studies indicated high antimicrobial efficacy of imidazolium salts against the above-mentioned microorganisms with low hemolytic activity at a concentration that restricts the growth of the microorganisms. The interference of salts with the immune defense system, the influence on the biological activity of monocytes/macrophages measured by their viability and metabolic activity was also studied. The new compounds have shown immunoprotective properties.

Silver (I) N-Heterocyclic Carbenes Carbosilane Dendritic Systems and Their Imidazolium-Terminated Analogues as Antibacterial Agents: Study of Their Mode of Action

Spherical dendrimers and dendrons containing silver(I) N-heterocyclic carbenes (Ag(I)-NHC) and additionally bow-tie metal-free dendritic systems were synthesized in a simple and straightforward synthetic procedure and subsequently characterized. The antibacterial activity was evaluated, and in parallel, a comparative study with the cationic analogue precursors was performed to explore the effect of silver ions in the dendritic structure. Other parameters, such as topology, generation, and hydrophobicity, of the imidazole substituents were also studied. All these dendritic systems presented antibacterial activity against three different bacterial strains, two Gram-positive (Staphylococcus aureus and Bacillus subtilis) and one Gram-negative (Escherichia coli). Several assays were conducted to elucidate their mechanism of action against Bacillus subtilis, by using bacterial biosensors or specific probes and fluorescent proteins sensitive to changes in the cell membrane potential. These studies are specially focused on the role of the polyvalence of our systems containing silver atoms, which may provoke interesting effects in the mode of action.

Environmentally responsive and anti-bugs textile finishes - Recent trends, challenges, and future perspectives

Bugs, such as microorganisms and insects, are present in the environment and sometimes can be health-hazardous if the living environment is not maintained following proper hygienic regulations. In the present scenario of increasing public awareness, environmental consciousness, and growing demand for easy-care, and disinfected textiles, the manufacturing of protective and easy-to-care textiles has become a key necessity of the modern world. Comfortable, clean, hygienic, antimicrobial, and insect repelling properties of textile goods are gaining the accelerating research momentum as a basic requirement to produce multifunctional textiles. These functional finishes have numerous applications such as in-home textiles, bed nets, and tenting, camping gear as well as in military uniforms. Synthetic antimicrobial and insect repellents are quite effective against insects and microscopic organisms but are slightly toxic to the human being and the environment. To overcome these problems, researchers are considering natural agents for functional finishes, but their effectiveness is less durable to textile material. Besides needful advantages, the excessive use of dyes in finishing processes heavily required washing cycles and ultimately release various types of hazardous dyes or wasteful effluents in the environment. This review reports the chemical composition and recent developments in textile finishes, particularly antimicrobial and insect repellent textile finishes. A large number of commonly used antimicrobial agents (i.e. chitosan, zwitterionic compounds, silver and silver-based compounds, titanium dioxide nanoparticles, imidazolium salts, triclosan and quaternary ammonium salts) and insect repellent textile finishes (i.e. N‑N‑diethyl‑m‑toluamide, permethrin, cypermethrin, pyrethrum, picaridin, bioallethrin, citriodiol and essential oils) have been presented. Finally, the review is wrapped up with major research gaps/challenges, concluding remarks, and future opportunities in this area of research.