Synthesis of amino acid appended indoles: Appreciable anti-fungal activity and inhibition of ergosterol biosynthesis as their probable mode of action

Recent report on indoles as a privileged anti-viral scaffold in drug discovery

In recent years, viral infections such as COVID-19, Zika virus, Nipah virus, Ebola, Influenza, Monkeypox, and Dengue have substantially impacted global health. These outbreaks have led to heightened global health initiatives and collaborative efforts to address and mitigate these significant threats effectively. Thus, developing antiviral treatments and research in this field has become highly important. Heterocycles, particularly indole motifs, have been a valuable resource in drug discovery, as they can be used as treatments or inspire the synthesis of new potent candidates. Indole-containing drugs, such as enfuvirtide (T-20), arbidol, and delavirdine, have demonstrated significant efficacy in treating viral diseases. This review aims to comprehensively assess the latest research and developments in novel indoles as potential scaffolds for antiviral activity. We have compiled detailed information about indoles as potential antivirals by conducting a thorough literature survey from the past ten years. The review includes discussions on synthetic protocols, inhibitory concentrations, SAR study, and computational study. This review shall identify new antiviral indoles that may help to combat new viral threats in the future.

Phytochemical profiling, spectroscopic identification of active compounds, and mechanism of the anticandidal properties of Datura stramonium L. using SwissADMET prediction and molecular docking analysis

BACKGROUND

Datura stramonium L., a wild-growing herb, has been traditionally used to treat various ailments, including toothache, asthma, rheumatism, epilepsy, and alopecia. Scientific evidence supports its anticancer, anti-inflammatory, anti-asthmatic, anticholinergic, antifungal, and antibacterial properties.

AIM

This study aimed to isolate, characterize, and identify the most potent anticandidal compounds inhibiting the growth of Candida spp., while also predicting their drug-likeness and toxicity profiles.

METHOD

The anticandidal activity of D. stramonium leaf extracts was assessed using the Agar well-diffusion method and minimum inhibitory concentration (MIC) was determined by the broth dilution method. The most active extract was selected for column chromatography. Different fractions were collected and screened against pathogenic Candida spp. The most active fraction was subjected to Gas chromatography-Mass spectrometry (GC-MS), Fourier Transform-Infrared Spectroscopy (FT-IR), and Nuclear Magnetic Resonance (NMR) analysis. Additionally, computational tools such as molecular docking and ADMET prediction provided further insights into the molecular interactions between the target enzymes.

RESULTS

In vitro anticandidal activity demonstrated that the ethyl acetate extract exhibited significant activity against human pathogenic Candida spp., with the highest zones of inhibition against Candida guilliermondii (20.33 ± 0.56 mm), Candida tropicalis (16.33 ± 0.58 mm), and Candida albicans (14.66 ± 1.05 mm), with a minimum inhibitory concentration (MIC) value of 25 μg/ml. Additionally, the most potent fraction (F8) obtained from the Column revealed significant anticandidal activity. GC-MS analysis of the F8 fraction indicated the presence of 23 compounds, with the major compounds being Phthalic acid, di (2-propylpentyl) ester (Compound 1), Pentadecane (Compound 2), Octadecane (Compound 3), Benzoic acid, 3-Amino-5-Hydroxy-, Methyl ester (Compound 4), and 1,2-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester (Compound 5). This study reports all 23 compounds from D. stramonium for the first time. Furthermore, NMR studies confirmed the presence of Phthalic acid, di (2-propylpentyl) ester as the most abundant compound, designated as compound 1. Finally, docking analysis revealed that compound 1 showed good binding affinities for the tested enzymes, with the highest binding scores of -7.084 kcal/mol and -7.030 kcal/mol with Lanosterol 14-alpha demethylase (PDB ID: 5JLC, 5TZ1). The results of the in silico pharmacokinetic and drug-likeness properties indicated that compound 1 is a potential anticandidal drug candidate.

CONCLUSION

This study highlights that 23 compounds were reported from the leaf extract of D. stramonium for the first time. The findings suggest that compound 1 can be considered a new anticandidal drug candidate.

Recent advances in antifungal drug development targeting lanosterol 14α-demethylase (CYP51): A comprehensive review with structural and molecular insights

Fungal infections are posing serious threat to healthcare system due to emerging resistance among available antifungal agents. Among available antifungal agents in clinical practice, azoles (diazole, 1,2,4-triazole and tetrazole) remained most effective and widely prescribed antifungal agents. Now their associated side effects and emerging resistance pattern raised a need of new and potent antifungal agents. Lanosterol 14α-demethylase (CYP51) is responsible for the oxidative removal of 14α-methyl group of sterol precursors lanosterol and 24(28)-methylene-24,25-dihydrolanosterol in ergosterol biosynthesis hence an essential component of fungal life cycle and prominent target for antifungal drug development. This review will shed light on various azole- as well as non-azoles-based derivatives as potential antifungal agents that target fungal CYP51. Review will provide deep insight about structure activity relationship, pharmacological outcomes, and interactions of derivatives with CYP51 at molecular level. It will help medicinal chemists working on antifungal development in designing more rational, potent, and safer antifungal agents by targeting fungal CYP51 for tackling emerging antifungal drug resistance.

A novel series of dipeptide derivatives containing indole-3-carboxylic acid conjugates as potential antimicrobial agents: the design, solid phase peptide synthesis, in vitro biological evaluation, and molecular docking study

A new library of peptide-heterocycle hybrids consisting of an indole-3-carboxylic acid constituent conjugated with short dipeptide motifs was designed and synthesized by using the solid phase peptide synthesis methodology. All the synthesized compounds were characterized by spectroscopic techniques. Additionally, the synthesized compounds were subjected to in vitro antimicrobial activities. Two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive (Streptococcus pyogenes and Staphylococcus aureus) were used for the evaluation of the antibacterial activity of the targeted dipeptide derivatives. Good antibacterial activity was observed for the screened analogues by comparing their activities with that of ciprofloxacin, the standard drug. Also, two fungi (Aspergillus niger and Candida albicans) were employed for the evaluation of the antifungal activity of the synthesized compounds. When compared to the standard drug Fluconazole, it was observed that the screened analogues exhibited good antifungal activity. In continuation, all the synthesized derivatives were subjected to integrated molecular docking studies and molecular dynamics simulations to investigate binding affinities, intermolecular interaction networks, and conformational flexibilities with deoxyribonucleic acid (DNA) gyrase and lanosterol-14-alpha demethylase. The molecular docking studies revealed that indole-3-carboxylic acid conjugates exhibited encouraging binding interaction networks and binding affinity with DNA gyrase and lanosterol-14 alpha demethylase to show antibacterial and antifungal activity, respectively. Such synthesis, biological activity, molecular dynamics simulations, and molecular docking studies of short peptides with an indole conjugate unlock the door for the near future advancement of novel medicines containing peptide-heterocycle hybrids with the ability to be effective as antimicrobial agents.

Bacillus Metabolites: Compounds, Identification and Anti-Candida albicans Mechanisms

Candida albicans seriously threatens human health, especially for immunosuppressed groups. The antifungal agents mainly include azoles, polyenes and echinocandins. However, the few types of existing antifungal drugs and their resistance make it necessary to develop new antifungal drugs. Bacillus and its metabolites has antifungal activity against pathogenic fungi. This review introduces the application of Bacillus metabolites in the control of C. albicans in recent years. Firstly, several compounds produced by Bacillus spp. are listed. Then the isolation and identification techniques of Bacillus metabolites in recent years are described, including high-precision separation technology and omics technology for the separation of similar components of Bacillus metabolites. The mechanisms of Bacillus metabolites against C. albicans are distinguished from the inhibition of pathogenic fungi and inhibition of the fungal virulence factors. The purpose of this review is to systematically summarize the recent studies on the inhibition of pathogenic fungi by Bacillus metabolites. The review is expected to become the reference for the control of pathogenic fungi such as C. albicans and the application of Bacillus metabolites in the future.

Evaluation of the Anti-Histoplasma capsulatum Activity of Indole and Nitrofuran Derivatives and Their Pharmacological Safety in Three-Dimensional Cell Cultures

Histoplasma capsulatum is a fungus that causes histoplasmosis. The increased evolution of microbial resistance and the adverse effects of current antifungals help new drugs to emerge. In this work, fifty-four nitrofurans and indoles were tested against the H. capsulatum EH-315 strain. Compounds with a minimum inhibitory concentration (MIC₉₀) equal to or lower than 7.81 µg/mL were selected to evaluate their MIC₉₀ on ATCC G217-B strain and their minimum fungicide concentration (MFC) on both strains. The quantification of membrane ergosterol, cell wall integrity, the production of reactive oxygen species, and the induction of death by necrosis–apoptosis was performed to investigate the mechanism of action of compounds 7, 11, and 32. These compounds could reduce the extracted sterol and induce necrotic cell death, similarly to itraconazole. Moreover, 7 and 11 damaged the cell wall, causing flaws in the contour (11), or changing the size and shape of the fungal cell wall (7). Furthermore, 7 and 32 induced reactive oxygen species (ROS) formation higher than 11 and control. Finally, the cytotoxicity was measured in two models of cell culture, i.e., monolayers (cells are flat) and a three-dimensional (3D) model, where they present a spheroidal conformation. Cytotoxicity assays in the 3D model showed a lower toxicity in the compounds than those performed on cell monolayers. Overall, these results suggest that derivatives of nitrofurans and indoles are promising compounds for the treatment of histoplasmosis.

Two C(sp3)-F Bond Activation in a CF3 Group: ipso-Defluorinative Amination Triggered 1,3-Diamination of (Trifluoromethyl)alkenes with Indoles, Carbazoles, Pyrroles, and Sulfonamides

A novel strategy enabled cleavage of two C(sp³)-F bonds in a CF₃ group is reported. Triggered by ipso-defluorinative amination, this 1,3-diamination of (trifluoromethyl)alkenes with indoles, carbazoles, pyrroles, and sulfonamides gave acyclic 1,3-diamine products bearing a monofluoroalkene moiety in high yields with good to excellent Z/E selectivities. Preliminary mechanistic studies enable the isolation of the reaction intermediate and indicate that a unique sequential ipso-/γ-selective defluorinative amination pathway is involved in this transformation.

Novel naphthylamide derivatives as dual-target antifungal inhibitors: Design, synthesis and biological evaluation

Fungal infections have become a serious medical problem due to the high infection rate and the frequent emergence of drug resistance. Squalene epoxidase (SE) and 14α-demethylase (CYP51) are considered as the important antifungal targets, they can show the synergistic effect on antifungal therapy. In the study, a series of active fragments were screened through the method of De Novo Link, and these active fragments with the higher Ludi_Scores were selected, which can show the obvious binding ability with the dual targets (SE, CYP51). Subsequently, three series of target compounds with naphthyl amide scaffolds were constructed by connecting these core fragments, and their structures were synthesized. Most of compounds showed the antifungal activity in the treatment of pathogenic fungi. It was worth noting that compounds 10b-5 and 17a-2 with the excellent broad-spectrum antifungal properties also exhibited the obvious antifungal effects against drug-resistant fungi. Preliminary mechanism study has proved these target compounds can block the biosynthesis of ergosterol by inhibiting the activity of dual targets (SE, CYP51). Furthermore, target compounds 10-5 and 17a-2 with low toxicity side effects also demonstrated the excellent pharmacological effects in vivo. The molecular docking and ADMET prediction were performed, which can guide the optimization of subsequent lead compounds.

Data on molecular docking of tautomers and enantiomers of ATTAF-1 and ATTAF-2 selectivty to the human/fungal lanosterol-14α-demethylase

The data have been obtained for tautomers and enantiomers of ATTAF-1 and ATTAF-2 that were developed based on antifungal standard drugs with triazole scaffold. These compounds were docked into the human and fungal lanosterol-14α-demethylase. In order to validate the data, 8 standard triazole antifungal drugs (Fluconazole, Itraconazole, Posaconazole, Ravuconazole, Albaconazole, Voriconazole, Isavuconazole and Efinaconazole) were also docked into the human and fungal lanosterol-14α-demethylase. The binding conformations of these molecules and their interactions with lanosterol-14α-demethylase may inform the development of further small molecule lanosterol-14α-demethylase inhibitors with significant selectivity toward this enzyme. The analysis has done on the basis of type of interactions (bond type and distance). The length of the Fe-N coordination bond for (R)-N2-ATTAF-1 and (S)-N1-ATTAF-2 complexes is obtained 6.36 and 4.19 Å, respectively and about 2 Å in the other tautomer and enantiomer complexes, reflecting the lower basicity of the N-4 atom in the 1,2,4-triazole ring of (R)-N2-ATTAF-1 and (S)-N1-ATTAF-2 in comparison with the N-4 atom in the 1,2,4-triazole ring in other tautomers and enantiomers and supporting higher selectivity of (R)-N2-ATTAF-1 and (S)-N1-ATTAF-2 towards the target CYP51 enzymes vs. human. Interestingly, we have investigated unfavorable interactions (donor-donor) with TRP239 and MET378 for (R)-N2-ATTAF-1 and (S)-N1-ATTAF-2, respectively. These unfavorable interactions also have been seen in case of posaconazole and isavuconazole. The data presented in this article are related to the research paper entitled "In silico prediction of ATTAF-1 and ATTAF-2 selectivity towards human/fungal lanosterol 14α-demethylase using molecular dynamic simulation and docking approaches".

Silver nanoparticles as antimicrobial therapeutics: current perspectives and future challenges

Utility of silver metal in antimicrobial therapy is an accepted practice since ages that faded with time because of the identification of a few silver resistant strains in the contemporary era. A successive development of antibiotics soon followed. However, due to an indiscriminate and unregulated use coupled with poor legal control measures and a dearth of expertise in handling the critical episodes, the antibiotics era has already seen a steep decline in the past decades due to the evolution of multi-drug resistant 'superbugs' which pose a sizeable challenge to manage with. Due to limited options in the pipeline and no clear strategy in the forefront, the aspirations for novel, MDR focused drug discovery to target the 'superbugs' arose which once again led to the rise of AgNPs in antimicrobial research. In this review, we have focused on the green routes for the synthesis of AgNPs, the mode of microbial inhibition by AgNPs, synergistic effect of AgNPs with antibiotics and future challenges for the development of nano-silver-based therapeutics.

Structure-based virtual screening and ADME/T-based prediction analysis for the discovery of novel antifungal CYP51 inhibitors

With the increasing incidence of pathogenic fungi and drug-resistant fungi in clinic, it has become very important to develop the novel rate-limiting enzyme 14α-demethylase (CYP51) as an antifungal inhibitor. In this study, a method involving structure-based virtual screening was employed. First, a publicly available database was obtained from the Dow Chemical Company, and the database was screened by the designed pharmacophore model of CYP51 inhibitors. Then, the pharmacophore search hits were docked into the CYP51 crystal structure. Finally, sixteen compounds were selected for in vitro antifungal inhibition assay, and most of the compounds showed a certain degree of antifungal activity. In particular, compounds 3, 4, and 9 exhibited significant antifungal and anti-drug resistance activities by blocking the synthesis of ergosterol. The molecular docking and ADME/T properties of the compounds 3, 4, and 9 were further predicted, and the results indicated that they can form hydrophobic and coordination interactions with the active sites of CYP51. At the same time, compounds 4 and 9 showed promising drug-like properties. This study reveals that the compounds can be further optimized and developed as lead compounds.

Identification of an indole–triazole–amino acid conjugate as a highly effective antifungal agent

Compounds constructed by the grafting of amino acid and triazole with an indole moiety were synthesized and investigated for antifungal activities wherein one of the compounds gave highly promising results.