Synthesis and biological evaluation of novel fluconazole analogues bearing 1,3,4-oxadiazole moiety as potent antifungal agents

Strategies of targeting CYP51 for IFIs therapy: Emerging prospects, opportunities and challenges

CYP51, a monooxygenase associated with the sterol synthesis pathway, is responsible for the catalysis of the 14-methyl hydroxylation reaction of lanosterol precursors. This enzyme is widely present in microorganisms, plants, and mammals. In mammals, CYP51 plays a role in cholesterol production, oligodendrocyte formation, oocyte maturation, and spermatogenesis. In fungal cells, CYP51 is an enzyme that synthesizes membrane sterols. By inhibiting fungal CYP51, ergosterol synthesis can be inhibited and ergosterol membrane fluidity is altered, resulting in fungal cell apoptosis. Thus, targeting CYP51 is a reliable antifungal strategy with important implications for the treatment of invasive fungal infections (IFIs). Many CYP51 inhibitors have been approved by the FDA for clinical treatment. However, several limitations of CYP51 inhibitors remain to be resolved, including fungal resistance, hepatotoxicity, and drug-drug interactions. New broad-spectrum, anti-resistant, highly selective CYP51 inhibitors are expected to be developed to enhance clinical efficacy and minimize adverse effects. Herein, we summarize the structural features and biological functions of CYP51 and emphatically analyze the structure-activity relationship (SAR) and therapeutic potential of different chemical types of small-molecule CYP51 inhibitors. We also discuss the latest progress of novel strategies, providing insights into new drugs targeting CYP51 for clinical practice.

Efficient selective targeting of Candida CYP51 by oxadiazole derivatives designed from plant cuminaldehyde

Candida infection represents a global threat with associated high resistance and mortality rate. Azoles such as the triazole drug fluconazole are the frontline therapy against invasive fungal infections; however, the emerging multidrug-resistant strains limit their use. Therefore, a series of novel azole UOSO1-15 derivatives were developed based on a modified natural scaffold to combat the evolved resistance mechanism and to provide improved safety and target selectivity. The antifungal screening against C. albicans and C. auris showed that UOSO10 and 12-14 compounds were the most potent derivatives. Among them, UOSO13 exhibited superior potent activity with MIC50 values of 0.5 and 0.8 μg mL-1 against C. albicans and C. auris compared to 25 and 600 μg mL-1 for fluconazole, respectively. UOSO13 displayed significant CaCYP51 enzyme inhibition activity in a concentration-dependent manner with an IC50 10-fold that of fluconazole, while exhibiting no activity against human CYP50 enzyme or toxicity to human cells. Furthermore, UOSO13 caused a significant reduction of Candida ergosterol content by 70.3% compared to a 35.6% reduction by fluconazole. Homology modeling, molecular docking, and molecular dynamics simulations of C. auris CYP51 enzyme indicated the stability and superiority of UOSO13. ADME prediction indicated that UOSO13 fulfils the drug-likeness criteria with good physicochemical properties.

Cholyl 1,3,4-oxadiazole hybrid compounds: design, synthesis and antimicrobial assessment

A new chemical library based on the hybridization of cholic acid with the heterocyclic moiety 1,3,4-oxadizole was synthesized, and tested for antimicrobial activity against Gram-positive, Gram-negative bacteria, and fungi. Among the synthesized compounds, the most potent derivatives against S. aureus were 4t, 4i, 4p, and 4c with MIC values between 31 and 70 µg/mL, while compound 4p was the most active one against Bacillus subtilis with a MIC value of 70 µg/mL. Interestingly, compounds 4a and 4u exerted selective activity against Gram-positive bacteria. The synthesized compounds showed good activity against A. fumigatus and C. albicans and compound 4v exhibited selective activity against fungi only.

Antimicrobial Activity of 1,3,4-Oxadiazole Derivatives

The worldwide development of antimicrobial resistance forces scientists to search for new compounds to which microbes would be sensitive. Many new structures contain the 1,3,4-oxadiazole ring, which have shown various antimicrobial activity, e.g., antibacterial, antitubercular, antifungal, antiprotozoal and antiviral. In many publications, the activity of new compounds exceeds the activity of already known antibiotics and other antimicrobial agents, so their potential as new drugs is very promising. The review of active antimicrobial 1,3,4-oxadiazole derivatives is based on the literature from 2015 to 2021.

Fluconazole analogues with metal-binding motifs impact metal-dependent processes and demonstrate antifungal activity in Candida albicans

Azole antifungals are an important class of antifungal drugs due to their low cost, ability to be administered orally, and broad-spectrum activity. However, their widespread and long-term use have given rise to adaptation mechanisms that render these compounds less effective against common fungal pathogens, including Candida albicans. New antifungals are desperately needed as drug-resistant strains become more prevalent. We recently showed that copper supplementation potentiates the activity of the azole antifungal fluconazole against the opportunistic fungal pathogen C. albicans. Here, we report eight new azole analogues derived from fluconazole in which one triazole group has been replaced with a metal-binding group, a strategy designed to enhance potentiation of azole antifungal activity by copper. The bioactivity of all eight compounds was tested and compared to that of fluconazole. Three of the analogues showed activity against C. albicans and two had lower levels of trailing growth. One compound, Flu-TSCZ, was found to impact the levels, speciation, and bioavailability of cellular metals.

Heterocycle Compounds with Antimicrobial Activity

Background:

Bacterial infections are a growing problem worldwide causing morbidity and mortality mainly in developing countries. Moreover, the increased number of microorganisms, developing multiple resistances to known drugs, due to abuse of antibiotics, is another serious problem. This problem becomes more serious for immunocompromised patients and those who are often disposed to opportunistic fungal infections.

Objective:

The objective of this manuscript is to give an overview of new findings in the field of antimicrobial agents among five-membered heterocyclic compounds. These heterocyclic compounds especially five-membered attracted the interest of the scientific community not only for their occurrence in nature but also due to their wide range of biological activities.

Method:

To reach our goal, a literature survey that covers the last decade was performed.

Results:

As a result, recent data on the biological activity of thiazole, thiazolidinone, benzothiazole and thiadiazole derivatives are mentioned.

Conclusion:

It should be mentioned that despite the progress in the development of new antimicrobial agents, there is still room for new findings. Thus, research still continues.

Metal-free oxidative C(sp3)–H functionalization: a facile route to quinoline formaldehydes from methyl-azaheteroarenes

A facile protocol for the synthesis of quinoline formaldehydes via direct oxidative C–H bonds functionalization of methyl-azaheteroarenes in the presence of I2–DMSO has been described. This method is metal-free and easy to operate. This reaction provided a convenient route for the preparation of a range of important quinoline formaldehydes.

Crystal structure of N 1,N 3-bis(2-hydroxyethyl)-N 1, N 1,N 3,N 3-tetramethylpropane-1,3-diaminium dibromide, C11H28Br2N2O2

C11H28Br2N2O2, triclinic, P1̄ (no. 2), a = 12.0519(11) Å, b = 12.6670(12) Å, c = 12.9161(12) Å, α = 117.088(3)°, β = 92.459(1)°, γ = 108.199(2))°, V = 1627.2(3) Å3, Z = 4, R gt(F) = 0.0645, wR ref(F 2) = 0.1632, T = 298(2) K.

Copper(i)-catalyzed benzylation of triazolopyridine through direct C-H functionalization

A general and efficient copper-catalyzed benzylation reaction of triazolopyridine with N-tosylhydrazones was developed. This reaction forms a C(sp²)-C(sp³) bond through cross-coupling, and represents an exceedingly practical method to afford 3-benzylated triazolopyridines in moderate to good yields. A proposed mechanistic pathway underlying this reaction was outlined. This catalytic transformation should enable broad synthetic applications in functionalization chemistry, allowing the synthesis of new pharmaceutically relevant triazolopyridine derivatives.

A Review Exploring Therapeutic Worth of 1,3,4-Oxadiazole Tailored Compounds

1,3,4-Oxadiazole, a five-membered aromatic ring can be seen in a number of synthetic molecules. The peculiar structural feature of 1,3,4-oxadiazole ring with pyridine type of nitrogen atom is beneficial for 1,3,4-oxadiazole derivatives to have effective binding with different enzymes and receptors in biological systems through numerous weak interactions, thereby eliciting an array of bioactivities. Research in the area of development of 1,3,4-oxadiazole-based derivatives has become an interesting topic for the scientists. A number of 1,3,4-oxadiazole based compounds with high therapeutic potency are being extensively used for the treatment of different ailments, contributing to enormous development value. This work provides a systematic and comprehensive review highlighting current developments of 1,3,4-oxadiazole based compounds in the entire range of medicinal chemistry such as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents. It is believed that this review will be of great help for new thoughts in the pursuit for rational designs for the development of more active and less toxic 1,3,4-oxadiazole based medicinal agents.

Oxidative C(sp3)–H functionalization of methyl-azaheteroarenes: a facile route to 1,2,4-triazolo[4,3-a]pyridines

An oxidative [4 + 1] annulation for triazolo[4,3-a]pyridine–quinoline linked diheterocycle synthesis via functionalization of the sp³ C–H bonds of 2-methyl-azaheteroarenes has been developed.

Synthesis, Biological Activity, and Apoptotic Properties of NO-Donor/Enmein-Type ent-Kauranoid Hybrids

Herein, we reported on a series of synthetic nitric oxide-releasing enmein-type diterpenoid hybrids (9a–i). All the target compounds showed potent antibacterial activity against selected Gram-positive bacteria S. aureus and B. subtilis. The antiproliferative activity against human tumor K562, MGC-803, CaEs-17 and Bel-7402 cells, and human normal liver cells L-02 was tested and the structure activity relationships (SARs) were also concluded. Compounds 9b and 9d showed the best activity against S. aureus and B. subtilis with the same minimal inhibitory concentrations (MICs) of 4 and 2 μg/mL, respectively. The derivative 9f displayed IC₅₀ values of 1.68, 1.11, 3.60 and 0.72 μM against the four cancer cell lines above and 18.80 μM against normal liver cells L-02; meanwhile, 9f also released a high level of NO at the time point of 60 min of 22.24 μmol/L. Furthermore, it was also found that 9f induced apoptosis via the mitochondria-related pathway and arrested cell cycle of Bel-7402 cells at S phase. These findings might be important to explore new chemical entities for the main causes of in-hospital mortality of S. aureus infection, combined with a solid tumor.

Antitumor and Antibacterial Derivatives of Oridonin: A Main Composition of Dong-Ling-Cao

Isodon rubescens has been used as a traditional green tea for more than 1000 years and many medicinal functions of I. rubescens are also very useful, such as its well-known antitumor and antibacterial activities. Oridonin, a bioactive ent-kaurane diterpenoid, is the major ingredient of this medicinal tea. Herein, 22 novel oridonin derivatives were designed and synthesized. The antibacterial activity was evaluated for the first time. Compound 12 was the most promising one with MIC of 2.0 μg/mL against B. subtilis, which was nearly 3-fold stronger than positive control chloromycetin. The antiproliferative property was also assayed and compound 19 showed stronger activity than taxol. The apoptosis-inducing ability, cell cycle arrest effect at S phase and influence of mitochondrial membrane potential by 19 in CaEs-17 cancer cells were first disclosed. Based on the above results, the cell apoptosis induced by compound 19 in CaEs-17 cells was most probably involved in the intrinsic apoptotic pathway.

Quantitative and qualitative analysis of the novel antitumor 1,3,4-oxadiazole derivative (GLB) and its metabolites using HPLC-UV and UPLC-QTOF-MS

Fructose-based 3-acetyl-2,3-dihydro-1,3,4-oxadiazole (GLB) is a novel antitumor agent and belongs to glycosylated spiro-heterocyclic oxadiazole scaffold derivative. This research first reported a simple, specific, sensitive and stable high performance liquid chromatography-ultraviolet detector (HPLC-UV) method for the quantitative determination of GLB in plasma. In this method, the chromatographic separation was achieved with a reversed phase C18 column. The calibration curve for GLB was linear at 300 nm. The lower limit of quantification was 10 ng/mL. The precision, accuracy and stability of the method were validated adequately. This method was successfully applied to the pharmacokinetic study in rats for detection of GLB after oral administration. Moreover, the structures of parent compound GLB and its two major metabolites M1 and M2 were identified in plasma using an ultra performance liquid chromatography-electrospray ionization-quadrupole-time of flight- mass spectrometry (UPLC-ESI-QTOF-MS) method. Our results indicated that the di-hydroxylation (M1) and hydroxylation (M2) of GLB are the major metabolites. In conclusion, the present study provided valuable information on an analytical method for the determination of GLB and its metabolites in rats, can be used to support further developing of this antitumor agent.