Research Article
Indole-derived chalcones as anti-dermatophyte agents: In vitro evaluation and in silico study

https://doi.org/10.1016/j.compbiolchem.2019.107189Get rights and content

Highlights

  • Indole-derived methoxylated chalcones were introduced as anti-dermatophyte agents.

  • Most of compounds had potent activity against dermatophyte strains.

  • Compound 4d was the most potent compound against T. interdigitale, T. veruccosum and M. fulvum (MICs = 0.25−2 μg/ml).

  • 3D-structure of the target protein (tubulin) was modeled by homology modeling and used for docking and MD simulations.

Abstract

A series of indole-derived methoxylated chalcones were described as anti-dermatophyte agents. The in vitro antifungal susceptibility testing against different dermatophytes revealed that most of compounds had potent activity against the dermatophyte strains. In particular, the 4-ethoxy derivative 4d with MIC values of 0.25−2 μg/ml was the most potent compound against Trichophyton interdigitale, Trichophyton veruccosum and Microsporum fulvum. Moreover, the 4-butoxy analog 4i displaying MIC values in the range of 1−16 μg/ml had the highest inhibitory activity against Trichophyton mentagrophytes, Microsporum canis, and Arthroderma benhamiae. To predict whether the synthesized compounds interact with tubulin binding site of dermatophytes, the 3D-structure of target protein was modeled by homology modeling and then used for molecular docking and molecular dynamics (MD) simulation studies. Docking simulation revealed that the promising compound 4d can properly bind with tubulin. The molecular dynamics analysis showed that interactions of compound 4d with the active site of target protein have binding stability throughout MD simulation. The results of this study could utilize in the design of more effective antifungal drugs with tubulin inhibition mechanism against keratinophilic fungi.

Introduction

The dermatophytes, as members of the family Arthrodermataceae, are filamentous and keratinophilic fungi causing dermatophytosis, a superficial mycosis of the keratinized tissues such as skin, nail, hair, claws, hoof and horn (Martinez-Rossi et al., 2017; Abastabar et al., 2013). There are more than 40 species of dermatophytes in three genera, Microsporum, Epidermophyton and Trichophyton which affected 20–25 % of population worldwide (Baghi et al., 2016; Zhan and Liu, 2017). Infections caused by dermatophytes are predominantly acquired by direct contact with infected humans and animals as well as sources of contagion such as soil, toenail clippings, bedding, toilet seats, showers, wrestling mats, swimming pools and locker rooms (Allizond et al., 2016; Murmu et al., 2015; Segal and Frenkel, 2015). Dermatophytosis, in addition to being a cosmetic problem, is considered as important public health and economic issues, which impact on the quality of life in millions of people annually (Ayanlowo and Oladele, 2014).

Currently, terbinafine and itraconazole are treatments of choice for various forms of dermatophyte infections (Gupta and Cooper, 2008). It is documented that terbinafine has a very broad spectrum antifungal activity and well-absorption following oral dosing with at least 80 % bioavailability (Katz, 1999). However, resistance to terbinafine and other inhibitors of squalene epoxidase has been reported in Trichophyton rubrum isolates (Mukherjee et al., 2003). Also, azole resistance among fungal pathogens is an increasing concern in recent years, thus more efforts are required in antifungal drugs discovery with appropriate safety (Hashemi et al., 2015).

Microtubules are essential components of cytoskeleton which involved in different functions including mitosis, intracellular transport, cell division and etc. There are various antimitotic agents that disrupt tubulin binding site and inhibit tubulin polymerization. Benzimidazoles (carbendazim, thiabendazole) and griseofulvin, act as microtubule-targeting drugs which used to treat fungal infections (Chatterji et al., 2011; Carlson, 2008).

Chalcones (1,3-diaryl-2-propen-1-ones) and their derivatives are one of the most important types of natural products that obtained from both synthetic and natural sources (Mirzaei and Emami, 2016; Mirzaei et al., 2017a). They are precursors for the flavonoid family and represent a wide range of chemotherapeutic activities, including anticancer (Aryapour et al., 2012; Letafat et al., 2013; Ketabforoosh et al., 2014), antileishmanial (Nazarian et al., 2010; Foroumadi et al., 2010), and antibacterial activities (Nowakowska, 2007; Mahapatra et al., 2015). In particular, several studies have indicated that chalcone analogues have antifungal properties (Sato et al., 1994; Sivakumar et al., 2009; Lopez et al., 2001; Batovska et al., 2007; Boeck et al., 2005). López et al. reported that chalcones with different substituents on rings A and B are active against dermatophytes and not against another group of fungi (Lopez et al., 2001). An important strategy for finding new bioactive chalcones is replacement of aryl ring with different heterocycles including indole ring. Recently we designed and synthesized a series of indole-chalcones as new analogs of chalcones (Fig. 1) (Mirzaei et al., 2017b,c). Thus we describe here, the antifungal evaluation of them as potent anti-dermatophyte agents and their molecular modeling study.

Section snippets

Fungi isolates

The fungal strains including Candida albicans, Candida glabrata, Candida tropicalis, Aspergillus fumigatus, Penicillium chrysogenum, Trichophyton interdigitale, Trichophyton veruccosum, Trichophyton mentagrophytes, Microsporum fulvum, Microsporum canis, Arthroderma benhamiae, and Epidermophyton floccosum originated from patients or environments have been identified using morphological features, Polymerase Chain Reaction Restriction Fragment Length Polymorphism (PCR-RFLP) and PCR-sequencing of

Chemistry

The target chalcone derivatives 2-4 were synthesized by a Claisen-Schmidt condensation of 3-acetyl indole 1a-c and appropriate substituted benzaldehyde derivatives in the presence of LiOH as catalyst (Scheme 1) (Mirzaei et al., 2017a,b). All compounds were obtained as (E)-isomer as evidenced from large coupling constants of vinylic hydrogens in 1H NMR spectra.

Antifungal activity

The antifungal activity of chalcones compounds 2-4 was evaluated against different fungal strains (Abastabar et al., 2014, 2016;

Conclusion

In conclusion, we have introduced a series of indole-derived methoxylated chalcones as anti-dermatophyte agents. The in vitro antifungal susceptibility testing against different dermatophytes revealed that most of compounds had potent activity against the dermatophyte strains. In particular, the 4-ethoxy derivative 4d with MIC values of 0.25−2 μg/ml was the most potent compound against T. interdigitale, T. veruccosum and M. fulvum. Moreover, the 4-butoxy analog 4i displaying MIC values in the

Declaration of Competing Interest

The authors report that they have no conflicts of interest.

Acknowledgment

This work was supported by a grant (No. 1173) from the Research Council of Mazandaran University of Medical Sciences, Sari, Iran.

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