Synthesis, 3D-QSAR and Molecular Docking Study of Nopol-Based 1,2,4-Triazole-Thioether Compounds as Potential Antifungal Agents.

Xiu Wang,Baoyu Li,Guishan Lin,Fuhou Lei,Wengui Duan,Ming Chen

doi:10.3389/fchem.2021.757584

Abstract

Cytochrome bc 1 complex is an important component of cellular respiratory chain, and it is also an important target enzyme to inhibit the growth of plant pathogens. Using cytochrome bc 1 complex as the target enzyme, twenty-three novel nopol-based 1,2,4-triazole-thioether compounds were designed and synthesized from natural preponderant resource β-pinene, and their structures were confirmed by FT-IR, NMR, ESI-MS and elemental analysis. The in vitro antifungal activity of the target compounds 5a-5w was preliminarily evaluated against eight plant pathogens at the concentration of 50 µg/ml. The bioassay results showed that the target compounds exhibited the best antifungal activity against Physalospora piricola, in which compounds 5b (R= o-CH3 Ph), 5e (R= o-OCH3 Ph), 5h (R= o-F Ph), 5m (R= o-Br Ph), 5o (R= m,m-OCH3 Ph), and 5r (R= p-OH Ph) had inhibition rates of 91.4, 83.3, 86.7, 83.8, 91.4 and 87.3%, respectively, much better than that of the positive control chlorothalonil. Also, compound 5a (R= Ph) had inhibition rate of 87.9% against Rhizoeotnia solani, and compound 5b (R= o-CH3 Ph) had inhibition rates of 87.6 and 89% against Bipolaris maydis and Colleterichum orbicala, respectively. In order to develop novel and promising antifungal compounds against P. piricola, the analysis of three-dimensional quantitative structure-activity relationship (3D-QSAR) was carried out using the CoMFA method on the basis of their antifungal activity data, and a reasonable and effective 3D-QSAR model (r 2 = 0.944, q 2 = 0.685) has been established. In addition, the theoretical study of molecular docking revealed that the target compounds could bind to and interact with the site of cytochrome bc 1 complex.

Highlights

Plant diseases caused by phytopathogens have always been one of the main reasons for crop yield reduction, and the use of fungicides is the most critical method to effectively control crop diseases in agriculture (Wang et al, 2017)
Cytochrome bc1 complex (EC 1.10.2.2), known as complex III, is an important component of cellular respiratory chain, as well as a target enzyme used in the development of fungicides owing to Antifungal Activity of Nopol Derivatives its ability to inhibit the growth of plant pathogens (Chen et al, 2016; Cheng et al, 2018)
About twenty cytochrome bc1 complex fungicides have been successfully employed in the world market and more are still being developed according to the statistics from the Fungicide Resistance Action Committee (FRAC, 2021) including flufenoxystrobin, fluoxastrobin, famoxadone, pyrametostrobin and so on

Summary

Introduction

Plant diseases caused by phytopathogens have always been one of the main reasons for crop yield reduction, and the use of fungicides is the most critical method to effectively control crop diseases in agriculture (Wang et al, 2017). About twenty cytochrome bc complex fungicides have been successfully employed in the world market and more are still being developed according to the statistics from the Fungicide Resistance Action Committee (FRAC, 2021) including flufenoxystrobin, fluoxastrobin, famoxadone, pyrametostrobin and so on (http://www.frac.info/ (accessed Aug 12, 2021). These compounds inhibit mitochondrial respiration of plant pathogens by binding at the Qo site of a membrane-bound homodimeric cytochrome bc complex and blocking the generation of adenosine triphosphate (ATP), leading to the inhibition of the energy production which is essential for survival (Wang et al, 2018; Zhu et al, 2019). Some kinds of potential cytochrome bc complex inhibitors were designed and synthesized by Yang research team and some target compounds exhibited good in vitro inhibitory activities against downy mildew and powdery mildew (Wang et al, 2011; Hao et al, 2012; Hao et al, 2015)

Methods

Results

Conclusion