Design, Synthesis, Phloem Mobility, and Bioactivities of a Series of Phenazine-1-Carboxylic Acid-Amino Acid Conjugates.

Linhua Yu,Min Zhang,Junkai Li,Qinglai Wu,Zongli Yao,Di Huang,Xiang Zhu,Zhihong Xu

doi:10.3390/molecules23092139

Abstract

Developing fungicides with phloem mobility that can be applied to leaves to control root or vascular pathogens has long been desirable. To achieve this goal, an efficient and economical strategy involves introducing an amino acid into the existing highly active parent pesticide molecule. Hence, 12 L-phenazine-1-carboxylic acid (PCA)-amino acid conjugates 4a–l were designed and synthesized via a simple synthetic route. In vitro bioassays results showed that all synthesized compounds 4a–l exhibited certain fungicidal activities against six tested fungi. Compound 4c exhibited relatively good fungicidal activity against Rhizoctonia solani, and the EC50 value was 0.084 ± 0.006 mmol/L. The phloem mobility experiments revealed that introducing an amino acid to PCA could effectively endow PCA with phloem mobility in R. communis L. Among them, nine conjugates were found in phloem sap, and L-PCA-Valine 4d exhibited the highest phloem mobility. Analysis results from the prediction of the Kleier model indicated that an active carrier-mediated mechanism may be involved in L-PCA-amino acid conjugates—a result that needs to be confirmed and complemented with further tests. The current research provides useful data for modifying non-phloem-mobile fungicidal molecules to phloem-mobile types.

Highlights

Developing pesticides with phloem mobility has attracted increasing attention in recent years [1,2,3,4,5].The phloem-mobile pesticides are more economical and efficient because they can be applied to foliage and distributed along with plant growth substances to the site of pathogen infection or damage to control root or vascular diseases of crops [6]
Six phytopathogenic fungi were provided by Institute of Pesticides, Yangtze University, and weed seeds were obtained from Jingzhou, Hubei province, China
Intermediate 2 was treated with the corresponding L-amino acid methyl ester hydrochloride by using excessive triethylamine (5 equiv) as base at 0 ◦ C to produce the conjugates 3a–l [12]

Summary

Introduction

The phloem-mobile pesticides are more economical and efficient because they can be applied to foliage and distributed along with plant growth substances to the site of pathogen infection or damage to control root or vascular diseases of crops [6]. Many structural modification strategies have been used in developing phloem-mobile pesticides [7,8,9,10]. One efficient and economical strategy is to introduce plant growth substrate, such as amino acids or monosaccharides, to the existing highly active parent pesticide molecule [9,10]. The biological activities of these conjugates almost disappeared. The group designed and synthesized a glycinergic-fipronil (GlyF) conjugate by adding an amino acid moiety to fipronil. Linking amino acid can change fipronil into a phloem

Methods

Results

Conclusion