# Design, Synthesis, Antibacterial, and Antifungal Evaluation of Phenylthiazole Derivatives Containing a 1,3,4-Thiadiazole Thione Moiety

## TL;DR

This study designed and tested new phenylthiazole compounds with strong antibacterial and antifungal properties against plant pathogens.

## Contribution

The paper introduces novel phenylthiazole derivatives with enhanced antibacterial and antifungal activities against plant pathogens.

## Key findings

- Compound 5k showed excellent antibacterial activity against Ralstonia solanacearum with an EC50 of 2.23 μg/mL.
- Compound 5b exhibited strong antifungal activity against Sclerotinia sclerotiorum with an EC50 of 0.51 μg/mL.
- Electron-withdrawing groups at specific benzene ring positions improved antibacterial and antifungal activities.

## Abstract

To effectively control the infection of plant pathogens, we designed and synthesized a series of phenylthiazole derivatives containing a 1,3,4-thiadiazole thione moiety and screened for their antibacterial potencies against Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, as well as their antifungal potencies against Sclerotinia sclerotiorum, Rhizoctonia solani, Magnaporthe oryzae and Colletotrichum gloeosporioides. The chemical structures of the target compounds were characterized by 1H NMR, 13C NMR and HRMS. The bioassay results revealed that all the tested compounds exhibited moderate-to-excellent antibacterial and antifungal activities against six plant pathogens. Especially, compound 5k possessed the most remarkable antibacterial activity against R. solanacearum (EC50 = 2.23 μg/mL), which was significantly superior to that of compound E1 (EC50 = 69.87 μg/mL) and the commercial agent Thiodiazole copper (EC50 = 52.01 μg/mL). Meanwhile, compound 5b displayed the most excellent antifungal activity against S. sclerotiorum (EC50 = 0.51 μg/mL), which was equivalent to that of the commercial fungicide Carbendazim (EC50 = 0.57 μg/mL). The preliminary structure-activity relationship (SAR) results suggested that introducing an electron-withdrawing group at the meta-position and ortho-position of the benzene ring could endow the final structure with remarkable antibacterial and antifungal activity, respectively. The current results indicated that these compounds were capable of serving as promising lead compounds.