Design, Synthesis, and Biological Activity of Novel Laccase Inhibitors as Fungicides against Rice Blast
Tengda Sun, Xiaoyu Jin, Xiaoming Zhang, Xingxing Lu, Changkai Wang, Jialin Cui, Huan Xu, Xinling Yang, Xili Liu, Li Zhang, Yun Ling
Abstract
Laccase is a potential target for novel agricultural fungicide discovery. PMDD-5Y was the first agent reported with high activity against laccase to control phytopathogenic fungi. Thirty-two novel agents containing cinnamaldehyde thiosemicarbazide were synthesized with PMDD-5Y as the lead compound, with most of the target compounds exhibiting excellent activity in vitro. Compound a2 (EC50 = 9.71 μg/mL) exhibited greater potency against Magnaporthe oryzae than the commercial fungicide isoprothiolane (EC50 = 18.62 μg/mL). The curative and protective effects of a2 against M. oryzae on rice were more than those of PMDD-5Y. Scanning electron microscopy indicated that a2 could cause mycelial growth atrophy and malformation. Furthermore, a2 (IC50 = 0.18 mmol/L) showed higher activity against laccase than PMDD-5Y (IC50 = 0.33 mmol/L) and cysteine (IC50 = 0.30 mmol/L). Molecular docking analysis revealed the nature of interaction between these compounds and laccase. This research identified a novel laccase inhibitor a2 as a fungicide candidate to control rice blast in agriculture.