The monoterpene phenols from Mosla chinensis Maxim. exhibit strong inhibitory effect on the fungus causing tea leaf blight

• The extract of Mosley chinensis had broad-spectrum antifungal activity. • The content and activity of thymol were higher than those of carvacrol. • Monoterpene phenols could suppress the development of tea gray blight. • Thymol disrupted the integrity of cell membranes, walls and organelles. Tea gray blight (TGB) is a significant disease that gravely affects tea harvest and quality. Mosla chinensis has been validated to have significant antimicrobial effects and is rich in monoterpene phenols.This paper aims to investigate the inhibitory effects of the monoterpene phenols from M. chinensis on Pestalotiopsis kenyana that causing TGB and their antifungal mechanisms. This study first discovered that the methanol extract of Mosla chinensis (EE) displayed strong antifungal activity against four pathogenic fungi ( Pestalotiopsis kenyana, Neopestalotiopsis Piceana, Pestalotiopsis Rhodomyrtus, and Pestalotiopsis theae ) that cause TGB and other pathogenic fungi, with the strongest toxicity against Pestalotiopsis kenyana (EC 50 : 1.23 mg/mL). HPLC analysis showed that EE is rich in monoterpene phenols, with a higher content of thymol than carvacrol. Furthermore, the antifungal activity results showed that the inhibitory effect of thymol (EC 50 = 24.44 μ g/mL, close to carbendazim's EC 50 = 24.21 μ g/mL) on P. kenyana was stronger than that of carvacrol (EC 50 = 48.07 μ g/mL), and its the inhibitory effect on TGB was also significantly higher than that of carvacrol, indicating that thymol may be the most critical component of EE antifungal activity. The results of physiological and biochemical experiments, microscopic observation, staining with propidium iodide and calcium fluoride white, and chitin content determination indicated that the inhibition of thymol on P. kenyana was related to its damage to the hyphal cell membrane, organelles, and cell wall. The monoterpene phenols of M. chinensis have the potential to develop a new plant-derived fungicides against TGB.