Evaluating the efficacy of natural deep eutectic solvents in biocontrol of Alternaria alternata

Abstract

The excessive and widespread use of synthetic fungicides has raised numerous environmental and health-related concerns. In response, there has been a growing global interest in the use of natural plant-derived products for plant protection. A promising area of research in this field is the development of natural deep eutectic solvents (NADES). These solvents, composed of natural compounds, offer a sustainable alternative for extracting bioactive compounds from plants, thereby enhancing the effectiveness of natural pesticides and antimicrobial agents. This study aimed to evaluate the efficacy (E%) of different NADES based on menthol, thymol, and camphor. Antifungal activity was tested against Alternaria alternata. Due to volatility of terpenoids, the experiment was conducted in the vapour phase in Petri plates. The incubation lasted seven days at 26 ± 1 degree Celsius, with the plates sealed and covered with parafilm.  At the end of the experiment (7th day), the diameter of A. alternata mycelium was measured, and the inhibition percentage was calculated into E%. Among the menthol-based NADES, Menthol:Thymol stood out with an E% ranging from 58-100%, while for the thymol-based NADES, Thymol:Caprylic acid achieved an inhibition of 52-100%. However, the camphor-based NADES did not reach 100% efficacy. Such studies are crucial for selecting NADES that could be used for the biocontrol of A. alternata, offering a potentially sustainable alternative to synthetic fungicides.