International Journal of Food Microbiology 362 (2022) 109492 Available online 24 November 2021 0168-1605/© 2021 Published by Elsevier B.V. Antifungal activities of fuoroindoles against the postharvest pathogen Botrytis cinerea: In vitro and in silico approaches Chaitany Jayprakash Raorane 1 , Vinit Raj 1 , Jin-Hyung Lee * , Jintae Lee * School of Chemical Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea A R T I C L E INFO Keywords: Fungal inhibition Tubulin Indoles Microtubule polymerase MD simulation ABSTRACT Botrytis cinerea is a common necrotrophic fungal pathogen, leading cause of gray mold diseases in plants and fruit. Several benzimidazoles are used for controlling B. cinerea-associated infection in fruit and vegetables, but benzimidazoles resistance restricts its further uses. Therefore, it is a need for alternative drugs that control B. cinerea. Indoles are multi-faceted compounds and their structural similarities with antifungal benzimidazoles make them a choice for further investigation. Thus, the main objective of the study was to investigate the antifungal potencies of indoles against B. cinerea and to decipher the molecular mechanism involved. We con- ducted in vitro antifungal assays, fruit assays, and computational studies of interactions between indoles and fungal microtubule polymerase. Of the 16 halogenated indoles examined, 4-fuoroindole, 5-fuoroindole, and 7- fuoroindole (MIC range 2–5 mg/L) were found to be more potent than the fungicides fuconazole and natamycin. Fluoroindoles inhibited or eradicated B. cinerea infections in tangerines and strawberries. Molecular dynamic simulation and density functional theory showed that these fuoroindoles stably interacted with microtubule polymerase. Quantitative structure-activity relationship analyses of halogenated indoles revealed that the presence of a fuoro group in the indole moiety is essential for anti-Botrytis activity. The plausibility of the un- derlying antifungal mechanism was confrmed by in vitro tubulin polymerization. Collective outcomes of this study indicates that fuoroindoles could be used as alternative fungicidal agents against B. cinerea. 1. Introduction Fungi are common plant pathogens and are responsible for huge economic losses during harvesting by causing rot, rust, and wilt diseases in various parts of plants, such as stems, fowers, and fruit. Several species of fungal pathogens, such as Colletotrichum, Alternaria, Botrytis, Monilinia, Lasiodiplodia, Phomopsis, and Botryosphaeria, have been re- ported to cause postharvest infections in plants and fruit (Alkan and Fortes, 2015; Sun et al., 2018; Torres-Ossand´ on et al., 2019; Zhang et al., 2019). Among these, Botrytis cinerea is perhaps the most widely studied necrotrophic fungal pathogen and causes gray mold rot in several economically important crops, fruit, and vegetables pre-and post-har- vest (Bernal et al., 2019; García-Pastor et al., 2020; Hua et al., 2018; Qin et al., 2010). Various fungicides are the main choices for the control of gray mold disease caused by B. cinerea (Dean et al., 2012). However, long-term exposure to these fungicides leads to the development of drug resis- tance. Furthermore, these fungicides have been shown to be serious human and environmental toxins (Verweij et al., 2009). For these rea- sons, novel scaffolds are needed to minimize drug resistance and protect fresh fruit, such as strawberries, oranges, and grapes, from B. cinerea- induced gray mold rot. Over the last fve decades, benzimidazole scaffold containing fun- gicides, such as 7-benomyl, carbendazim, thiophanate-methyl, thia- bendazole, and fubendazole, have been used to treat post-harvest fungal infections. Carbendazim is widely used to control fungal patho- gens pre- and post-harvest and acts by distorting mitotic spindles, which are composed of β-tubulin, a protein required for fungal microtubule/ tubulin dynamics and cytoskeleton formation (Davidse, 1986; Davidse and Flach, 1977; Zhu et al., 2018). While several paclitaxel analogues tend to stabilize microtubules (Hari et al., 2006), the fungicides vinblastine and benzimidazole have destabilizing effects (Davidse, 1986; Hari et al., 2003). Indole and indole derivatives play as an important antibacterial (Lee et al., 2009, 2011, 2012, 2013; Nonomura et al., 1996), antifungal (Manoharan et al., 2018), inter-species bioflm signaling (Lee et al., * Corresponding authors. E-mail addresses: jinhlee@ynu.ac.kr (J.-H. Lee), jtlee@ynu.ac.kr (J. Lee). 1 These authors contributed equally to this work. Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro https://doi.org/10.1016/j.ijfoodmicro.2021.109492 Received 13 June 2021; Received in revised form 7 November 2021; Accepted 20 November 2021