Structure-Antifungal Activity Relationship of Fluorinated Dihydroguaiaretic Acid Derivatives and Preventive Activity against Alternaria alternata Japanese Pear Pathotype

Abstract

The structure-activity relationship of the antifungal fluorinated dihydroguaiaretic acid derivatives was evaluated. Some of the newly synthesized lignan compounds were found to show higher antifungal activity against phytopathogenic fungi such as Alternaria alternata (Japanese pear and apple pathotypes) and A. citri than the lead compound, 3-fluoro-3'-methoxylignan-4'-ol (3). The broad antifungal spectrum of 3'-hydroxyphenyl derivative 16 was observed, and the 3'-fluoro-4'-hydroxyphenyl derivative 38 was found to show the highest activity against the A. alternata Japanese pear pathotype, with an EC value of 11 μM. The preventive effect of the potent lignan on the infection of A. alternata in the Japanese pear's leaves was also shown.

Searching for the Stereoisomer of 7,7′-Epoxylignan Showing the Most Potent Antifungal Activity and Finding the 3-(Trifluoromethyl)-4-hydroxy-3′-fluoro Derivative to Have the Highest Activity

“…Lignano-9,9′-lactone 43 was 163 and 6 times less potent than the corresponding 9,9′-epoxylignan 38 against A. alternata and C. lagenarium , respectively. On the contrary, the activities of synthesized 9,9′-epoxylignans 33–37 and 41 were almost the same as that of previously synthesized butane type lignans bearing both a hydroxy group and a halogen atom in the benzene ring . In this study, the applications of CF 3 38 enhanced the activity.…”

“…On the contrary, the activities of synthesized 9,9′-epoxylignans 33−37 and 41 were almost the same as that of previously synthesized butane type lignans bearing both a hydroxy group and a halogen atom in the benzene ring. 44 In this study, the applications of CF 3 38 enhanced the activity. This suggests that both the 9,9′-epoxylignan structure and the CF 3 group play an important role in obtaining higher activity.…”

Regiospecific and Enantiospecific Effects of the β-Benzyl-α-benzylidene-γ-butyrolactone Structure on Phytotoxic Fungi

“…The synthetic methods of (8 R ,8′ R )- 13 and (8 S ,8′ R )- 13 are shown in Supporting Information. Since butane and tetrahydrofuran type lignans have been effective against the A. alternata Japanese pear pathotype and C.…”

Discovery of rosin‐based acylhydrazone derivatives as potential antifungal agents against rice Rhizoctonia solani for sustainable crop protection

“…In compounds 4a – 4p , the antifungal effect of compounds with a benzene ring structure attached to the thiophene ring was higher than in compounds without the benzene ring structure ( 4l – 4p > 4a – 4k ), and the antifungal effect of compounds with halogen atoms attached to the benzene ring was higher ( 4n – 4p ). This may be due to the introduction of aromatic ring and electron‐withdrawing groups to enhance the induction and conjugation effect of the dehydroabietyl acylhydrazone compounds, increasing the electron transfer rate from the donor to the acceptor and thus improving the antifungal effect 29–31 …”

“…This may be due to the introduction of aromatic ring and electron-withdrawing groups to enhance the induction and conjugation effect of the dehydroabietyl acylhydrazone compounds, increasing the electron transfer rate from the donor to the acceptor and thus improving the antifungal effect. [29][30][31] 3.3 Effect of dehydroabietyl acylhydrazone (4n) on the cell membrane permeability of R. solani The relative conductivity of R. solani was increased remarkably after treatment with compound 4n compared to the control, which indicates mycelium electrolyte leakage (Fig. 1(b)).…”