High Value-Added Application of Natural Plant Products in Crop Protection: Honokiol Monoester/Diester Derivatives Containing the Novel Core Scaffold of Benzodihydrofuran and Their Agricultural Bioactivities and Control Effects

Abstract

To discover new potential botanical insecticides from plant secondary metabolites, a series of new honokiol-type monoester/diester derivatives containing the core scaffold of benzodihydrofuran were synthesized by structural modification of honokiol. Against Mythimna separata Walker, 2-hydroxymethy-5-(2′-(para-chlorobenzoyloxy)-5′-(1″,2″-epoxypropanyl))­phenyl-2,3-dihydrobenzofuran (5) and 2-(2″-chloropyridin-5″-ylcarbonyloxy)­methylene-5-(2′-(2″-chloropyridin-5″-ylcarbonyloxy)-5′-(1″,2″-epoxypropanyl))­phenyl-2,3-dihydrobenzofuran (37) displayed >2.1-fold promising insecticidal activity of the precursor honokiol. Against Aphis citricola Van der Goot, 2-hydroxymethy-5-(2′-(tridecylcarbonyloxy)-5′-(1″,2″-epoxypropanyl))­phenyl-2,3-dihydrobenzofuran (21) (LD50: 0.049 μg/nymph) and 2-(para-fluorobenzylcarbonyloxy)­methylene-5-(2′-(para-fluorobenzylcarbonyloxy)-5′-(1″,2″-epoxypropanyl))­phenyl-2,3-dihydrobenzofuran (31) (LD50: 0.040 μg/nymph) showed 3.5- and 4.3-folds potent aphicidal activity of honokiol (LD50: 0.171 μg/nymph), respectively. Interestingly, 2-(tridecylcarbonyloxy)­methylene-5-(2′-(tridecylcarbonyloxy)-5′-(1″,2″-epoxypropanyl))­phenyl-2,3-dihydrobenzofuran (46) (LC50: 0.186 mg/mL) and 2-(dodecylcarbonyloxy)­methylene-5-(2′-(dodecylcarbonyloxy)-5′-(1″,2″-epoxypropanyl))­phenyl-2,3-dihydrobenzofuran (53) (LC50: 0.159 mg/mL: >6.4-fold of honokiol (LC50: 1.024 mg/mL)) exhibited promising acaricidal activity and control efficiency against Tetranychus cinnabarinus Boisduval. Structure–activity relationships indicated that a specific length of the aliphatic chain is necessary for the agricultural activities of honokiol monoester/diester derivatives, especially for the acaricidal activity of diester derivatives.

Optimization of Osthole as a Pesticide Candidate: Synthesis, Crystal Structures, and Agrochemical Properties of Acrylate Derivatives of Isopropenyl 2,3-Dihydrobenzofurans

“…Therefore, the length of the carbon chain R was very important for the acaricidal activity. These similar relationships were also found in honokiol- and piperine-type esters, with the aliphatic chain showing the acaricidal activity. , …”

“…These similar relationships were also found in honokiol-and piperinetype esters, with the aliphatic chain showing the acaricidal activity. 24,48 Subsequently, 72 h CMRs of some compounds at different concentrations against T. cinnabarinus are presented in Table S1 (see the Supporting Information), and their LC 50 values are shown in Table 3. Compound 40 (LC 50 : 0.165 mg/mL) exhibited 8.3-fold pronounced acaricidal activity of 1 (LC 50 : 1.367 mg/mL), and compounds 38 (R = (CH 2 ) 9 CH 3 ), 39 (R = (CH 2 ) 11 CH 3 ), and 41 (R = (CH 2 ) 15 CH 3 ) displayed 5.7− 6.0-fold acaricidal activity of 1.…”

“…20−23 Moreover, honokiol ester derivatives (C, Figure 1) containing the scaffold of dihydrobenzofuran showed the improved insecticidal activity. 24 Notably, the isopropenyl dihydrobenzofuran skeleton also exists in some biologically active natural products, such as angenomalin 25,26 and rotenone (Figure 1). 27,28 Therefore, we innovatively envisaged whether the benzopyrone skeleton in osthole can be replaced with the dihydrobenzofuran one.…”

Natural products in crop protection: thiosemicarbazone derivatives of 3‐acetyl‐N‐benzylindoles as antifungal agents and their mechanism of action

“…Although chemical intervention showed efficient and economical advantages, phytopathogenic fungi have evolved severe resistance due to the extensive use of chemical fungicides 7 . Therefore, discovery of new candidates for effective management of those agricultural diseases is highly urgent 8,9 …”

“…7 Therefore, discovery of new candidates for effective management of those agricultural diseases is highly urgent. 8,9 Indole (I-1, Fig. 1) occurs in the oil of jasmine, cloves and coal tar, and also exists widely as a putrefaction product from animals' intestines.…”