Acaricidal and insecticidal efficacy of new esters derivatives of a natural coumarin osthole

To discover non-food bioactive natural-product-based pesticides for crop protection, new osthole esters ((2'-E)-4'-(isoxazolin-5 -yl)carbonyloxyosthole derivatives) containing the isoxazoline fragment were constructed by structural modification of a natural coumarin osthole isolated from Cnidium monnieri. The configurations of three compounds were confirmed by X-ray crystallography. Their agricultural activities were evaluated against two typically crop-threatening pests Mythimna separata Walker and Tetranychus cinnabarinus Boisduval. Against T. cinnabarinus, compounds 4 (LC50: 0.75 mg/mL) and 5h (LC50: 0.76 mg/mL) displayed >= 1.5-fold acaricidal activity of osthole and good control effects in the greenhouse. Against M. separata, compounds 5a (final mortality rate (FMR): 55.1%), 5c (FMR: 62.0%), and 50 (FMR: 55.1%) at 1 mg/mL showed 1.5-1.6 folds growth inhibitory activity of osthole. It suggested that introduction of the acryloyloxy group at the C-4' position of osthole was important for insecticidal and acaricidal activities, and compound 4 can be further structurally modified as pesticidal agents.

Automated summary

New osthole esters containing the isoxazoline fragment were constructed by modifying a natural coumarin osthole, and their agricultural activities against two pests were evaluated. Some compounds showed high insecticidal and acaricidal activities, and the introduction of the acryloyloxy group was found to be important for activity.