Phytochemical composition and antifeedant activity of five Vincetoxicum taxa against Spodoptera littoralis and Leptinotarsa decemlineata

Five Vincetoxicum taxa (V. canescens subsp. canescens, V. canescens subsp. pedunculata, V. fuscatum subsp. fuscatum, V. fuscatum subsp. boissieri and V. parviflorum) were investigated for insect antifeedant activity against Spodoptera littoralis and Leptinotarsa decemlineata. At a dose of 500 μg/cm2, 12 extracts were 100 % feeding deterrent, while 6 extracts showed 86.3- 99.3 % antifeedant activity. The effective doses (ED50) of the total ethanol extract from V. canescens subsp. pedunculata and of the methanol: dichloromethane (1:1) extract from V. parviflorum were 12, and 18 μg/cm2, respectively, against S. littoralis, and that of the total ethanol extract from V. fuscatum subsp. fuscatum was 25 μg/cm2 against L. decemlineata. The dichloromethane extracts of V. parviflorum and V. canescens subsp. pedunculata inhibited the growth of S. littoralis with ED50 values of 0.08 and 0.09 mg/g, respectively, and their LD50 values for larval mortality were 1.07 and 1.03 mg/g, respectively. Phytochemical analysis revealed the presence of cardiotonic glycosides, sugars, flavonoids and alkaloids in all investigated taxa. In the dichloromethane and methanol:dichloromethane (1:1) extracts, phenanthroindolizidine alkaloids were detected by LC/MS/MS.