Characterization of Insecticidal Sugar Esters of Petunia

Abstract

The recent finding that leaf surface glycolipids of Petunia × hybrida Hort. plants possess insecticidal activity against sweetpotato whiteflies prompted a search for the specific compounds responsible for this biological activity. Successive liquid chromatographic fractionations of an extract of cuticular chemicals of Petunia plants yielded distinct fractions of two glucose esters and four sucrose esters. These different structural types of sugar esters were identified to be 2,3,4-tri-O-acyl-α- + β-d-glucopyranose, 2,3,4,6-tetra-O-acyl-α- + β-d-glucopyranose, 2,3,4-tri-O-acyl-α-d-glucopyranosyl-β-d-fructofuranoside, 2,3,4-tri-O-acyl-α-d-glucopyranosyl-(6‘-O-acetyl)-β-d-fructofuranoside, 2,3,4,6-tetra-O-acyl-α-d-glucopyranosyl-β-d-fructofuranoside, and 2,3,4,6-tetra-O-acyl-α-d-glucopyranosyl-(6‘-O-acetyl)-β-d-fructofuranoside, where the major acyl constituents were 2-methylbutyryl, hexanoyl, 4-methylvaleryl, and heptanoyl groups. Bioassays of the individual sugar esters against adult sweetpotato whiteflies revealed that the majority of the activity was produced by tri- and tetra-substituted sucrose esters, while highly substituted sucrose or glucose esters were weakly toxic or completely inactive. Keywords: Glucose esters; sucrose esters; Petunia; structures; whitefly pesticides; chromatography; NMR; GC/MS