Characterization and feeding deterrent effects on the aphid, Schizaphis graminum, of some derivatives of the sweet compounds, stevioside and rebaudioside A

The intensely sweet compounds, stevioside 1] and rebaudioside A 2], and 15 of their derivatives, were tested for feeding deterrent activity against the aphid, Schizaphis graminum. Included with these compounds was steviol 4], the aglycone of stevioside and rebaudioside A that was one of the most active compounds in this investigation. Loss of feeding deterrent activity of steviol was observed on acetylation or glycosylation of the C-13 tertiary hydroxy group or on methylation of the C-19 carboxylic acid substituent. In contrast, the antifeedant activity of steviol was not greatly affected by modification of either the C-16 exomethylene group or the C/D-ring junction stereochemistry. 13C-nmr data have been obtained for 12 of the test compounds investigated.