ABSTRACT
The structure-activity relationship was investigated of compounds isolated from the eggs of Pieris brassicae, the large white cabbage butterfly, and eight synthesized related compounds as oviposition deterrents for this insect. The activity of all compounds was tested in a dual-choice bioassay. The two most active oviposition deterrents for P. brassicae were trans-2- [3-(4-hydroxyphenylpropenoyl)amino]-3,5-dihydroxybenzoic acid [8] and trans-2-[3-(3,4-dihydroxyphenylpropenoyl)amino]-3,5-dihydroxybenzo ic acid [2]. Among members of this compound class, alteration of the substituents of the cinnamic acid part of the molecule affected the oviposition deterrent activity more profoundly than other structural changes. Modification of the anthranilic acid part of the molecule resulted in lower activity.
Subject(s)
Alkaloids/chemistry , Brassica/chemistry , Lepidoptera/physiology , Oviposition/drug effects , Alkaloids/pharmacology , Animals , Female , Structure-Activity RelationshipABSTRACT
Pieris brassicae L. butterflies secrete miriamides onto their eggs. These avenanthramide alkaloids are strong oviposition deterrents when sprayed onto a cabbage leaf. However, these compounds could not be detected in cabbage leaves from which egg batches had been removed two days after deposition and that still showed oviposition deterrency. It was concluded that the miriamides were not directly responsible for the avoidance by females of occupied leaves while searching for an oviposition site. Evidence was obtained that cabbage leaves themselves produce oviposition deterrents in response to egg batches. Fractions containing potent oviposition deterrents could be isolated from surface extracts of leaves from which previously laid egg batches had been removed. The term host marking pheromone that was used previously is not applicable in this case.
ABSTRACT
A method has been developed for the quantitation of the bitter component limonin in grapefruit juice and other citrus juices. The sample clean-up consisted of centrifugation, filtration and a selective, rapid and reproducible purification with a C2 solid-phase extraction column. The limonin concentration was determined by high-performance liquid chromatography on a C18 column with UV detection at 210 nm. A linear response was obtained from 0.0 to 45 ppm limonin. The minimum detectable amount was 2 ng. The minimum concentration which was detected without concentration with good precision was 0.1 ppm. The method was also used for the determination of limonin in different types of oranges, including navel oranges, mandarins, lemons, limes, pomelos and uglis.
