Sesquiterpene lactones larvae

Molan, A. L., Duncan, A. J., Barry, T. N. and McNabb, W. C. (2003). Effects of condensed tannins and crude sesquiterpene lactones extracted from chicory on the motility of larvae of deer lungworm and gastrointestinal nematodes . Parasitology International, 52, 209-218. 

A number of sesquiterpenes have been demonstrated to have pronounced biological activity ( ) among the non-volatile compounds the sesquiterpene lactones are best known (M) but other oxygenated sesquiterpenes are also known to be active. For example, the role of gossypol, a dimeric sesquiterpene and structurally related compounds has been investigated (21,22). The oxygenated sesquiterpenes, shiromodiol monoacetate and diacetate, from Parabenzoin trilobum (=Lindera triloba Blume) possess potent anti feeding activity toward Spodoptera litura larvae (85). 

The growth of eridania larvae was significantly reduced by sesquiterpene lactones added to their diet. Two sesquiterpene lactones were used in these tests 8 (3 -sarracinoyloxycumambranolide (8 6 SC) from Helianthus maximillani (18) and desacetyleupasserin from H, mollis (13) (Figure 3). These compounds were added to an artificial diet at concentrations of 0.1% and 1.0% and fed to fifth instar larvae of S eridania. At a concentration of 1.0%, both compounds caused significant growth inhibition (Table 1). Both compounds are present in Helianthus leaves at levels of 1-5%. 

Larvae of S eridania were also subjected to preference tests to see if they would avoid ingesting sesquiterpene lactones if given the choice of feeding on treated or untreated food. Starved fifth instar larvae were simultaneously presented with bean leaves (Phaseolus vulgaris) coated with a 1% acetone solution in which a sesquiterpene lactone had been dissolved and bean leaves coated with solvent only. After 24 hours, leaves coated with 8 6 SC showed significantly less feeding than the solvent-coated controls, but larvae showed no preference between controls and leaves coated with desacetyleupasserin (Table 2). 

Table 1. Effect of two Hellanthus sesquiterpene lactones on the growth of eridania larvae. ...

Sesquiterpene lactones were added to artificial diets at concentrations indicated. Ten early fifth instar larvae were raised on each concentration. Gain in weight was measured daily for each individual. Negative numbers indicate average weight loss for larvae in that group. 

Table 2. Feeding deterrence of two Helianthus sesquiterpene lactones to S. eridanla larvae. ...

Acetone solutions of each sesquiterpene lactone were coated on bean leaves. Control leaves were coated with solvent only. Starved fifth instar larvae were given a choice of feeding on control or treated leaves. Tests of each compound against a control were repeated with ten larvae. 

How might young Hj electellum larvae obtain pollen Before the florets open, the pollen is produced and stored in the anthers. To reach the pollen in an unopened floret, larvae must crawl or eat their way into the floret and then eat into the anthers. The sesquiterpene lactone-containing glandular trichomes on the anther tips seem to be situated in just the right location to prevent the larvae from reaching the pollen (Figure 4). 

Sesquiterpene lactones from Parthenium species were strongly inhibitory to growth of larvae of Helicoverpa zea and Spodoptera exigua (Isman and Rodriguez, 1983). Tenu-lin (111), the major sesquiterpene lactone of Helenium amarum, imparts a bitter taste to milk and is toxic to livestock. Helenalin (112) from Helenium microcephalum is toxic to several mammalian species in oral doses as low as 85 fjLg/kg. Hymenoxys odorata, from which a toxin, hymenovin... 

Despite the usual antifeedant or toxic effects observed with other insects, larvae of the sunflower moth Homoesoma electellum, Lepidoptera Pyralidae), a specialist on species of sunflower (Helianthus), are able to feed on flower parts that contain appreciable amounts of sesquiterpene lactones (Gershenzon and Croteau, 1991). 

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