Locusta migratoria alkaloids

The glucose mimic, desoxynojirimycin (38) (fvomMorus, mulberry, Moraceae), inhibits a-glucosidases in the manuna-lian gut. A mannose analog, desoxymannojirimycin (39), inhibits mannosidases. Another alkaloid from Derris (Fabaceae) inhibits the action of invertase but does not prevent hydrolysis of this disaccharide in the mammalian gut. In artificial diets with Locusta migratoria, 0.001% of DMDP in the... 

It should also be remembered that the defensive role of alkaloids in host protection is probably not as simple as the presence or absence of a single functional group on an alkaloid or even whether the alkaloid is in the host plant at all. In many cases, there may be additive effects of feeding deterrent compounds based on the entire chemical composition of the host plant. For example, when the alkaloids nicotine and tomatine, each of which have been shown to exhibit feeding deterrences of 25%, were fed in artificial diets to Locusta migratoria the overall feeding deterrence was approximately 50% (19). In this case the alkaloids acted in an additive fashion to produce a more effective chemical defensive mechanism. Adams and Bernays (19) went on to show that this additive characteristic of feeding deterrence was not restricted to alkaloids but was equally effective with alkaloids and various combinations of phenolics, terpenoids, and other miscellaneous secondary plant compounds. 

In a broad spectrum feeding study, which included some steroidal alkaloids as well as many other secondary plant products, an oligophagous locust, Locusta migratoria, was offered more than 100 different plants as food material. Most dicots, which contained higher quantities of alkaloids, were rejected and monocots were by far the preferred food source. Extracts of the rejected dicots inhibited feeding of artificial diets while extracts from the monocots did not affect feeding of the artificial diets (2). Of more than 100 chemicals which were added to artificial diets to test effectiveness as a feeding deterrent, alkaloids and monoterpenoids were consistently the most effective at the lowest concentrations. The alkaloids which were tested in this study were as shown in Table 2.2. 

Table 2.2. Comparison of alkaloid concentrations in the plant and in artifical diets on the feeding deterrency of Locusta migratoria.

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