Dietary alkaloids

Some male arctiid moths produce their courtship pheromone from dietary pyrrolizidine alkaloids acquired during feeding by the larvae [ 126]. Conversion of monocrotaline to hydroxydanaidal by males is accomplished by aromatiza-tion, ester hydrolysis and oxidation of an alcohol to the aldehyde [7]. In the case of Utetheisa ornatirx the stereo-configuration at C7 of the dietary alkaloid is the same as the pheromone released (R). In contrast, another arctiid, Creatono-tos transiens, can convert a dietary precursor alkaloid with the (S) configuration at C7 (heliotrine) to (l )-hydroxydanaidal. The biosynthesis occurs by first oxidation-reduction at C7 to convert the stereochemistry and then proceeds through aromatization, hydrolysis, and oxidation [7]. 

There exists evidence that some insects store dietary alkaloids derived from natural sources. Figure 98 presents insect species that are known to accumulate pyrrolizidine alkaloids during different developmental stages. The larvae and adults of these insects can metabolize pyrrolizidine alkaloids in current physiological activities. These alkaloids are not toxic for these organisms. Moreover, there is observed trace accumulation of a portion of these compounds in the liver. There is no definitive purpose for these traces. Generally, the opinion presented in 1888 by Stahl in Germany that the accumulation of alkaloids is for defensive purposes has been most often cited in the research literature. 

However, in the case of dietary alkaloids, it would seem that more than only traces of alkaloids, which do not exhibit selective toxicity to antagonist organisms, would be needed for defensive purposes. These trace alkaloids probably have a role in the organism s metabolism, development and behaviour. The traces of alkaloids in the eggs of Arctia caja also suggest a potential participation of these compounds in reproduction. Moreover, attention should be given to the fact that alkaloids are dietary sequestrations acquired from feeding on plants. 

Davenport, J. W. and Conner, W. E. (2003). Dietary alkaloids and the development of androconial organs in Estigmene acrea. Journal of Insect Science 3 3. 

Schmitz, B., Buck, M., Egelhaaf, A. and Schneider, D. (1989). Ecdysone and a dietary alkaloid interact in the development of the pheromone gland of a male moth ([Creatonotos, Lepidoptera Arctiidae). Roux s Archives of Developmental Biology 198 1-7. 

Conner, W. E., Eisner, T Vander Meer, R. K Guerrero, A. and Meinwald, J. (1981). Precopulatory sexual interaction in an arctiid moth (Utetheisa matrix), role of a pheromone derived from dietary alkaloids. Behavioral Ecology and Sociobiology 9 227-235. 

CONNER, W.E., EISNER, T., VAN DER MEER, R.K., GUERRERO, A., MEIN WALD, J., Precopulatory sexual interactions in an arctiid moth (Utetheisa omatrix) Role of a pheromone derived from dietary alkaloids. Behav. Ecol. Sociobiol., 1981,9,227-235. 

The larvae of the blue butterfly (Plebejus icaroides) feed only on lupines, rich in alkaloids. As far as we know, the larvae do not sequester or store the dietary alkaloids (506). Helopeltis feeds on Cinchona bark, which is rich in cinchonine-like alkaloids it stores and uses them for its own defense (506). Larvae of the butterflies Pachlioptera aristolochiae, Zerynthia po-tyxena, Ornithoptera priamus, and Battus philenor live on Aristolochia plants and were shown to take up and sequester aristolochic acid, a carcinogenic alkaloid discussed earlier, as an effective defense compound (4,28,236). 

Daly JW, Secunda SI, Garraffo HM, et al. (1994) An uptake system for dietary alkaloids in poison frogs (Dendrobatidae). Toxicon 32 657-663. 

There is evidence that some insects store dietary alkaloids derived from natural sources. Figure 4.3 presents insect species that are known to accumulate pyrrolizidine alkaloids during different developmental stages. The larvae and adults of these insects can metabolize pyrrolizidine alkaloids in current physiological activities. These alkaloids are not toxic for these organisms. 

Hantak MM, Grant T, Reinsch S, Mcginnity D, Loring M, ToyookaN, et al. Dietary Alkaloid Sequestration in a poison frog and experimental test of alkaloid uptake in Melanophryniscus stelzneri (Bufonidae). J Chem Ecol 2013 39(ll-12) 1400-6. 

Besides avoiding, some insects can tolerate the defense chenustry of their host. The potato beetle Leptinotarsa decemlineata) lives on Solanum species containing steroidal alkaloids, which are tolerated but not stored by this species. The bruchid beetle, Bruchidius villosus, predates seeds of QA rich plants, such as Laburnum anagyroides. This beetle eliminates most of the dietary cystisine with the faces. Certain aphids can store the dietary alkaloids, for example, QA in Aphis cytisorum, A. genistae, and Macrosiphum albifrons and PA in Aphis jacobaeae and A. cacaliaster [70]. 

Thoms, C Ebel, R., Hentschel, U and Proksch, P. (2003) Sequestration of dietary alkaloids by the spongivorous marine mollusk Tylodina perversa. Z. Natuiforsch. C. Biosci., 58, 426-432. 

Ebel, R., Marin, A., and Proksch, P. (1999) Organ-spedes distribution of dietary alkaloids in the marine opisthobranch Tylodina perversa. Biochem. Syst. Ecol, 29, 989-999. 

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