Ecdysone, bioassay

In insects, ecdysone is secreted from the prothoracic glands (PG) at every moulting and pupal stage. Conversion of ecdysone to 20-hydroxyecdysone occurred in fat body, Malpighian tubules, gut and body wall tissues [189]. Although ecdysone may have direct hormonal effects, it is generally held that ecdysone serves as a prehormone that is converted to 20-hydroxyecdysone which functions as the active hormone. This is because in many bioassay systems, 20-hydroxyecdysone appears to be much more active than ecdysone. 

Hikino, H. (1981) Isolation and bioassay of ecdysones from plants, in Advances in Natural Products Extraction and Isolation of BidogfcaSly Active Compounds (eds S. Natori, N. Ikekawa, and M. Suzuki), Kodansha, Halstead Press Books, Ultimo, NSW, pp. 458-471. 

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