ecdysteroids

Ecdysteroids are a class of polyhydroxylated steroid compounds that act as hormones in arthropods and occur as phytoecdysteroids in plants. The most common member is 20-hydroxyecdysone (20E), with ecdysone serving as a prohormone that can be converted to 20E. They are widespread in animals, especially insects, as well as in many plant species.

In insects, ecdysteroids regulate growth, molting, and metamorphosis. They are produced mainly in the prothoracic glands and released in pulses that trigger molt and developmental transitions. The hormonal signal is perceived by the ecdysone receptor (EcR) and its partner USP, forming a transcriptional complex that controls the expression of genes involved in development. The outcome of a molt is influenced by juvenile hormone levels, which determine whether the insect molts to another larval stage or proceeds to metamorphosis.

Plants also contain ecdysteroids, referred to as phytoecdysteroids. These compounds are thought to function as defense chemicals that deter herbivores and pathogens. Their structural similarity to insect ecdysteroids means they can disrupt insect development when ingested, although they typically exhibit low activity in vertebrates.

Biosynthesis involves the conversion of cholesterol through a series of enzymatic steps. In insects, cytochrome P450 enzymes mediate hydroxylation and oxidation to yield ecdysone and 20E. In plants, sterol-derived pathways generate phytoecdysteroids via distinct, plant-specific routes. The precise roles and receptors for ecdysteroids in non-insect organisms are less conserved, and vertebrates generally show low receptor affinity.

Human use and safety: 20E and related compounds are marketed in some regions as dietary supplements for athletic performance and muscle growth. Robust clinical evidence is limited, and regulatory status varies. They are typically considered to have low toxicity in humans, but systematic evaluation and long-term safety data are ongoing. Research continues into ecological roles, pest management applications, and potential biomedical uses.