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Cholesterol is a well-known component in fats of animal origin and it also is the precursor of natural hormones. Phytosterols appear in plants and only differ slightly in structure from cholesterol. An important difference however is the low absorption in the gut of phytosterols and their saturated derivatives, the phytostanols. As a result, there is time for all kind of reactions in faecal material inside and outside of the gut. Determination of the abuse of natural hormones may be based on gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Abuse of natural hormones changes the 13C/12C ratio of some metabolites during a relatively long time. The formation of (natural) hormones in the gut may interfere with this method. Designer drugs are mainly known from sports doping. In animal fattening, designer drugs may be used as well. Small changes in the structure of (natural) hormones may lead to a new group of substances asking for new strategies for their detection and the constatation of their abuse.

Abstract: Current evidence suggests that neo formation of the anabolic steroid boldenone (androsta-1,4-diene-17-ol-3-one) occurs in calves’ faecal material, making it difficult to distinguish between illegally administered boldenone and its potential endogenous presence. This strengthens the urgent need to elucidate the pathway leading to boldenone formation. In our laboratory, the invertebrate Neomysis integer (Crustacea, Mysidacea) was used since 2004 as an alternative model for the partial replacement of vertebrate animals in metabolisation studies with illegal growth promotors and veterinary drugs, e.g. boldenone. The present study evaluates the metabolic capacity of other invertebrates, the brine shrimp Artemia franciscana and maggots of the greenbottle fly Lucilia sericata. The first results indicate that maggots of L. sericata are able to convert phytosterols and –stanols, nowadays in substantial amounts added to animal feed, into androsta-1,4-diene-3,17-dione (ADD), the precursor of boldenone, at a yield of 0.10–0.14% (p <0.001, significance compared to endogenous excretion of maggots) but not to boldenone itself. Furthermore, β-testosterone, an endogenous hormone, was transformed into androst-4-ene-3,17-dione (AED), ADD and β-boldenone at a significant (p <0.001, significance compared to endogenous excretion of maggots) yield of circa 13%, 0.80% and 2.2%, respectively. In future studies these results are of value to further evaluate the use of maggots of L. sericata as an invertebrate model in metabolisation studies. [Copyright &y& Elsevier]