EFSA Project on the use of NAMs to explore interspecies metabolic differences on essential oils as feed additives

Botanical preparations, such as essential oils are increasingly used as feed additives to improve the feed quality and animal health while reducing antibiotic use. Regarding safe usage of these preparations for both humans and relevant animal species (e.g., food-producing animals and pets), the toxicity of their constituents requires to be characterised. Particularly, p-allylalkoxybenzene derivatives, that are present in certain botanical preparations, are known to be both genotoxic and carcinogenic and raise health concerns. However, little is known about species differences in sensitivity to the biological effects of these compounds, nor on the transfer from feed to food. Moreover, toxicokinetic properties and resulting toxicity of these compounds can be influenced by other substances present in the botanical preparations. Narrowing this knowledge gap, a NAM-based approach was carried out for five representative p-allylalkoxybenzenes: elemicin, estragole, methyleugenol, myristicin and safrole for six model species: cat, chicken, cow, human, pig and rat. The aim was to generate in vitro kinetic data from liver S9 incubations to explore potential species differences in bioactivation of p-allylalkoxybenzenes combined with PBK modelling. The influence of terpenoids on the p-allylalkoxybenzene-bioactivation was investigated in parallel. In vitro bioactivation was observed in all species for phase I and phase II metabolism at the species and compound-specific level. The presence of terpenoids revealed to be of minor influence on the p-allylalkoxybenzene-bioactivation. The PBK model simulations for two p-allylalkoxybenzenes revealed that all species have a relatively higher formation of the 1’-sulfooxy metabolite compared to that in rats (differences exceed the default uncertainty factor of 4). PBK model simulations of excretion/deposition of the p-allylalkoxybenzenes and their related 1’-hydroxy metabolite indicated limited transfer into milk, eggs and edible tissues. This case study demonstrates the applicability of NAMs to identify species differences in the metabolism of natural compounds from botanical preparations in support of risk assessment.