Sambucus nigra flower and berry extracts for food and therapeutic applications: effect of gastrointestinal digestion on in vitro and in vivo bioactivity and toxicity.

The bioavailability of natural compounds should be assessed through different perspectives. Studying the behaviour of the extracts after digestion is often overlooked but is crucial for success in the development of active food ingredients. Thus, the bioaccessibility of S. nigra (flower and berry) extracts after in vitro gastrointestinal digestion and their effect on toxicity and bioactive potential were studied. The flower extract had a higher content of phenolic compounds, like rutin, chlorogenic acid and rosmarinic acid, while in the berry extract, rutin, resveratrol, ferulic acid and chlorogenic acid were the main phenolic compounds. The effect of the non-digested and digested extracts was significantly different on different cell lines. The IC50 of the normal cell line (L929) was the highest, indicating low toxicity. The IC50 of the cancerous cell lines (HeLa and HT29) was lower, particularly the extract obtained from the flower upon digestion. In the presence of an oxidant agent - tbHP, only the berry extract was able to significantly reduce the formation of ROS in the L929 cell line, while in the HeLa cells, all the extracts were able to reduce ROS formation. The in vivo Artemia salina lethality bioassay demonstrated a dose-dependent effect of extracts, and the berry digested extract induced the lowest mortality rate. The promising results obtained on the chemical and biological evaluation of the extracts indicate that the natural compounds isolated from S. nigra by-products can be used as potential ingredients for functional food formulations and/or as bio-therapeutic agents.