Oleuropein from olive leaf extracts and extra-virgin olive oil provides distinctive phenolic profiles and modulation of microbiota in the large intestine

The interest in the modulation of gut microbiota by polyphenols from olives and derived products is increasing. In this work, phenolic leaf extracts (PLE) were in vitro faecal fermented to evaluate the changes in phenolic profiles and the impact on microbiota, using a commercial extra-virgin olive oil (EVOO) as reference. The in vitro fermentation decreased oleuropein content in PLE, determining an increase of hydroxytyrosol and other phenolic metabolites. An increase (p < 0.05) of hydroxytyrosol (LogFC = 6.02; VIP score = 1.05) was also observed in fermented EVOO. Besides, PLE significantly (p < 0.05) changed amino acids (LogFC = 6.1) and fatty acids (LogFC = 5.9) profile of the faeces. Metagenomic sequencing revealed that Coriobacteriaceae at the family level, and Collinsella at the genus level, were the most affected by PLE fermentation. These findings support the modulation of the gut microbiota exerted by phenolics from PLE and EVOO.

Automated summary

The modulation of gut microbiota by polyphenols from olives and derived products is of increasing interest. In this study, phenolic leaf extracts (PLE) were in vitro fermented to evaluate changes in phenolic profiles and their impact on microbiota. The fermentation of PLE decreased oleuropein content and increased hydroxytyrosol and other phenolic metabolites. A significant increase in hydroxytyrosol was also observed in fermented extra-virgin olive oil (EVOO). The fermentation of PLE also significantly changed the amino acids and fatty acids profile of the faeces. Metagenomic sequencing revealed that Coriobacteriaceae at the family level and Collinsella at the genus level were the most affected by PLE fermentation.