In vitro modulatory effects of colonic microflora by olive oil iridoids.

The Mediterranean diet, rich in fruits, vegetables, and grains as well as olive oil and olives, has been associated with a lower risk of coronary heart disease and cancer. The beneficial role of olive oil has been related to its fatty acid composition and the presence of phenolic compounds. The present research aimed to study the biological activity of some olive oil iridoids, such as hydroxytyrosol and tyrosol, as microbial inhibitors and their in vitro effects on modulation of human intestinal microflora. Among the tested strains, Bifidobacterium longum, Lactobacillus salivarius, and Bacteroides vulgatus showed the highest sensitivity to the tested compounds; however, the inhibitory effect of iridoids seemed to be more effective when a mix of olive oil iridoids, instead of pure hydroxytyrosol, was used. The fermentation experiments showed that olive oil iridoids modulate the intestinal microflora, leading to a higher production of total short chain fatty acids and in particular of butyrate. These are important conditions well known to be associated with a protective effect against colon cancer development.