Biotransformation of Opuntia stricta var. dillenii extracts by human gut microbiota: evolution of betalains and phenolic compounds, and formation of secondary metabolites

Opuntia stricta var . dillenii cactus fruits are abundant in betalains and phenolic compounds, widely recognized for their bioactive properties. The present study investigates the microbial transformation of these bioactives from O. dillenii extracts, obtained by environmentally friendly techniques, after exposure to human gut microbiota under controlled batch colonic fermentation conditions. To discern microbiota-specific effects, parallel incubations were conducted under identical abiotic conditions. Results showed that key compounds, including betacyanins, phenolic acids, and flavonoids, underwent extensive microbial degradation. Untargeted metabolomic analysis further revealed the formation of several secondary metabolites, including L-tyrosine, dihydroferulic acid, gentisic acid, and opuntiol, primarily in microbiota-active incubations. In contrast, compounds like tyramine, ferulic acid, and caffeic acid were more prevalent under abiotic conditions, indicating alternative, non-microbial transformation mechanisms. These results underscore the significant role of gut microbiota in modifying the chemical profile of natural extracts, providing new insights into the metabolic pathways of betalains and phenolic compounds from cactus fruits, and leading to the formation of secondary metabolites. • Biotransformation by gut microbiota extensively modifies Opuntia stricta var. dillenii bioactives. • Potentially new bioactive compounds emerge through microbial metabolism. • Abiotic compared to microbial conditions yield different metabolite profiles. • In vitro batch fermentation provides insights into the metabolic pathways of cactus fruit bioactives.