Digestive fate of betalains and phenolics from Opuntia fruits and their interaction with human colonic microbiota in a dynamic in vitro gut model.

Opuntia cactus fruits are abundant in betalains and phenolic compounds, widely recognized for their health-promoting potential, yet studies simultaneously addressing their digestive fate and interaction with human gut microbiota remain limited. This research investigated the gastrointestinal digestion and colonic transformation of phytochemical-rich extracts obtained from three Opuntia varieties (Opuntia stricta var. dillenii whole fruit, Opuntia ficus-indica var. Colorada pulp, and Opuntia ficus-indica var. Blanca Buenavista peel) in a dynamic in vitro gut simulator. Betalain and phenolic compound transformation, microbial composition, short-chain fatty acid (SCFA) and ammonium production, and predicted functional capacity were analyzed. Betacyanins were the most labile compounds, with betanin retaining 46% after gastrointestinal digestion and becoming undetectable from the transverse colon onwards. Betaxanthins showed greater persistence, with indicaxanthin reaching the descending colon (7.66%). Piscidic acid was the most stable phenolic, retaining up to 73% after gastrointestinal digestion and remaining detectable throughout all colonic compartments. Opuntia extracts induced extract- and compartment-dependent modulation of gut microbiota, including increases in Actinobacteriota and Bifidobacteriaceae (up to 22.58 and 22.78%, respectively), and reductions in Desulfovibrionaceae (up to -4.45%). Shifts in Megasphaera and Bacteroides were observed (up to -10.52 and - 23.48%, respectively), while key functional taxa remained stable. All extracts enhanced SCFA production, particularly acetate (13.57-26.12 mM), butyrate (1.82-5.3 mM) and valerate (1.4-5.18 mM), while ammonium levels (11.23-13.08 mM) remained within physiological ranges. Functional prediction analyses associated phytochemical-related pathways with core species, supporting functional microbiota resilience. These findings reinforce the potential of Opuntia-derived phytochemicals to modulate colonic metabolic activity, reinforcing their value as functional ingredients within sustainable food systems.