BIFIDOBACTERIUM ANIMALIS SSP. LACTIS BB-12 INCREASES THE BIOACCESSIBILITY OF PHENOLIC COMPOUNDS IN RED PITAYA

Bifidobacteria are part of the gut microbiota and well-known for their beneficial effect in human health. Bifidobacterium animalis ssp. lactis BB-12 (B. lactis BB-12) is a probiotic strain associated with a variety of health-promoting traits. Red pitaya [Hylocereus polyrhizus (Weber) Britton & Rose], also known by dragon fruit, is considered a source of phenolic compounds (PC) with great antioxidant activity. The interaction between PC and Bifidobacterium spp. has received increased attention because through enzymatic activity species from this genera have shown to be able to transform PC into more bio-active and/or available forms (e.g. by glycosylation of polydatin to resveratrol). This study was performed to assess the effects of B. lactis BB-12 metabolism on bioaccessibility of red pitaya PC and the antioxidant activity of the bioaccessible PC under simulated physiological conditions. Samples of red pitaya were pasteurized (63 °C/30 min), cooled to room temperature added with B. lactis BB-12 inoculum (final viable counts 7 log CFU/mL) and incubated at 30 °C for 48 h under anaerobic conditions (fermented red pitaya). Samples without B. lactis BB-12 was assayed as control (non-fermented red pitaya). The bioaccessibility of PC was assessed using a continuous system simulating physiological gastrointestinal conditions (oral, gastric and intestinal phases) coupled with a simulated intestinal barrier (cellulose dialysis membrane 12,000 Da). Mechanical agitation was used to mimic the conditions in each digestive compartment. The PC was identified by High Performance Liquid Chromatography (HPLC) using a chromatograph coupled with a diode arrangement detector and a refractive index detector. RP-C18 column (100×4.6 mm, 3.5µm) and a C18 pre-column (12.6×4.6 mm, 5μm) were used to separate the PC using water and methanol acidified as mobile phases at a flow rate of 0.8 mL/min. The peaks were identified by comparing the retention times obtained with those of standards and the average area was used for PC quantification. The oxygen radical absorbance capacity (ORAC) assay was used to measure the antioxidant capacity of the phenolic compounds available for absorption in the small intestine (bioaccessible). The PC identified in both, non-fermented and fermented red pitaya were syringic, caftaric and caffeic acids, catechin, epigallocatechin gallate, epicatechin, rutin, kaempferol 3-glucoside, quercetin 3-glucoside, procyanidin B1 and procyanidin B2; however contents were generally greater (p<0.05) in non-fermented red pitaya. B. lactis BB-12 increased (p<0.05) catechin and hesperidin contents (p<0.05) while decreased cyanidin 3,5-diglucoside, delphinidin 3-glucoside, rutin, quercetin 3-glucoside, kaempferol 3-glucoside, gallic, syringic and caffeic acids. Chlorogenic acid was detected only fermented red pitaya. B. lactis BB-12 increased (p<0.05) the bioaccessibility of procyanidin B2, catechin and epigallocatechin gallate by 32%, 43% and 200%. The antioxidant activity of the bioaccessible fraction of the fermented red pitaya was up to 2-fold higher (p <0 .05) than the bioaccessible fraction of the non-fermented red pitaya. The results obtained show that B. lactis BB-12 metabolism increases the bioaccessibility of PC in red pitaya, as well as the antioxidant activity of the bioaccessible fraction in this fruit. These findings suggest that B. lactis BB-12 fermentation could be a strategy to produce high-added value red pitaya derived products.