The genus Bifidobacterium is well known to have beneficial health effects. We discovered that quercetin and related polyphenols enhanced the secretion of anti-inflammatory substances by Bifidobacterium adolescentis. This study investigated characteristics of the anti-inflammatory substances secreted by B. adolescentis. The culture supernatant of B. adolescentis with quercetin reduced the levels of inflammatory mediators in activated macrophages. Spontaneous quercetin degradant failed to increase anti-inflammatory activity, while the enhancement of anti-inflammatory activity by quercetin was sustained after washout of quercetin. Physicochemical treatment of the culture supernatant indicated that its bioactive substances may be heat-stable, non-phenolic, and acidic biomolecules with molecular weights less than 3 kDa. Acetate and lactate have little or no effect on nitric oxide production. Taken together, the anti-inflammatory substances secreted by B. adolescentis may be small molecules but not short chain fatty acids. In agreement with these findings, stearic acid was tentatively identified as a bioactive candidate compound.
Keywords: BAD, Bifidobacterium adolescentis with DMSO; BAQ, B. adolescentis with quercetin; Bifidobacterium adolescentis; DMEM, Dulbecco’s modified Eagle’s medium; DMSO, dimethyl sulfoxide; ELISA, enzyme-linked immunosorbent assay; FBS, fetal bovine serum; IL-1β, interleukin 1β; LC-MS, liquid chromatography-mass spectrometry; MW, molecular weight; NO, nitric oxide; PGE2, prostaglandin E2; QUE quercetin; TNF-α, tumor necrosis factor-α; anti-inflammatory activity; bioactive substances; culture supernatant; iNOS, inducible nitric oxide synthase; quercetin.