Flavonols enhanced production of anti‐inflammatory substance(s) by Bifidobacterium adolescentis: Prebiotic actions of galangin, quercetin, and fisetin

Abstract

The gut microbiota is capable of the bioconversion of flavonoids whereas influences of probiotic anaerobes on the bioactivities of flavonoids and vice versa are still unclear. Here, we investigated functional interactions with respect to the anti-inflammatory activity between flavonols and probiotic bacteria. Ten enteric (6 probiotic and 4 indigenous) bacteria were incubated with flavonols (galangin, kaempferol, quercetin, myricetin, and fisetin) under anaerobic conditions, and the supernatants were assessed for their effects on nitric oxide (NO) production in lipopolysaccaride-stimulated RAW264 cells. Although the conditioned medium from the flavonol mono-culture and almost all of the tested co-cultures failed to inhibit NO production, the medium from the Bifidobacterium adolescentis/flavonols (galangin, quercetin, and fisetin) co-culture highly suppressed NO production. This activity increased during the 1-6 H incubation in a time-dependent manner and was not observed in the co-culture using heat-inactivated B. adolescentis. Interestingly, when the B. adolescentis cell number was increased, the supernatant from the mono-culture of the bacteria showed NO suppression, suggesting that B. adolescentis may produce NO suppressant(s), and flavonols may have a promoting effect. These findings indicate that flavonols have a prebiotic-like effect on the anti-inflammatory activity of B. adolescentis.

Effects of phytochemicals on in vitro anti-inflammatory activity of Bifidobacterium adolescentis

“…25) Although the conditioned media from B. adolescentis mono-cultures failed to suppress NO production by LPS-treated RAW264 cells, media from bacteria co-cultured with quercetin showed a dose-dependent increase in inhibitory activity (Fig. 1A) The initial concentration of quercetin in both monoculture and co-culture media was similarly reduced, and largely disappeared by 1 h (Fig.…”

“…Culture conditioned media were prepared as described. 25) Briefly, B. adolescentis (10 8 cfu/mL) and phytochemicals dissolved in dimethylsulfoxide (DMSO) were incubated in serum and antibiotic-free DMEM at 37°C for 3 h under static and anaerobic conditions [B. adolescentis (with DMSO, final concentration 0.05%) or phytochemical alone as mono-culture; B. adolescentis + phytochemical as co-culture]. The culture media were centrifuged twice, once at 5000 g and once at 15,000 g, each for 3 min at 4°C, and the supernatants were decanted and supplemented with 100 U/mL of penicillin and 100 μg/mL streptomycin.…”

“…Bacteroides, Lactobacillus, and Bifidobacterium) were incubated with flavonols (galangin, kaempferol, quercetin, myricetin, and fisetin) in cell culture medium under anaerobic conditions for 3 h, and the ability of the conditioned media to suppress the inflammatory activity of lipopolysaccharide-stimulated macrophages was assayed. Interestingly, we have found that quercetin, galangin, and fisetin enhanced the anti-inflammatory activity of B. adolescentis, 25) a species of Bifidobacterium present in the large intestines of all age groups, including occasionally in infants. 26) In addition, these compounds were not metabolized to other types of bioactive compounds by the bacteria but appeared to increase the production and/or secretion of anti-inflammatory substance(s) from the bacteria.…”

“…26) In addition, these compounds were not metabolized to other types of bioactive compounds by the bacteria but appeared to increase the production and/or secretion of anti-inflammatory substance(s) from the bacteria. 25) These findings suggested that other combinations of probiotic bacteria and dietary phytochemicals could show unique functional interaction. This study therefore evaluated whether other phytochemicals, as well as glycosides and conjugates, could enhance the anti-inflammatory activity of B. adolescentis, similar to quercetin.…”

“…25) Intestinal anaerobes (e.g. Bacteroides, Lactobacillus, and Bifidobacterium) were incubated with flavonols (galangin, kaempferol, quercetin, myricetin, and fisetin) in cell culture medium under anaerobic conditions for 3 h, and the ability of the conditioned media to suppress the inflammatory activity of lipopolysaccharide-stimulated macrophages was assayed.…”