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The fronds of the brown alga Eisenia bicyclis are regarded as healthy foods and are used as skin care agents because they are rich in dietary fibres, minerals, and antioxidant compounds. However, E. bicyclis stems have been overlooked thus far. In this study, we determined the in vitro antioxidant and antiglycation properties of E. bicyclis stems and their dietary effects on mice fed a high-sucrose and low-fibre diet. The total phenolic content, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity, ferric-reducing power, and antiglycation activity of the E. bicyclis stem-aqueous extract solution were higher than those of the fronds. The diet containing 5% (w/w) dried E. bicyclis stems increased excretion frequency and faecal and caecal weight and decreased plasma cholesterol levels. The abundance of Bacteroidaceae family and Akkermancsia muciniphila-, Bacteroides acidifaciens-, Phocaeicola vulgatus-, and Parabacteroides goldsteinii-like bacteria increased in E. bicyclis stem-fed mice. These results suggested that E. bicyclis stems could be a source of functional foods and cosmetic products.

Background Red chilli pepper ( Capsicum annuum ; RP) is a popular spice containing the active compound capsaicin. Indigenous gut bacteria and metabolism can affect host health. The functions of capsaicin, including the regulation of metabolic health and anti-oxidant properties, may be correlated with the gut microbiota. Methods To identify indigenous gut bacteria that are responsive to RP, Institute of Cancer Research mice fed a diet with no fibre or with 5% (w/w) RP for 14 days. Additionally, human stool samples collected from four healthy volunteers were incubated without (control) or with 2% (w/v) RP at 37 °C for 24 h. Microbiota in murine caecal samples and human faecal cultures were analysed using 16S rRNA (V4) amplicon sequencing. Results Compared with the microbiota in mice fed no-fibre diets, Lachnospiraceae spp.-, Muribaculaceae spp.-, and Phacaeicola vulgatus -like bacteria were defined as murine RP-responsive indigenous gut bacteria (RP-RIB). In the human faecal cultures, acetate and propionate levels were higher in RP cultures than in the control cultures. Subdoligranulum spp.-, Blautia spp.-, Faecalibacterium prausnitzii -, P. vulgatus- , and Prevotella copri -like bacteria were defined as human RP-RIB. Compared with control culture Fe-reducing power was increased in the culture with RP. Conclusion RP increases the amount of short-chain fatty acid–producing bacteria and beneficial gut bacteria in mouse and human faecal cultures. Overall, RP could have a positive effect on the host by altering the gut microbiota.

Background Turmeric ( Curcuma longa ; TM) is widely used as a spice and possesses anti-inflammatory, antioxidant, and antibacterial properties. The relationship between TM functions and gut microbiota is still unclear. Methods and results To investigate the effect of TM on gut microbiota and to identify indigenous gut bacteria that are responsive to TM, we fed Institute of Cancer Research mice a diet containing either no fibre (NF, n  = 6) or 5% (w/w) TM ( n  = 6) for 14 days. Moreover, we obtained human stool samples from four healthy volunteers and incubated the samples without (control) or with 2% (w/v) TM at 37 °C for 24 h. Subsequently, microbiota analysis in murine caecal samples and human faecal cultures was performed using 16S rRNA (V4) amplicon sequencing. Higher faecal weights ( p  < 0.01) and lower plasma triacylglycerol levels ( p  < 0.05) were measured in the TM-fed mice than in the NF-fed mice. Furthermore, TM feeding increased the abundance of butyrate-producing and other short-chain fatty acid (SCFA)-producing bacteria in mice as well as in human faecal cultures, and Roseburia bacteria were detected as TM-responsive indigenous gut bacteria (TM-RIB) both in mice and in human faecal cultures. Lastly, in the case of human faecal cultures, SCFA contents and antioxidant properties were higher in TM cultures than in control cultures ( p  < 0.05). Conclusion TM appears to hold the potential to positively affect the host by altering the gut microbiota. Further studies are required to clarify the synergistic effects of TM and TM-RIB.

Outbreaks of algal blooms for Sargassumhorneri and Ulva spp., called golden and green tides on the South Korean coast, severely damage the local coastal environment and marine ecological system. However, these edible algae are natural resources of beneficial bioactive components, such as dietary fibres, phenolic compounds, and minerals. In this study, the antioxidant and anti-glycation properties of 2% aqueous extract solution (AES) in vitro from S.horneri (Sh) and Ulvapertusa (Up), and the effects of dried S.horneri and Up on the caecal microbiota of mice fed a high-sucrose and low-fiber diet were investigated. Total phenolic content, antioxidant activity (DPPH radical scavenging and Fe-reducing power), and anti-glycation activity in the BSA-fructose model were higher in Sh-AES than in Up-AES groups. Male Institute of Cancer Research (ICR) mice fed a 5% (w/w) S.horneri diet for 14 days showed a reduced increase in body weight. 16S rDNA (V4) amplicon sequencing results showed that the ratio of Firmicutes/Bacteroidota was reduced after S.horneri and U.pertusa intake. Faecalibaculumrodentium-, Akkermansiamuciniphila-, and Roseburiaintestinalis-like bacteria were enriched in the S.horneri group. Phocaeicolavulgatus-like bacteria were abundant in both the S.horneri and U.pertusa groups. In contrast, the prevalence of Clostridiumdisporicum-like bacteria was low in mice fed the S.horneri diet. Among the bacteria enriched after S.horneri and U.pertusa administration, P.vulgatus was found to be prevalent. From these results, S.horneri from golden tides may be useful as a functional food.

Ecklonia cava subsp. kurome (EK) and E. cava subsp. stolonifera (ES) are rich in phlorotannins and water-soluble polysaccharides (alginates, laminarans and fucoidans). Total phenolic content (TPC), antioxidant (O2− radical scavenging and Fe-reducing) and anti-glycation (bovine serum albumin-fructose model) capacities of dried EK and ES were higher than those of Eisenia bicyclis and Eisenia nipponica in vitro (p < 0.05). To clarify the effect of EK and ES on gut microbiota, 5% (w/w) EK or ES was administered to Institute of Cancer Research mice fed a high-sucrose and low-dietary fibre diet for 14 days and their caecal microbiota was analysed using 16S rDNA (V4) amplicon sequencing. The amplicon sequence variant (ASV) numbers of the EK and ES groups were 4- and 2-fold lower than those of the no fibre (NF) diet group. Bacteroidota containing alginate- and laminaran-degrading microbes, such as Bacteroides acidifaciens- and B. intestinalis-like bacteria, were more abundant in EK and ES groups than in the NF group. Faecalibaculum rodentium- and Akkermansia muciniphila-like bacteria were also more abundant in EK and ES groups than in the NF group. These EK- and ES-responsive indigenous gut bacteria have been regarded as beneficial commensal for host health. Further studies on EK and ES including investigation of dose-dependent effects are needed.

The holdfast of Saccharina japonica (SjH) is a by-product of kombu cultivation and is rich in dietary fibres and phenolic compounds. SjH is regarded as a functional food material with anti-infection, immunomodulatory, and anti-viral effects. In this study, we aimed to examine SjH-responsive indigenous gut bacteria (SjH-RIB) in Institute of Cancer Research (ICR) mice fed a diet containing either no fibre or 5% (w w −1 ) SjH for 14 days. Additionally, we sought to determine the effects of SjH on organic acids, putrefactive compounds, and microbiota in human faecal cultures. Human stool samples collected from five healthy volunteers were incubated without (control) or with 2% (w w −1 ) SjH at 37 °C for 24 h. The microbiota in murine caecal samples and human faecal cultures were analysed via 16S rRNA (V4) amplicon sequencing. Compared to the mice fed no-fibre diets, mice fed SjH showed high caecal levels of Clostridium sensu stricto 1 -, Oscillospiraceae spp.-, Parabacteroides spp.-, and Alistipes spp.-like bacteria. In contrast, Allobaculum , a dominant genus in the no-fibre group, was not detected in the SjH group. In human faecal cultures, the levels of acetate and propionate were higher in SjH-cultures than in the control cultures ( p  < 0.05). Furthermore, SjH-cultures showed low phenol contents. The genera Bacteroides , Faecalibacterium , and Bifidobacterium were more abundant in SjH-cultures than in the control cultures, although the abundance of each amplicon sequence variant in the SjH-RIB genera varied among individuals. These results suggest that the functions of SjH might be correlated with altered gut microbiota composition. Graphical Abstract