In vitro assessment of the impact of astragalus, pineapple stem and bergamot extracts on the human fecal microbiota
Botanical extracts are increasingly used in functional foods and supplements, yet their impact on gut microbial ecosystems remains poorly understood. In this study, an Astragalus membranaceus root extract, a pineapple stem extract, and a bergamot extract were evaluated both in native form and after simulated gastrointestinal digestion (INFOGEST protocol) for their effects on human gut bacteria. Antimicrobial activity was first assessed in monocultures of nine commensal bacterial strains, including Lactobacillus acidophilus LA14, Lacticaseibacillus paracasei DG, Hafnia alvei HA4597, Bifidobacterium longum BB536, and Bifidobacterium animalis BL-04. Only minimal, strain-specific inhibition was observed at the highest non-physiological concentration of 100 mg/mL, primarily affecting Akkermansia muciniphila, Bacteroides fragilis, and Collinsella aerofaciens. Subsequently, a stabilized fecal suspension (SFS) model was employed to investigate community-level responses over a 48 h anaerobic incubation. 16S rRNA gene profiling revealed that a-diversity and ß-diversity were not significantly altered by any botanical treatment or digestion status. Minor shifts in specific taxa (most notably a decrease in Collinsella spp. with digested Astragalus extract) were detected, while keystone species such as Faecalibacterium prausnitzii and A. muciniphila remained stable. These findings indicate that, at physiologically relevant doses, the tested botanicals do not compromise overall microbial diversity or deplete essential taxa, supporting their classification as “microbiome-friendly” functional ingredients.