Gut microbiota metabolism and the permeability of natural products contained in infusions from herb of European goldenrod Solidago virgaurea L.

Ethnopharmacological relevance: Solidago virgaurea L. (also known as European goldenrod) is a pharmacopoeial plant material popularly used by patients in the form of an infusion. It was traditionally used in Europe and North America for the treatment of urinary tract conditions. It is also reported as a topical agent for skin disorders. Aim of the study: Gut microbiota metabolism plays a crucial role in the bioavailability of natural products contained in plant extracts taken orally. The aim of the current study was to establish the biotransformation of compounds contained in an infusion from goldenrod using human and piglet fecal microbiota in vitro. The permeability of unmetabolized natural products and gut microbiota metabolites was evaluated using a Caco-2 cell model. Preliminary anti-inflammatory assays of raw extract using human neutrophils were also established. Material and methods: An infusion was prepared from Solidaginis virgaureae herba commercially available on the market. The characterization of the raw extract was performed by UHPLC-DAD-MS method. The infusion was incubated with human or swine fecal samples in anaerobic conditions. Metabolism products were analyzed and identified by UHPLC-DAD-MS technique. The permeability of the natural products contained in the raw infusion and after metabolism was checked by UHPLC method. The influence of raw extracts on proinflammatory functions of human neutrophils after LPS stimulation was established by flow cytometry and ELISA. Results: The experiments showed that goldenrod infusion contains mainly caffeoylquinic acid derivatives, flavonoids, and some phenylpropanoids. Natural products present in the extract were transformed by human and swine microbiota to smaller molecules mainly phenylpropanoid acid derivatives. The permeability assays showed that most of the parental compound present in the infusion cannot cross the gut epithelial barrier. In contrast, metabolites were able to cross the Caco-2 monolayer. Depending on the structure, different possible mechanisms of transport were observed. The infusion did not significantly influence the proinflammatory functions of human neutrophils. Conclusions: Following oral administration of goldenrod infusion, phytochemicals are prone to undergoing metabolism by gut microbiota to smaller phenylpropionic acid derivatives that can be bioavailable after crossing the gut epithelial barrier to be further metabolized and distributed. Detected metabolites should be considered as potentially active compounds responsible for the bioactivity of the raw plant material in vivo.

Automated summary

Goldenrod is a traditional medicinal plant used in Europe and North America for urinary tract and skin disorders. Research shows that compounds in goldenrod infusion can be metabolized by human and swine gut microbiota into smaller phenylpropionic acid derivatives with better permeability through the gut epithelial barrier.