Chemical composition, skin microbiota metabolism, antimicrobial potential and anti-inflammatory properties of witch hazel bark (Hamamelis virginiana L.)

Abstract

Ethnopharmacological relevance The bark of witch hazel (Hamamelis virginiana L.) has been employed in traditional medicine primarily due to its astringent properties, which are attributed to the tannins it contains. It has been utilized to alleviate the symptoms of haemorrhoids, inflammation of the skin and mucous membranes, and minor wounds. However, the potential changes in the chemical composition and biological activity of witch hazel bark extract following incubation with skin microbiota have not yet been analysed. Aim of the study The objective of the study was to isolate and identify the principal components of the H. virginiana bark extract and monitor the alterations occurring during incubation with the skin microbiota ex vivo. Subsequently, the activity of the extract, its isolated compounds, and the primary metabolite was evaluated to determine their potential for alleviating skin cell inflammation, promoting wound healing, and exhibiting antibacterial effects. Materials and methods The composition of the extract and the identification of metabolites following incubation with ex vivo skin microbiota were conducted using UHPLC-DAD-ESI-IT-MS. The principal components isolated by preparative HPLC were identified on the basis of their NMR spectra. Biological studies were conducted on human neutrophils ex vivo, stimulated with f-MLP (ROS production) and LPS (IL-1β, CXCL-8 and TNF-α secretion), as well as on HaCaT keratinocytes stimulated with TNF-α/IFN-γ and on fibroblasts (NHDF) stimulated with lipoteichoic acid (IL-6 and CXCL-8 release). The most potent samples were subjected to an in vitro wound healing assay, along with testing for their ability to inhibit the growth of Staphylococcus aureus. Results The extract and hamamelitannin exhibited the most pronounced anti-inflammatory activity. Conversely, the principal metabolite generated during incubation with the skin microbiota, ellagic acid, was observed to stimulate the release of inflammatory mediators, particularly by fibroblasts. In the in vitro wound healing assay, both the extract and hamamelitannin supported migration of keratinocytes to the site of injury, with hamamelitannin demonstrating significantly stronger activity. The minimal inhibitory concentration for S. aureus growth was determined to be 0.5 mg/mL for the extract and 0.5 mM for hamamelitannin. Furthermore, both the extract and hamamelitannin were observed to prolong the lag phase and doubling time of the species. Conclusion The aqueous extract of Hamamelidis cortex, along with its key component, hamamelitannin, has been identified as a promising agent with anti-inflammatory and wound-healing properties. Nevertheless, the extract and its components may undergo chemical modifications due to the metabolism of the skin microbiota potentially leading to changes in biological activity with undesirable consequences.