Anti-Inflammatory Activity of Compounds Isolated from Digitalis purpurea L. in TNF-α/IFN-γ-Induced HaCaT Keratinocytes and a Three-Dimensionally Reconstructed Human Skin Model

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disorder affecting 10–20% of the population. In this study, we investigate the anti-inflammatory effect on the skin of eight compounds isolated from Digitalis purpurea L., using tumor necrosis factor-α (TNF-α)/interferon-γ (IFN-γ)-stimulated human keratinocytes (HaCaT cells) and a three-dimensional (3D) reconstructed human skin model. Among the tested compounds, desrhamnosyl acteoside exhibited the most potent activity, significantly reducing the secretion of pro-inflammatory cytokines (IL-6, IL-8) and chemokines (CCL17, CCL22), suppressing the expression of inflammatory proteins, and modulating key signaling pathways, including NF-κB, JAK2/STAT1, and MAPK. Notably, this is the first report demonstrating that desrhamnosyl acteoside simultaneously targets all three pathways, indicating a multi-modal mechanism distinct from conventional single-target approaches. In the 3D skin model, desrhamnosyl acteoside further exhibited barrier-protective effects by downregulating inflammatory mediators and upregulating epidermal differentiation markers such as involucrin and loricrin. These findings reveal a previously uncharacterized phytochemical with dual anti-inflammatory and barrier-restorative activities, supporting its potential as a novel therapeutic candidate for AD and other inflammatory skin diseases.