Repair effect and underlying mechanisms of volatile components/essential oil from Perilla frutescens leaves on the skin barrier.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaves of Perilla frutescens (L.) Britt. have long been topically used in Asian folk medicine to alleviate inflammatory and allergic skin disorders. Modern pharmacology confirms its anti-inflammatory, antioxidant, anti-allergic and skin-repairing activities. Nevertheless, the volatile active ingredients and molecular mechanisms of perilla leaves for skin-protective effects remain unclear. This work represents the first systematic stratified investigation comparing epidermal barrier repair between perilla leaf essential oil (PLEO) and its major constituent perillaldehyde, integrating in-silico prediction and in-vitro validation to dissect the multi-terpenoid synergistic mechanism of PLEO. AIM OF THE STUDY: This study aimed to clarify the protective effect and molecular mechanism of perilla leaf essential oil (PLEO) and its major component perillaldehyde on the skin barrier, and to identify the superiority derived from multi-component synergism by comparing their differential efficacy in restoring epidermal structural and functional integrity. MATERIALS AND METHODS: The chemical composition of PLEO was characterized via gas chromatography-mass spectrometry (GC-MS). Human adult low-calcium high-temperature keratinocytes (HaCaT) were used as the in vitro model. Cell Counting Kit-8(CCK-8), scratch wound healing, tight junction immunofluorescence, epidermal lipid quantification, qPCR, Western blot and other assays were performed to assess the skin-barrier-protective effects of PLEO and its major constituent perillaldehyde and to preliminarily explore their regulatory mechanisms. Network pharmacology and molecular docking were further applied to predict core targets and signaling pathways, providing complementary mechanistic evidence for the in vitro observations. RESULTS: GC-MS identified 30 components accounting for 99.28% of total constituents, with perillaldehyde (45.89%,420 mg/g in PLEO), limonene (28.42%), and β-caryophyllene (10.32%) as the predominant compounds. Non-cytotoxic working concentrations were ≤50 μg/mL for PLEO and ≤21 μg/mL for perillaldehyde. PLEO significantly accelerated migration of injured HaCaT keratinocytes, achieving a wound-healing rate of 79.64% ± 3.21% after 48 h treatment at 25 μg/mL; this value was significantly higher than the effect produced by concentration-matched perillaldehyde (p < 0.01). Both PLEO and perillaldehyde markedly up-regulated epidermal structural genes (LOR, IVL, FLG, LCEs) by 1.5- to 2.3-fold relative to the injury-model group (p < 0.05), restored intercellular lipid homeostasis, and activated the PI3K/Akt and MAPK signaling pathways by increasing the phosphorylation level of key pathway proteins without changing total-protein abundance. PLEO dose-dependently up-regulated tight-junction proteins Claudin-1 and Occludin (maximum 2.1-fold, p < 0.01). By contrast, perillaldehyde only increased Claudin-1 expression and failed to induce Occludin up-regulation. Network-pharmacology analysis screened 70 overlapping targets and 28 core hub genes associated with skin-barrier repair. Molecular-docking simulations confirmed stable binding affinities (binding energies ≤ -6.0 kcal/mol) between five core terpenoid ingredients and hub target proteins. Among them, caryophyllene oxide displayed the strongest binding affinity toward PIK3CD (-8.1 kcal/mol) and PTGS2 (-7.8 kcal/mol). CONCLUSION: Beyond the effect of single perillaldehyde, PLEO (25 μg/mL) exerts superior barrier-protective benefits attributed to synergistic interactions among diverse terpenoid constituents. It activates PI3K/Akt and MAPK signaling and restores epidermal structural integrity. These findings validate the traditional skin-protective usage of Perilla frutescens and indicate that PLEO serves as a promising natural topical agent for the prevention and treatment of skin barrier dysfunction.