Skin is constantly exposed to external irritants like UV rays, IR, harsh surfactants, and retinoids—all of which can compromise the barrier, increase transepidermal water loss (TEWL), and trigger inflammation through pathways such as NF-κB and MAPKs. This study investigated the anti-inflammatory and barrier-restoring effects of Nephelium lappaceum (rambutan) peel extract and geraniin, its major polyphenol compound, known for immunomodulatory properties. Often discarded as waste, this fruit peel may offer a cost-effective natural solution for skin irritation.
Methods
Researchers used both lab-based and clinical methods. Human keratinocytes (HaCaT cells) were stimulated with UV, IR, retinoic acid, SLS, and LPS, and treated with the extract and geraniin. In the clinical phase, a 2% rambutan peel extract cream was applied to human skin before and after irritation. TEWL and skin redness were measured to evaluate skin barrier recovery.
Key Findings
- Both the extract and geraniin significantly reduced expression of inflammatory cytokines in vitro.
- Topical application of the 2% extract reduced TEWL and redness after exposure to UV, retinol, SLS, IR, and physical stripping.
- In retinol-induced irritation, the extract improved TEWL by 46.52% and redness by 35.22% over 14 days.
- Pre-treatment also provided protection, showing lower TEWL and redness compared to untreated skin after exposure.
- A single use after IR exposure or tape stripping also showed measurable improvements in barrier repair.
This study highlights the potential of rambutan peel extract and geraniin as natural anti-inflammatory agents that restore skin barrier function. Their ability to suppress pro-inflammatory cytokines and reduce TEWL suggests a promising future in skincare products designed to calm and protect irritated skin. While further long-term studies are recommended, these findings provide a strong foundation for sustainable cosmetic development using underutilized botanical resources.
Link to the study: https://www.mdpi.com/2079-9284/12/3/117
