Ultraviolet (UV) radiation is associated with the development of extrinsic skin aging. We performed in vivo assays in order to investigate the protective effect of a combination of grapefruit and rosemary extracts (cG&Re) on UVB-induced skin aging. The results indicated that cG&Re displayed elastase inhibitory activity in a dose-dependent manner. Topical application of cG&Re mitigated photo-aging related lesions such as skin erythema and thickening in photo-aged BALB/c mice dorsal skin, by preventing UVB-induced collagen degradation. Immunohistochemical analyses revealed that cG&Re stimulated SIRT-1 expression, and suppressed MMP-1 and IL-1β expression. It was observed that expression of MMP-1 and -13 mRNA was downregulated in the cG&Re-treated group. Furthermore, cG&Re treatment drastically suppressed protein expression of MMP-1 and regulated the phosphorylation of p-38 kinase. As expected, oral administration of cG&Re resulted in the same SIRT-1, MMP-1, and IL-1β expression patterns observed upon topical application of cG&Re in the UV-induced mice model. Overall, the current results demonstrated that cG&Re attenuated both the downregulation of MMP-1 expression and up-regulation of SIRT-1 expression, as well as decreased phosphorylation of MAPK in UVB-induced skin ageing mice model, suggesting that cG&Re might be used as an internal food ingredient for beauty-purposes as well as a functional food material.

Abstract
Introduction
Materials and Methods
    Sample Preparation and HPLC Analysis
    Elastase Inhibition Assay
    Cell Culture and Cell Viability Assay
    UVB-Irradiated Cell Viability Assay
    Mice UVB-Induced Models
    Measurement of Skin Thickness, Erythema Level, and Transepidermal Water Loss (TEWL)
    Histochemical Analysis
    RNA Isolation and Reverse Transcription-Polymerase Chain Reaction (RT-PCR)
    Western Blot Analysis
    Statistical Analysis
Results
    HPLC Profile of cG&Re
    Effect of cG&Re on Elastase Inhibitios
    Effect of cG&Re on Cell Viability
    Effects of cG&Re on UVB-induced Mice Skin
    Effect of cG&Re on Histochemical Changes
    Effects of cG&Re on mRNA and Protein Expression of Skin Aging-Related Biomarkers
    Protective Effects of Orally Administered cG&Re on Skin Tissues
Discussion
References

• Hee-Jeong Choi(School of Food Science & Biotechnology, Kyungpook National University)
• Md Badrul Alam(School of Food Science & Biotechnology, Kyungpook National University)
• Peijun Zhao(School of Food Science & Biotechnology, Kyungpook National University)
• Yeong-Ho Cha(School of Food Science & Biotechnology, Kyungpook National University)
• Tae-Ho Kim(Biomedical Research Institute, Kyungpook National University Hospital)
• Sang-Han Lee(School of Food Science & Biotechnology, Kyungpook National University) Corresponding author