Novel, Biocatalytically Produced Hydroxytyrosol Dimer Protects against Ultraviolet-Induced Cell Death in Human Immortalized Keratinocytes

• Published in: Journal of agricultural and food chemistry Vol. 60; no. 46; pp. 11509 - 11517
• Main Authors: Zwane, Refiloe E, Parker, Ayesha, Kudanga, Tukayi, Davids, Lester M, Burton, Stephanie G
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 21.11.2012; Amer Chemical Soc
• Subjects: Agriculture; Agriculture, Multidisciplinary; antioxidant activity; Antioxidants - pharmacology; Apoptosis - drug effects; Apoptosis - radiation effects; Biological and medical sciences; cell death; Cell Death - drug effects; Cell Death - radiation effects; Cell Line, Transformed; Chemistry; Chemistry, Applied; Food industries; Food Science & Technology; free radical scavengers; Fundamental and applied biological sciences. Psychology; Gene Expression - drug effects; Gene Expression - radiation effects; Humans; keratinocytes; Keratinocytes - drug effects; Keratinocytes - metabolism; Keratinocytes - radiation effects; Life Sciences & Biomedicine; oxidative stress; Oxidative Stress - drug effects; Phenylethyl Alcohol - analogs & derivatives; Phenylethyl Alcohol - pharmacology; Physical Sciences; Plant Extracts - pharmacology; Protective Agents - pharmacology; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Science & Technology; trees; ultraviolet radiation; Ultraviolet Rays; Western blotting; UV; Biocatalysis; keratinocytes; antioxidants; reactive oxygen species; HUMAN SKIN; DNA-DAMAGE; ALPHA-TOCOPHEROL; GREEN; PHOTOPROTECTION; INHIBITION; POLYPHENOL OXIDASE; OLIVE OIL; ANTIOXIDANT; HYDROGEN-PEROXIDE; Human; Oxygen; Cell death; Dimer; Antioxidant; Species
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf300883h

Compounds derived from botanicals, such as olive trees, have been shown to possess various qualities that make them function as ideal antioxidants and, in doing so, protect them against the damaging effect of ultraviolet (UV)-derived oxidative stress. The aim of this study was to biocatalytically synthesize a dimeric product (compound II) from a known botanical, 3-hydroxytyrosol, and test it for its antioxidant ability using a human immortalized keratinocyte cell line (HaCaT). 2,2-Diphenyl-picryhydrazyl (DPPH) antioxidant assays showed 33 and 86.7% radical scavenging activity for 3-hydroxytyrosol and its dimer, respectively. The ferric-reducing antioxidant power (FRAP) assay corroborated this by showing a 3-fold higher antioxidant activity for the dimer than 3-hydroxytyrosol. Western blot analyses, showing cells exposed to 500 μM of the dimeric product when ultraviolet A (UVA)-irradiated, increased the anti-apoptotic protein Bcl-2 expression by 16% and reduced the pro-apoptotic protein Bax by 87.5%. Collectively, the data show that the dimeric product of 3-hydroxytyrosol is a more effective antioxidant and could be considered for use in skin-care products, health, and nutraceuticals.