UV B PROTECTANT ACTIVITY AND THE EFFECT OF PLANT EXTRACTS ON THE REGULATION OF HAEM OXYGENASE 1 GENE VIA Nrf2 AND ANTIOXIDANT RESPONSE ELEMENT

Abstract

The exposure of skin to ultraviolet-B (UV-B) radiations leads to DNA damage and excessive production of free radicals which imbalance the redox status of the cell and lead to increased oxidative stress. One of the important pathways in antioxidant defence is the Nrf2-ARE pathway which scavenges the oxidants and maintains the redox homeostasis of the cell. Eugenia caryophylata (clove), Foeniculum vulgare (fennel seed) and Abelmoschus esculentus (okra) has been reported to have high polyphenolic content, antioxidant potential and their medicinal properties are well known in traditional medicine. In the current study, UV-B protective abilities of flavonoids from clove, fennel seed and okra and their role in reducing oxidative stress through Nrf2-ARE pathway was determined in human dermal fibroblast (HDF) cells. Protective ability of flavonoid enriched fractions of clove, fennel seed and okra were studied against UV-B induced cytotoxicity, antioxidant regulation, oxidative DNA damage, intracellular reactive oxygen species (ROS) generation, apoptotic morphological changes and regulation of HO-1 gene through Nrf2-ARE pathway. Results demonstrated that flavonoid enriched fractions exhibited a significant antioxidant potential, flavonoid content and protected against UV-B induced cytotoxicity, depletion of endogenous enzymatic antioxidants, oxidative DNA damage, intracellular ROS production, apoptotic changes and over-expression of Nrf2 and HO-1. The present study demonstrated for the first time that the flavonoid enriched fractions of clove, fennel seed and okra could confer UV-B protection probably through Nrf2-ARE pathway by down-regulating Nrf2 and HO-1. These findings suggested that the flavonoids from clove, fennel seed and okra could potentially be considered as UV-B protectants and can be explored further for its topical application to the area of the skin requiring protection. newline