Abstract
The aim of this study was to assess the antioxidant, photoprotective, and antiaging effects of Greek propolis. Propolis was subjected to n-heptane or methanol extraction. Total phenolic/flavonoid content and antioxidant potential were determined in the extracts. Promising extracts were evaluated for their cytoprotective properties using human immortalized keratinocyte (HaCaT) or reconstituted human skin tissue following exposure to UVB. Assessment of cytotoxicity, DNA damage, oxidative status, and gene/protein expression levels of various matrix metalloproteinases (MMPs) were performed. The propolis methanolic fractions exhibited higher total phenolic and flavonoid contents and significant in vitro antioxidant activity. Incubation of HaCaT cells with certain methanolic extracts significantly decreased the formation of DNA strand breaks following exposure to UVB and attenuated UVB-induced decrease in cell viability. The extracts had no remarkable effect on the total antioxidant status, but significantly lowered total protein carbonyl content used as a marker for protein oxidation in HaCaT cells. MMP-1, -3, -7, and -9, monitored as endpoints of antiaging efficacy, were significantly reduced by propolis following UVB exposure in a model of reconstituted skin tissue. In conclusion, propolis protects against the oxidative and photodamaging effects of UVB and could be further explored as a promising agent for developing natural antiaging strategies.
Highlights
Skin comprises the largest organ of the human body and the main barrier protecting the organism from various pathogens and environmental stressors, including ultraviolet radiation (UVR) [1]
The methanolic extracts were submitted to a high-performance thin-layer chromatography (HPTLC) profiling and were evaluated for their cell-free antioxidant activity, while the most promising extracts were further evaluated for their potential antimutagenic and antiaging properties
The twenty derived samples were subsequently screened for their total phenolic content and total flavonoid content (TPC and TFC, respectively)
Summary
Skin comprises the largest organ of the human body and the main barrier protecting the organism from various pathogens and environmental stressors, including ultraviolet radiation (UVR) [1]. UVB radiation causes a spectrum of DNA modifications, with the most prominent being the formation of cyclobutane-pyrimidine dimers (CPD) and 8-hydroxy-20 -deoxyguanosine adducts [4], which have been implicated in photo-induced carcinogenesis [5]. UVB radiation can cause accumulation of reactive oxygen species (ROS) leading to generation of oxidative stress. To this end, ROS can react with a variety of biological macromolecules like proteins, DNA, and lipids, causing their oxidation [6]. Through ROS formation, UVB induces activator protein-1 (AP-1) overexpression along with the upregulation of collagen-degrading enzymes like matrix metalloproteinases (MMPs) [7]
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