Valorization of the Photo-Protective Potential of the Phytochemically Standardized Olive (Olea europaea L.) Leaf Extract in UVA-Irradiated Human Skin Fibroblasts

Abstract

Leaves of Olea europaea are a by-product of the olive oil industry and a dietary supplement with acknowledged antioxidant and anti-inflammatory activity but underestimated photoprotective potential. We investigated the protective effects of the LC-PDA-MS/MS standardized ethanol-water extract of olive leaves (OLE), containing 26.2% total phenols and 22.2% oleuropein, with underlying mechanisms against the UVA-induced oxidative damage in human dermal fibroblasts. Hs68 cells were pre-treated (24 h) with OLE (2.5–25 μg/mL) or the reference antioxidants, quercetin and ascorbic acid (25 μg/mL), followed by irradiation (8 J/cm2). OLE significantly reduced the UVA-induced DNA damage and reactive oxygen species (ROS) overproduction and increased the thioredoxin reductase (TrxR) expression and post-radiation viability of fibroblasts by inhibiting their apoptosis. Both intrinsic and extrinsic apoptotic signaling pathways appeared to be inhibited by OLE, but the activity of caspase 9 was the most reduced. We hypothesized that the TrxR up-regulation by OLE could have prevented the UVA-induced apoptosis of Hs68 cells. In addition, a significant decrease in UVA-induced secretion levels of tumor necrosis factor (TNF-α) and interleukin-2 (IL-2) was shown in human lymphocyte culture in response to OLE treatment. In summary, our results support the beneficial effect of OLE in an in vitro model and indicate its great potential for use in the cosmetic and pharmaceutical industry as a topical photoprotective, antioxidant, and anti-inflammatory agent.

Comparative Study of the Efficacy of EHO-85, a Hydrogel Containing Olive Tree (Olea europaea) Leaf Extract, in Skin Wound Healing

“…That is supported by previous results from our group, showing that OELE protects dermal fibroblasts in vitro against oxidative stress induced by hydrogen peroxide [28]. Also, other studies have shown the ability of OELE to act as a photoprotective, anti-inflammatory, and antioxidant agent in dermal fibroblasts when exposed to ultraviolet irradiation [53]. In addition, some studies indicate that oleuropein, which, as discussed above, is the most abundant polyphenol in OELE, has positive effects on fibroblasts.…”

Oleuropein-Rich Gellan Gum/Alginate Films as Innovative Treatments against Photo-Induced Skin Aging

“…Previous studies have demonstrated the protective role that OLE exerts against oxidative stress in UV-irradiated cells [21,36,37], and these are now further supported by our results that demonstrate the antioxidant activity of the developed materials using the DPPH assay (see Figure 5b).…”

Characterization of the Metabolic Profile of Olive Tissues (Roots, Stems and Leaves): Relationship with Cultivars’ Resistance/Susceptibility to the Soil Fungus Verticillium dahliae

“…Acetoxypinoresinol glucoside was the most abundant lignan in most cultivars, with contents ranging from 494 to 1588 mg kg −1 DW in stems, and 262 to 1001 mg kg −1 DW in roots. The absence of this family of compounds in olive leaves has been widely documented in other works dealing with the LC-MS phenolic profiling of leaves [41,54,55], while other authors have reported very low levels of lignans in this olive tissue [30,39,56].…”