Compendium of the most significant studies with reference to properties, intake, effects.

Machała P, Liudvytska O, Kicel A, Dziedzic A, Olszewska MA, Żbikowska HM. Valorization of the Photo-Protective Potential of the Phytochemically Standardized Olive (Olea europaea L.) Leaf Extract in UVA-Irradiated Human Skin Fibroblasts. Molecules. 2022 Aug 12;27(16):5144. doi: 10.3390/molecules27165144. 

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.

Carrara M, Kelly MT, Roso F, Larroque M, Margout D. Potential of Olive Oil Mill Wastewater as a Source of Polyphenols for the Treatment of Skin Disorders: A Review. J Agric Food Chem. 2021 Jul 7;69(26):7268-7284. doi: 10.1021/acs.jafc.1c00296.

Abstract. Current trends toward naturally occurring compounds of therapeutic interest have contributed to an increasing number of studies on olive oil phenolics in the treatment of diseases with oxidative and inflammatory origins. Recent focus has been on olive oil wastewater, which is richer in phenolic compounds than olive oil itself. In this review, we present findings demonstrating the potential use of olive mill wastewater in dermatology. Particular attention is given to compounds with proven benefits in topical pharmacology: caffeic and ferulic acids, tyrosol and hydroxytyrosol, verbascoside, and oleuropein. The review is divided into different sections: inflammatory skin diseases, microbial effects, wound healing in addition to the antimelanoma properties of olive mill waste phenolics, and their potential in sun protection agents. There is strong evidence to support further studies into the valorization of this abundant and sustainable source of phenolic compounds for use in dermatology and dermo-cosmetic preparations.

Melguizo-Rodríguez L, González-Acedo A, Illescas-Montes R, García-Recio E, Ramos-Torrecillas J, Costela-Ruiz VJ, García-Martínez O. Biological effects of the olive tree and its derivatives on the skin. Food Funct. 2022 Oct 25. doi: 10.1039/d2fo01945k. 

Abstract. The olive tree and its derivatives are of great interest in the field of biomedicine due to their numerous health properties. The aim of the present study was to identify the effects of the use of olive products, extra virgin olive oil (EVOO) and products derived from its extraction, on the skin. Numerous studies have pointed out the protective effect of olive compounds on skin ageing, thanks to their role in the different mechanisms involved in the ageing process, such as reducing oxidative stress, increasing cell viability and decreasing histological alterations. With regard to their photoprotective effect, the olive tree and its fruit contain phenolic compounds which have a protective effect against radiation, such as low ultraviolet absorption and high antioxidant activity, acting as a protective factor against photocarcinogenesis. Similarly, the anti-tumour effects of olives have been studied at the level of the different compounds and extracts obtained from them, and their ability to selectively attack human melanoma cells has been observed. They have also shown antibacterial activity against microorganisms particularly implicated in skin infections, such as Escherichia coli, Candida albicans, Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Pseudomonas aeruginosa and Proteus spp. Likewise, on healthy tissue, they have shown the ability to stimulate growth, migration and the expression of genes involved in cell differentiation, which favours the regeneration of skin wounds. According to the results included in this review, the olive tree and its derivatives could be useful in the treatment of many skin conditions.

Callau M, Jenkins N, Sow-Kebe K, Levivier C, Fameau AL. The Effect of Vegetable Oil Composition on the Structural Properties of Oleogels Based on Behenyl Alcohol/Behenic Acid Oleogelator System. J Cosmet Sci. 2021 Jul-Aug;72(4):399-417. 

Abstract. Recently, we described that the weight ratio (R) between behenyl alcohol (BO) and behenic acid (BA) in sunflower oil effects the textural and structural properties of the oleogel system. One R (7:3) was found as optimal since it led to an enhancement of the oleogel properties for both the hardness and the stability in terms of oil-binding capacity. However, what remains unknown is the effect of other vegetable oils. Therefore, in this study, we aim to test a range of different vegetable oils that are widely used in the cosmetic industry. All the oleogels were prepared by heating together at 85°C the oil and the fatty components under magnetic stirring. After heating, the samples were allowed to cool down quiescently to room temperature without any stirring. The oil properties tested included viscosity, density, and surface tension. The oleogel properties (hardness, oil loss, and gel stability) and their structure as a function of R were characterized at different length scales by coupling optical microscopy, differential scanning calorimetry (DSC), Small-Angle X-ray Scattering (SAXS), and Wide-Angle X-ray Scattering (WAXS) experiments. The same crystal structure evolution determined by SAXS and WAXS as a function of R was observed whatever the oil. In the DSC profiles and optical microscopy pictures, no oil effect was detected. However, our results highlighted two different optimal ratios, giving rise to the best oleogels in terms of stability (oil loss) and hardness as a function of the oil. For sunflower, apricot, and rapeseed oils, R = 7:3 was the optimal ratio, whereas R = 8:2 was the optimal ratio for olive and camelina oil. These observations were correlated with the fatty acid chain length composition of the oil. The results obtained have practical applications for the cosmetic industry since it establishes formulation rules for oleogel systems. Oleogels are based on BO and BA components, which are raw materials widely used for hair and skin applications.Different oils have different fatty acid chain lengths composition and as a result, the ratio between BO and BA needs to be adjusted in order to obtain the best oleogel in terms of texture and stability, which can then be used also to produce oil foams.

C de S Ribeiro B, V de C Faria R, de S Nogueira J, Santos Valença S, Chen L, Romana-Souza B. Olive oil promotes the survival and migration of dermal fibroblasts through Nrf2 pathway activation. Lipids. 2022 Oct 26. doi: 10.1002/lipd.12363.

Abstract. Olive oil has beneficial effects on skin wound healing due to its anti-inflammatory and antioxidant properties; however, the mechanism by which olive oil promotes wound healing is unclear. We evaluated the mechanisms involved in Nrf2 pathway activation by olive oil and its role in cell survival and migration in mouse dermal fibroblasts in a short-term exposition. Our data demonstrated that olive oil and oleic acid promoted reactive oxygen species (ROS) production, while olive oil and hydroxytyrosol stimulated nuclear factor erythroid 2-related factor 2 (Nrf2) activation. Olive oil-mediated ROS production increased nuclear factor kappa B p65 expression, while olive oil-stimulated reactive nitrogen species production augmented the levels of Nrf2. Olive oil augmented cell proliferation, cell migration, and AKT phosphorylation, but decreased apoptotic cell number and cleaved caspase-3 levels. The effect of olive oil on cell migration and protein levels of AKT, BCL-2, and Nrf2 were reversed by an Nrf2 inhibitor. In conclusion, the activation of the Nrf2 pathway by olive oil promotes the survival and migration of dermal fibroblasts that are essential for the resolution of skin wound healing.

Shalaby K. Effect of Olive Oil Acidity on Skin Delivery of Diclofenac: In Vitro Evaluation and Ex Vivo Skin Permeability Studies. J Biomed Nanotechnol. 2022 Jan 1;18(1):234-242. doi: 10.1166/jbn.2022.3219. 

Abstract. Olive oil is a vegetable oil which has been successfully used as a skin penetrating agent. Acidity of olive oil is considered as one of the characteristic properties of olive oil. Olive oil acidity was selected as a parameter under investigation for evaluation of skin permeability. The acidities of the three investigated olive oils are varying from 0.75±0.16 to 2±0.17. Olive oil with acidity equals 2.0 showed the highest skin permeation for 12 h and cutaneous deposition with significant difference compared to the permeation values of 0.75 and F1.4 acidities. Results of cutaneous secretion of cytokines suggested that higher penetration was accompanied higher cytokines' secretions. Olive oil with acidity equals 2.0 also showed more prominent skin changes which suggested to be due to acidity and fatty acids' content. These results suggest that olive oil might improve the epidermal permeability, which is more pronounced in highly acidic olive oil, through weakening of skin barriers followed by acting of cytokines on re-building effective barriers. Finally, based on the current study, highly acidic olive oil is more efficient skin permeation enhancer vehicle than less acidic ones and can be efficiently used in formulation of cutaneous drug delivery systems.

Cooke A, Cork MJ, Victor S, Campbell M, Danby S, Chittock J, Lavender T. Olive Oil, Sunflower Oil or no Oil for Baby Dry Skin or Massage: A Pilot, Assessor-blinded, Randomized Controlled Trial (the Oil in Baby SkincaRE [OBSeRvE] Study). Acta Derm Venereol. 2016 Mar;96(3):323-30. doi: 10.2340/00015555-2279.

Abstract. Topical oils on baby skin may contribute to development of childhood atopic eczema. A pilot, assessor-blinded, randomized controlled trial assessed feasibility of a definitive trial investigating their impact in neonates. One-hundred and fifteen healthy, full-term neonates were randomly assigned to olive oil, sunflower oil or no oil, twice daily for 4 weeks, stratified by family history of atopic eczema. We measured spectral profile of lipid lamellae, trans-epidermal water loss (TEWL), stratum corneum hydration and pH and recorded clinical observations, at baseline, and 4 weeks post-birth. Recruitment was challenging (recruitment 11.1%; retention 80%), protocol adherence reasonable (79-100%). Both oil groups had significantly improved hydration but significantly less improvement in lipid lamellae structure compared to the no oil group. There were no significant differences in TEWL, pH or erythema/skin scores. The study was not powered for clinical significance, but until further research is conducted, caution should be exercised when recommending oils for neonatal skin.