The olive tree (Olea europaea) and its derivatives are a fundamental element of the Mediterranean diet.
Lipids present in the fruit and other components derived from olive byproducts have been widely used for their numerous health-promoting properties, such as anti-inflammatory, antimicrobial, and antioxidant activities.
The minor compounds of extra virgin olive oil represent 2% of its total weight and include more than two hundred and thirty compounds, in particular hydrocarbons, sterols, aliphatic alcohols, tocopherols, pigments, volatile compounds and phenolic compounds, mainly flavonoids, lignans, phenolic acids, phenolic alcohols and secoiridoids. Many of the health benefits of extra virgin olive oil are related to the significant antioxidant compounds. These properties have made them the center of attention as nutraceutical targets for the food and pharmaceutical industries, as they represent potential preventive agents for chronic and degenerative diseases and pathologies related to oxidative stress processes.
The olive leaf is a by-product that represents up to 10% of the weight of the tree and is an excellent source of bioactive compounds, such as oleuropein (OLE), verbascoside (VerB), rutin (RU), rutin (tyrosol (Tiro ) and hydroxytyrosol (Htyr), to which various biological properties such as immunomodulatory, anti-inflammatory, antioxidant and other activities have been attributed.
The oil extraction process generates two types of products, olive pomace (OP) and mill wastewater (OMW). Both are sources of phenolic compounds, sterols, pentacyclic triterpenes, carotenoids and mono- and polyunsaturated fatty acids 19 which give them anti-inflammatory, antioxidant, hepatoprotective, gastroprotective, anti-diabetic and lipid properties.
Numerous studies have underlined the protective effect of olive compounds on skin aging, thanks to their role in the different mechanisms involved in the aging process, such as the reduction of oxidative stress, the increase in cell viability and the decrease in histological alterations. Regarding their photoprotective effect, the olive tree and its fruit contain phenolic compounds that have a protective effect against radiation, such as low ultraviolet absorption and high antioxidant activity, acting as a protective factor against photocarcinogenesis. They also showed 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 demonstrated the ability to stimulate growth, migration and the expression of genes involved in cell differentiation, which promotes the regeneration of skin wounds.
Effects of olive oil and derivatives on skin aging
Numerous studies have pointed out the protective effect of olive compounds on skin aging, thanks to their role in the various mechanisms involved in the aging process. These compounds include squalene (Sq) from olives or their derivatives. In an in vitro test with HaCat keratinocytes, some authors observed a significant reduction in oxidative stress, an increase in cell viability and a reduction in histological alterations in a 3D human skin model, which could translate into a protective effect against the appearance of signs of aging. The same authors studied the antioxidant effect of Sq compared to a solution of Sq and C-60 fullerene in a clinical study, analyzing wrinkle formation and skin hydration. Both treatments reduced the area and depth of wrinkles, although not significantly, and increased skin hydration.
However, the anti-aging effect derived from the compounds present in the olive tree is not limited to its topical application, but benefits have also been reported from the consumption of extra virgin olive oil. The main reason is its fat composition, i.e. its composition in fatty acids. DNA is particularly sensitive to oxidative damage, and the oil may prevent the amplification of this damage in the skin.
Anti-inflammatory and antioxidant effects of olive oil and derivatives
Another effect attributed to the phenolic compounds of extra virgin olive oil is their anti-inflammatory activity, due to their antioxidant activity or the regulation of signaling molecules involved in inflammation, cell adhesion, cell growth, apoptosis and aging. In this sense, the effect of different oils on the antioxidant action was demonstrated in the NIH-3T3 cell line, demonstrating that the increase in phenolic compounds depending on the variety of extra virgin olive oil produces an increase in the antioxidant action, a due to the reduction of reactive oxygen species (ROS).
Photoprotective effects of extra virgin olive oil and olive derivatives
Solar light is the total spectrum of electromagnetic radiation coming from the Sun. It is composed of ultraviolet (UV) radiation of various types: UVC (from 100 to 280 nm), UVB (from 280 to 315 nm) and UVA (315 to 400 nm ) as well as visible light (400-700 nm) and infrared radiation (700 nm to 1 mm). The atmosphere is capable of completely absorbing UVC radiation and most UVB radiation. Therefore, the only solar UV radiation relevant to health is the UVA and UVB wavelengths.62 Exposure to radiation of these types is a very aggressive factor for human skin. In this sense, UV radiation generates chronic inflammation in the skin, which initially translates into an alteration of the outermost surface lipids, progressively reaching the vital layers of the epidermis and the underlying dermal compartments. Furthermore, UV rays induce the dilation of dermal blood vessels, vascular hyperpermeability, skin edema, hyperplasia, leukocyte infiltration, an increase in pro-inflammatory cytokines and the generation of ROS and other free radicals which end up producing direct damage to DNA, increasing the risk of undergoing mutations that can lead to different types of skin cancer.
The olive tree and its fruit contain some phenolic compounds that exert a protective effect against UV radiation, and are used as natural active ingredients in the formulation of sun filtersas they have structures and mechanisms of action similar to chemical UV filters, they synergistically improve their action and improve their resistance to water.
In this sense, OLE and Htyr, present in olive leaves, show low UV absorption and high antioxidant activity, acting as protective factors against photocarcinogenesis. Olive leaf extract has greater antioxidant power than OLE alone due to its synergistic effects with other phenolic compounds present in the leaf.
Compounds extracted from OMW also showed photoprotective and antioxidant effects on UVA-treated keratinocytes, and pro-oxidative and pro-apoptotic effects on genetically damaged keratinocytes.
On the other hand, both in vitro and in vivo studies have shown that Phenolic compounds found in olives can also protect against the effects of UVB rays.
Some studies also suggest that topical use of olive oil not only protects against the harmful effect of UV radiation, but may also be beneficial for cancer patients undergoing radiation therapy and radiochemotherapyin order to delay the appearance of skin lesions associated with irradiation and reduce their severity, thus improving their quality of life.
The antimicrobial effects of olive oil and olive derivatives
Bacterial infections are the cause of many skin problems. Some strains of Staphylococcus and Streptococcus are part of the saprophytic flora and can act as opportunistic infectious agents on certain occasions. In this regard, Streptococcus pyogenes, Staphylococcus aureus and Staphylococcus epidermidis are involved in the development of skin infections such as impetigo and pyoderma and infections of the nasal mucosa. Another common skin problem is bacterial colonization of wounds, caused by a lack of oxygen or a hypoxic state that hinders wound healing. Among all the microorganisms that are frequently isolated from chronic wounds are Escherichia coli, Candida albicans, Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Pseudomonas aeruginosa and Proteus spp.
Several studies have addressed the antimicrobial activity of olive leaf extracts against specific microorganisms such as Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. In this regard, several works have discovered that ethanolic extracts of olive leaves were effective in controlling the growth of these microorganisms, with minimum inhibitory concentration (MIC) values from 2.5 to 60 mg mL and minimum bactericidal concentration values ( MCB) 25 to 45 mg mL.
As for by-products, recent research has further investigated the antimicrobial activity of functional ingredients from different pomace varieties against Staphylococcus aureus, Escherichia coli and Candida albicansdemonstrating that these products with higher Htyr content also showed the best MIC against the tested bacteria, except Candida albicans.
Biostimulant and regenerative effects of olive oil and olive derivatives
The biological properties of the bioactive compounds of both leaves and extra virgin oil make them particularly interesting for use as biostimulants in the treatment of wounds.
Htyr, one of the main phenolic compounds of the oil, has a direct effect on the wound healing process, although the molecular mechanisms responsible for this activity have not yet been clarified.
The therapeutic potential of Olea europaea leaf extracts for skin regeneration was also studied, which showed antioxidant and protective effects against oxidative stress, showing a significant decrease in ROS and lipid peroxidation levels.
The effects of the extracts have also been studied on chronic wounds in humans. Regardless of their etiology, a greater number of patients achieved good results after the application of the extracts in hydrogel form, with a significant reduction of the wound area and an acceleration of the healing process compared to that of the control.
The benefits of olive oil and its derivatives are not only limited to treating chronic wounds, but have also been used to treat other skin conditions such as burns.
Conclusions
Various studies have shown that the olive tree and its derivatives have beneficial effects in the treatment of skin aging, solar radiation, oncogenic processes in the skin and protection against infections caused by microorganisms. Furthermore, some components of the olive tree have biostimulant, anti-inflammatory and regenerative effects at the tissue level. Therefore, the use of these compounds can be a good therapeutic option or alternative for the treatment of certain skin-related conditions and for the improvement and homeostatic maintenance of the skin.
