What is an oil macerate?

An oil macerate is the result of the maceration of parts of aromatic plants (flowers, leaves, roots, buds, young shoots, etc...) that has taken place in a neutral vegetable oil, which then acts as a carrier/solvent for the active properties of the plant. Indeed, the liposoluble active substances contained in the plant (essential fatty acids, vitamins, esters, alcohols, etc...) are transferred to the vegetable oil.

The term "macerate" can also refer to a extract obtained by macerating natural elements in a mixture of water, ethyl alcohol, and glycerin in order to extract the water-soluble active ingredients, such as tannins, phenols, certain vitamins, mineral salts, alkaloids, and most flavonoids: this is then referred to as a glycerin macerate.

What are the properties?

Depending on the plant and the part of the plant chosen, oil macerates can contain various actions, brought about by the different molecules that compose them, in addition to those of the carrier oil. Thus, they can be nourishing, softening, sebum-regulating, toning, healing... Moreover, it penetrates very quickly into the epidermis, which allows for the reconstitution of the skin's hydrolipidic film through a composition rich in essential fatty acids.

How to use it?

The oil macerate is applied at the end of the routine after the moisturizer, due to its oily texture. It can be used alone or in combination with others. A significant advantage of opting for oil macerates is that they can be a good alternative to essential oil, given that the latter has usage restrictions and therefore requires greater precautions, particularly in pregnant or breastfeeding women, and children. Indeed, an oil macerate provides the same benefits but with fewer harmful effects.

Why resort to maceration?

The "maceration" option is preferred when it is challenging to produce oil from the selected plant, even though it possesses intriguing properties. Indeed, the vegetable oil is a fatty substance extracted from an oilseed plant, meaning a plant whose seeds, nuts, or fruits contain fatty acids.

Be mindful of the terminology used. Some "oil macerates" may be referred to as "vegetable oil".

Maceration is an extraction technique that involves "infusing" a part of an aromatic plant in a neutral vegetable oil for a defined period, here are the steps:

1. Preparing the plant: An oil macerate is typically obtained from dried plants, particularly for parts rich in water such as bulbs, fruits, roots, etc. Indeed, this step prevents the water contained in the fresh plant from deteriorating the macerate due to the risk of fermentation. Of course, choosing between a dry or fresh plant also depends on the extraction process used. If the maceration is done hot, using a fresh plant is not a problem. In other cases, the plant is sometimes ground into powder before being left to macerate;

   Information : Certain plants may lose some of their properties if they are dried, such as lemon balm, St. John's wort, etc...

2. Selecting the maceration oil: Of the type olive oil, of sunflower, grape seed, argan, etc... the oil used should be selected based on its intrinsic properties, that is, its composition in fatty acids or unsaponifiables. It is recommended to choose a mono-unsaturated oil, with good stability at room temperature, and a low oxidation potential, thus ensuring long-term use of the macerate. Of plant origin, this carrier oil should preferably be obtained by first cold pressing for better preservation of thermolabile compounds (vitamins, antioxidants, etc...) and having undergone no treatment before or after pressing: it is then qualified as virgin oil;

3. There are two maceration processes with incubation times ranging from a few hours to several weeks, depending on the type of plant and the chosen extraction method:

• Hot Maceration: This technique involves heating the "oil + plant" mixture in an oven, in an inert atmosphere to prevent oxidation, in order to accelerate the release of active ingredients. The downside? Although it only requires a few hours of maceration, this method nevertheless carries the risk of altering certain active ingredients such as vitamins, flavonoids... which are sensitive to high temperatures;

• Cold Maceration: The absence of temperature elevation allows for the preservation of the integrity of thermolabile chemical species (vitamins, flavonoids...), and thus their properties. This process is done at room temperature or in the sun to utilize its heat (solar maceration); however, the mixture must be protected from UV rays that can promote the oxidation of the vegetable oil or alter the active components of the plant. The downside? This maceration process requires a longer impregnation duration of the plant extract by the fatty substance (between 3 and 4 weeks).

In the cosmetics industry, the oil macerate is obtained by simple pressing of plant extracts to extract the liposoluble active ingredients.

Sometimes, preservatives, such as Vitamin E (INCI name: Tocopherol), or even an essential oil like rosemary essential oil, are added at the end of the procedure to keep the mixture as long as possible.

Here are some examples of macerates, the most well-known and widely used in the cosmetics industry:

• The arnica macerate (INCI name: Arnica Montana Flower Extract) is recognized for its anti-inflammatory and healing virtues due to its content of sesquiterpene lactones (helenalin, arnifolin, etc...). It thus helps to alleviate various ailments (sunburn, superficial burns, shocks, insect bites, etc...). Its circulatory effect makes it an ideal ingredient to prevent blood accumulation and therefore reduce the formation of edemas or bruises. It also serves as a good base for massage oil, appreciated for relaxing muscles after a workout and preventing soreness or for treating a painful joint, or in prevention of intense muscular activity. This practice also helps to alleviate heavy legs. The oily arnica macerate also has antioxidant properties conferred by its content of omega-6 and 9 and polyphenols, thus protecting the skin from premature aging. Moreover, its high rate of carotenoids lends it a photoprotective role.

  Any contraindications? Do not use on open wounds.

• The calendula macerate (INCI name: Calendula Officinalis Flower Extract) is particularly suitable for individuals with sensitive, irritated skin prone to discomfort. It is primarily anti-inflammatory and antioxidant, with added soothing, nourishing, healing, and photoprotective properties. Indeed, its high content of faradiol esters allows it to act on all types of skin inflammation, in connection with its soothing action. Moreover, it also limits the appearance of signs of aging with its antioxidant virtues thanks to its high level of carotenoids (beta-carotene, flavoxanthin, lutein, lycopene, etc...) and flavonoids (quercetin, lupeol, etc...). Indeed, it fights against free radicals, responsible for cellular degeneration. In addition, thanks to the presence of flavonoids and faradiol, the calendula oil macerate helps to accelerate the regeneration of skin cells. Finally, due to its high oleic acid content, it also has nourishing properties, thus allowing it to hydrate the layers of the skin, and restore its suppleness and elasticity.

  Any contraindications? If you're allergic to Asteraceae, it's better to err on the side of caution and not use it.

• The carrot oil macerate (INCI name: Daucus Carota Sativa Root Extract) is known for providing a "healthy glow" effect, making it a friend to dull and tired skin. Thanks to the lutein and beta-carotenes (provitamin A), a coloring substance it contains, it imparts a slight natural "bronzed" tint to the skin, thus reviving dull complexions. Beta-carotene also has the ability to stimulate the synthesis of melanin. Its high content of antioxidant actives (beta-carotene, xanthine derivatives, lutein...) also allows it to protect the epidermis against daily aggressions, due to their antioxidant properties: it will capture the free radicals produced by sun exposure and thus fight against the effects of aging. In addition, it is appreciated by people with dry and curly hair due to its nourishing properties with its high content of linoleic and oleic acid. This also helps to strengthen the skin's hydrolipidic film, thereby preventing dehydration.

  Any contraindications? There are no contraindications to the cosmetic use of carrot macerate.

• The St. John's Wort macerate (INCI name: Hypericum Perforatum Oil) soothes, repairs, and heals damaged and stressed skin (burns, sunburns, dermatitis, diaper rash in babies...). Indeed, it aids in skin regeneration by stimulating collagen synthesis by fibroblasts, an action conferred by the phytosterols (hypericin, hyperforin) it contains. Its content of hypericin, hyperforin, and sesquiterpene terpenes also helps to limit the extent of inflammatory reactions. The St. John's Wort macerate also proves to be antibacterial due to the presence of hyperforin. Finally, this macerate is rich in omega-9 (oleic acid), contributing to maintaining skin hydration.

  Any contraindications?This oil macerate contains photosensitizing molecules (hypericin and its derivatives), meaning that exposure to the sun is strongly discouraged following its application, otherwise, you risk getting brown spots.

• DE WITTE P. A. & al. Skin photosensitization with topical hypericin in hairless mice. Journal of Photochemistry and Photobiology B: Biology (1999).

• MERFORT I & al. Skin penetration studies of Arnica preparations and of their sesquiterpene lactones. Planta Medica (2004).

• TASDEMIR D. & al. Assessment of antimicrobial and antiprotozoal activity of the olive oil macerate samples of Hypericum perforatum and their LC–DAD–MS analyses. Food Chemistry (2013).

• CASADO J. & al. Anthocyanin profile and antioxidant capacity of black carrots (Daucus carota L. ssp. sativus var. atrorubens Alef.) from Cuevas Bajas, Spain. Journal of Food Composition and Analysis  (2014).

• PAVLOV A. Plant Cell culture as emerging technology for production of active cosmetic ingredients. Engineering in Life Sciences (2018).

• SOUZA L. C. & al. Anti-inflammatory effect of Arnica montana in a UVB radiation-induced skin-burn model in mice. Cutaneous and Ocular Toxicology (2020).

• YU L. & al. Triacylglycerols and fatty acid compositions of cucumber, tomato, pumpkin, and carrot seed oils by ultra-performance convergence chromatography combined with quadrupole time-of-flight mass spectrometry. Foods (2020).