Traditionally, CO2 extracts are used in the manufacture of cosmetic products in their native, i.e., lipophilic (fat-soluble) form. With the appearance in our range of commercially produced water-soluble emulsions of CO2 extracts (CO2 microemulsions), however, many cosmetic companies also began to take a closer look at this product – initially with the aim of using this ingredient for its intended purpose, in aqueous media. That is, in products such as lotions and tonics.
But since the potential application range of CO2 microemulsions is much broader than that of purely aqueous media; they can also successfully replace conventional CO2 extracts in most conventional cosmetic products (such as creams, gels, ointments) in practice. We have therefore decided to create a brief overview article for our customers that explains the most important details of this issue.
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There is a significant difference between emulsions, mainly cosmetic, and microemulsions. This difference is due to the size of the lamellae or micelles. In conventional emulsions, these formations are quite large and cannot cross the barrier of the dermis; while the kernels of microemulsions are so small that they can easily penetrate the surface layer of the dermis and reach its deep layers. In addition, high molecular weight compounds such as paraffins are often used in cosmetic emulsions, which contribute to the occurrence of an occlusive bandage effect, which makes the emulsion more stable; At the same time, however, they also prevent biologically active substances from penetrating the dermis and can sometimes negate the expected effect.
CO2 microemulsions are oil-in-water emulsions, but their lipophilic phase consists of 100% concentrated CO2 extracts. When using CO2 microemulsions in cosmetic preparations, the greatest biological effect can be achieved by using agents with a minimum of high molecular weight thickeners (paraffins). These can be products such as cosmetic milk, alcohol-free toners or liquid emulsion products with a high content of water and dihydric alcohols. Such agents do not create additional barriers on the surface of the skin, and the size of the cores of CO2 microemulsions, which contain high concentrations of biologically active compounds, allows them to fully develop their beneficial properties. At the same time, CO2 microemulsions do not disintegrate in “light” cosmetic emulsions, i.e., their lipophilic micronuclei are completely retained and can fully develop their biological activity.
In “heavier” cosmetic emulsions, CO2 microemulsions break down and show up as a regular CO2 extract in the end product, but there is one important nuance. In practice, the most popular form of using CO2 extracts among cosmetics manufacturers is oil solutions of various concentrations, usually 10% solutions (A10). This situation has arisen for both economic and purely technical reasons – dosing highly concentrated 100% CO2 extracts (A100) for small batches is not very practical, so dilute oil solutions with a reduced concentration are often the best choice.
However, the dilution of the CO2 extract with oil has its own price, which is expressed in a certain decrease in biological activity due to the coating of the biologically active molecules contained in the extract with biologically inert molecules from the composition of fatty oils. Such a coating prevents complete contact of the extract with the skin and also makes it difficult to penetrate the deep layers of the dermis. At the same time, CO2 microemulsions do not have the disadvantages described above and are at the same time a solution of CO2 extract of low concentration, but not of oil, but of water. This means that the dosing of CO2 microemulsions is also more convenient than that of oil solutions, but at the same time their use does not result in any “pollution” in the form of fatty oils that get into the end product.
Taking into account the nuances described above, CO2 microemulsions can be recommended as a substitute for low concentration oil solutions, even if there are no more microemulsions in the end product, they will disintegrate and turn into a regular CO2 extract. Because in this case 100% of the extract gets into the product, without impurities in the form of fatty oils.
In cases where CO2 microemulsions remain in the end product as microemulsions (these are aqueous cosmetic products and “light” cosmetic emulsions), their use in products of this type is all the more justified for two reasons:
1) At the same injection rate with the oil solution, the biological activity of the product based on the CO2 microemulsion is higher due to the more efficient penetration of micronuclei into the deep layers of the dermis.
2) With the same biological activity, products based on CO2 microemulsions require lower ingredient addition rates and are more cost-effective than products based on oil solutions of CO2 extracts.
Let’s summarize what has been said. In conventional cosmetic preparations, most of the biologically active substances are bound in large, inaccessible structures, which means that their properties cannot fully develop and are partially lost. When using microemulsions, the effectiveness of the action of biologically active compounds increases significantly due to their ability to quickly penetrate the dermis. This effect makes it possible to reduce the entry rates of biologically active additives in the form of a CO2 microemulsion compared, for example, to oil solutions made from 100% CO2 extracts, and at the same time to achieve pronounced positive effects. At the same time, its use is justified in cases in which the CO2 microemulsion disintegrates in the end product, since its decomposition results in a “pure” CO2 extract without impurities in the form of oils.
Separately, it should be mentioned that the ability of CO2 microemulsions to easily form pseudo-solutions in water, which in most cases are optically transparent, enables technologists to create new types of cosmetic and cosmeceutical preparations with unique organoleptic properties and high biological activity. Such products (for example, in the form of tonics or lotions) have a higher biological activity compared to conventional creams, the ability to be easily absorbed, penetrate deep into the skin and at the same time leave no signs of use.