Alpha hydroxy acids’ role in plant-based cosmetics

A naturalizing industry

In recent years the demand for the use of plant-based constituents in cosmetic formulations has grown significantly. The increased public awareness about the widespread use of synthetically produced chemicals has caused the cosmetic industry to move towards a more biological approach. In 2020, the global natural and organic cosmetics market was worth around 11.9 bn USD according to UK-headquartered research and experiencing a 2.9% increase compared to the previous year. But, given the economic importance of the natural cosmetic market, what are the exact requirements that a cosmetic has to meet in order to be a truly natural cosmetic?

Defining natural cosmetics

The most agreed-upon definition states that for a cosmetic product to be considered as natural it must be produced using plant or other natural extracts or ingredients and avoid synthetically produced chemicals; such as those which originate from petrochemical industries. As a result, many natural cosmetic products currently incorporate an ample amount of natural constituents as active ingredients in their formulations. The active constituents of cosmetics are widely referred to as ‘cosmeceuticals’. In natural cosmetics these compounds can be classified into five different categories, depending on their chemical structure and the specific activity they perform. These categories are:

• Vitamins;
• Antioxidants;
• Plant and marine extracts;
• Hydroxy acids; and
• Peptides and biologicals.

Given the complexity and diversity of possible chemical interactions between specific cosmeceuticals and the different cell types and cellular components of human skin, many compounds can be classified in more than one category.

The enormous potential of hydroxy acids

One particularly interesting group of active components of natural cosmetics is the so-called ‘hydroxy acids’. Hydroxy acids are small organic chemical compounds that share some similarities with one another in terms of their molecular structure. Hydroxy acids are frequently categorized into many additional categories, the most notable and well-studied of which are the ‘alpha hydroxy acids’, abbreviated as AHAs. Because they are organic acids, AHAs are safe to use on the skin in small amounts without causing irritation, yet their strong acidity and special structure allow for certain unique cosmetic uses. As a result, AHAs are currently being used in a plethora of skincare formulations as liquid exfoliants, to target acne and design to mitigate the visible signs of aging.

Effect of AHAs on the skin

Back in 1974, scientists discovered that AHAs could have a profound effect on ‘keratinization’ which meant they could show huge potential in cosmetics. Keratinization is the process in which keratinocytes, a type of skin cells, differentiate into corneocytes, the main constituents of the most outer layer of the skin. AHAs reduce the cellular cohesion between corneocytes thus inducing the cell shedding.

As such AHAs currently constitute a very popular dermatological tool in the treatment of acne, scars, hyperpigmentation, roughness, and age spots in the skin with minimal risk, and much safer than other physical or chemical alternatives. Additionally, AHAs act as humectants on the skin. Humectants are molecules that are able to penetrate into the skin and draw water from inner layers, thus hydrating it. AHA application results in an increase of water holding capacity of the skin, an increase in skin turgor as well as reduction in skin wrinkling. Furthermore, the acidity of these compounds also helps to preserve the cosmetic formulations they form a part of!

Plant sources of AHAs

But what would you think if I told you that AHAs are actually present in many plant species? Some examples of AHAs include glycolic acid, malic acid, tartaric acid, mandelic acid, and citric acid. One of the most used AHAs, glycolic acid can be found in sugarcane (Saccharum officinarum), whereas others like malic acid, tartaric acid, mandelic acid, and citric acid can be found in apples (Malus domestica), grapes (Vitis vinifera), almonds (Prunus dulcis) and lemons (Citrus x limon).

In 2016, researchers reported that AHAs could be separated in complex mixtures from fruits using already available biotechnological techniques. This process could help isolate these compounds of interest from their natural sources for later use in cosmetic formulations. Currently, a larger percentage of AHAs used in dermatologic and cosmetic products are produced through biotechnological means using certain bacterial species in industrial bioreactors. However, the market for cosmetic and dermatologic products containing AHAs derived from plants is booming. In the coming years, the majority of the cosmetic products we use will contain AHAs derived from our favorite plants such as apples, grapes, and so on.

All things considered, AHAs constitute one of the most versatile groups of naturally originated compounds present in cosmetic and dermatological formulations for a wide variety of applications.

For more interesting articles on different plant-based constituents used in the cosmetic industry, keep checking this space.

By David Alzuria Rodríguez | 8 August 2022

David Alzuria Rodrguez is a Spaniard from Barcelona. He holds a master's degree in plant biotechnology. He recently began performing plant science communication for Lab Associates in the form of short articles about plant-based cosmetics and pharmaceuticals. He has always been fascinated by nature and how it interacts with human societies. As a result, he decided to create an Instagram page, @plant_chem, dedicated to plant secondary metabolites as well as their properties and applications. He enjoys spending his spare time with friends and family, gardening, and hiking in the mountains.

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