Starting this week and into next week, I am launching (hopefully!) regular weekly series. On Wednesdays, I will be featuring the Ingredient of the Week in which I will discuss a chemical compound, why it is found in cosmetic formulations, and products to watch out for that contain the ingredient in question. I will be delving a little further into the science - please take a look at the Chemistry 101 page (linked here and above) to get a handle on basic terminology.
Today, I am featuring hyaluronic acid. Hyaluronic acid (also known as hyaluronan; see below) is a polymer and a type of organic compound known as a glycosoaminoglycan. A glycosaminoglycan is an unbranched polysaccharide composed of repeating disaccharide units, in this case glucuronic acid and N-acetylglucosamine. The molecular weight of hyaluronic acid found in vivo is variable and dependent on the length of the molecule, ranging from 5,000 to 20,000,000 Daltons. (To give perspective, one molecule of water is ~18 Daltons.)
The repeating disaccharide unit of hyaluronic acid is shown above - you can see the skeleton of each saccharide unit as a 6-member ring, wherein the glucuronic acid group is on the left, and the N-acetyl glucosamine group appears on the right. The term "acid" refers to the presence of the carboxylic acid group (-CO2H) which is attached to the glucuronic group on the left. This carboxylic acid group can exist as a negatively charged carboxylate group (-CO2), which is also referred to as an anion. Thus, hyaluronan is the polyanionic form of hyaluronic acid, and it is the form that is typically found in vivo.
Hyaluronic acid is a naturally occurring structural molecule in humans, distributed throughout the connective, neural and epithelial tissues, including skin. It is one of the chief components of the extra-cellular matrix of these tissues, as well as being a major component of cartilage and synovial fluid (the lubricating fluid in synovial joints like the knee). As a component of the extracellular matrix, it serves as a means of facilitating cell surface receptor interactions, and as a lubricant, facilitating cell movement.
Many of these important functions are due to the fact that hyaluronic acid is a powerful humectant, a molecule that attracts and holds water. It is estimated that hyaluronic acid can hold up at 1000 times its own weight in water. In skin tissue, this ability to hold water is very important. Hyaluronic acid is necessary for maintaining the structural integrity of the extracellular matrix of dermal tissue (the layer of skin tissue below the epidermis, which is the outermost layer). It is also necessary for maintaining skin hydration and the barrier function of the skin, helping to slow down trans-epidermal water loss to the environment. It is also an important factor in skin tissue repair.
In cosmetic formulations, low molecular weight hyaluronic acid (< 5000 Da) or its salts (e.g. sodium hyaluronate) are added as a humectant, and to aid tissue repair and improve skin hydration. Given that it is a natural component of body tissue, it is highly biocompatible and skin sensitivity issues are very rare. Hyaluronic acid was formerly sourced from animal byproducts (like rooster combs!), but nowadays, it is usually produced by microbial fermentation of certain plants. As it is a fairly costly ingredient, effective concentrations of hyaluronic acid are typically only seen in higher end skin care products. Examples include Tata Harper's Rebuilding and Regenerating Moisturizer and Cellex-C Hydra-5 B-Complex (reviewed earlier here), both of which contain sodium hyaluronate.
|Tata Harper Rebuilding Moisturizer|
for oily/combination skin;
available at Jacob & Sebastian
Tata Harper Rebuilding Moisturizer is a lightweight but dense lotion that I have found to be really good for oily/combination skin types. It provides just the right amount of moisturizing without being overly rich and pore-clogging, a common problem I have found with green/eco-brand facial moisturizers. All of the ingredients are naturally derived, and it is free of all synthetic fragrances, preservatives and colourants; however, it does contain quite a few plant extracts and essential oils so those with very sensitive skin should patch test it beforehand.
The Cellex-C Hydra-5 B-Complex serum is basically an aqueous solution of sodium hyaluronate and Vitamin B-5. Although it appears to be pricey, it is actually an excellent value. I have found that a single drop is enough for the entire face, and after 3 months use, I still have half a bottle left. After applying, my skin feels really soft and well-hydrated. In the winter months, I layered it underneath a tiny pea-sized amount of Tata Harper Rebuilding Moisturizer and it was an excellent combination for guarding against dehydrated skin. Now that we are moving into summer, I have found that the Cellex-C serum on its own is fine for my combination/slightly oily skin type, and I just layer my sunscreen lotion directly over top.
|Cellex-C Hydra 5 B-Complex,|
available at The Anti-Ageing Store (with mail order across Canada)
Questions? Comments? Let me know!
In case you don't follow me on Facebook or Twitter, I have also launched Topical Tuesdays this week. Each Tuesday, I will try to post links to articles I have written that address commonly asked questions. Yesterday, I posted a link in response to the one question which nearly everyone - sooner or later! - has to deal with: how to zap that zit FAST! One way to do it is to use intense blue light. It is not a gimmick, there is scientific research to back it up and I can attest to its efficacy. I have tried both the professional medi-spa version as well as an over-the-counter device from Tanda. You can read all about it in this post HERE. Please follow me on Facebook and Twitter to keep up with future Topical Tuesday posts! :-)