Rosemary extract is supposed to offer toning, astringency, increased blood circulation, as well as anti-oxidant, anti-inflammatory, analgesic, and anti-microbial features. It inhibits oxidative cell damage, and it can be added to our products to increase the shelf life. Finally, there is some suggestion rosemary extract might be anti-aging by offering a decrease in the appearance of fine lines and wrinkles.
There are six main components of rosemary oil that offer the awesome qualities we'll soon want in every product! They are carnosic acid, carnosol, ursolic acid, rosmarinic acid, rosmaridiphenol, rosmanol. Rosemary also contains chlorogenic acid, caffeic acid, and tannins.
Found in high levels in rosemary and sage, the carnosic acid is considered the main compound responsible for the high anti-oxidant levels of rosemary extract. It scavenges free radicals and hydrogen peroxide as well as hypochlorous acid (HOCl), a compound produced in our bodies at sites of inflammation. It also helps protect skin against UVA light, but I wouldn't use it as a sunscreen without testing!
When formulating with ingredients containing carnosic acid, we must add them in the cool down phase of our products as it is heat sensitive. It is also not great in aqueous solutions if said solution contains transitional metal ions. In other words, use distilled water. If you use tap water with some metal ions in it, it can send the carnosic acid into oxidation, which kinda defeats the purpose of using the ingredient in the first place. Or you can add some chelating ingredients (like EDTA or citric acid) to bind the metal ions. It converts to carnosol or rosmanol after free radical attack.
Carnosol is a diterpene found in rosemary that offers anti-oxidizing power more potent than BHT or BHA. It behaves as a free radical scavenger in our products. In rosemary extract, carnosol is slightly less effective than carnosoic acid as an anti-oxidant, but not by much (if carnosol is 1, then carnosoic acid rates a 1.2). It also has the ability to chelate iron in our products.
A pentacyclic triterpene acid, ursolic acid is also found in apples, basil, bilberries, cranberries, elder flower, peppermint, lavender, oregano, thyme, and prunes. It offers anti-inflammatory, anti-microbial, and anti-oxidant properties to our creations. It may have some effect on blood circulation at the skin level, stimulating blood flow. It is called an anti-aging polyphenol because it may help restore skin's collagen bundles and elasticity. And it is showing promise as an anti-fungal ingredient. It is a more effective anti-oxidant than BHT.
Ursolic acid is alleged to be good for hair growth and prevention of scalp irritation, which is why you'll see rosemary included in many hair care products. The claim is that hair growth is encouraged by "stimulating peripheral blood flow in the scalp and activating hair mother cells". It is recommended for dandruff prone hair for the same reason. Again, more studies must be done, meaning this isn't a confirmed feature of ursolic acid.
Ursolic acid works in an interesting way - it actually forms an oil resistant barrier (I've seen it called a "waxy coating") on our skin, so we get a little occlusion from it, keeping the good stuff in and the damaging outside world outside! It is being tested as a burn and wound healer, due to the awesome nature of the anti-inflammatory action, and as a possible treatment for Candida albicans (yeast).
A very active anti-oxidant, it works about as well as or better than BHT or BHA in lard (there are conflicting results about which one it is better than, but suffice it to say it is a good anti-oxidant). It is oil soluble, so it is more effective in products containing some oils than products that are completely water based.
So can rosemary do what is promises? Pretty much the answer is yes! It can behave as a very good anti-oxidant, it can help reduce sebum production for particularly oily people, it can increase blood circulation in our skin, it can behave as an anti-microbial and anti-viral ingredient, it can offer mild analgesic properties, and it is an anti-inflammatory. Is it anti-aging? In the sense that it can help protect against UV damage, free radical damage, increase circulation - which could lead to improved skin tone - and it may help restore collagen and skin elasticity. Does it work as an insect (flea and tick) repellant? I wasn't able to find confirmed proof of this, but I guess it can't hurt to use it that way if it's also offering the wonderful qualities for your skin (although some of us need heavy duty, toxic to most mammals kind of spray to keep away the fleas and ticks - I am like sugar to them!).
Join me tomorrow for more fun formulating with rosemary extract!