Leatha Questions Chirality:
I have started using a skin care line called Cosmedix and they claim that their products are chirally correct. I don`t know what this means and whether it is a marketing gimmick or if there is some truth to it.
The Left Brain Criticizes Cosmedix:
The term chiral is derived from the Greek work for handedness and a molecule is called chiral if it differs from its mirror image. (A simple way to visualize this concept is to think of your right and left hand. You can`t fit your left hand in your right glove, right? That`s because they`re chiral. You can learn more about the idea here.)
Some chemical reactions produce both the left handed and right handed version of the same molecule. These versions are called isomers. This concept is very important in drug manufacture where the Left and Right isomers may have different chemical properties. If the Left isomer is effective against a given disease, you want a chemical reaction that produces pure Left, not a mixture of Right and Left. So for drugs, chiral purity is very important.
But for cosmetic products, chirality isn`t really an issue. That’s because cosmetic ingredients don`t interact with the biological systems of your body the same way drugs do. So your first guess was correct “ this IS a marketing gimmick! Thanks for sending us your beauty questions.
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{ 4 comments… read them below or add one }
When I read the question, my first reaction was, WHAT!?!? CHIRALLY CORRECT? -Sigh, the gimmicks cosmetics companies use!!
Well, maybe you can look at it as cosmetic companies trying to inject scientific knowledge into society. Sure, they get it mostly wrong but maybe it will make someone look up what it really means and they’ll learn something.
Actually, the idea that isomers are irrelevant in dermatology is completely false. Skin is an organ system with complex chemistry and there is absolutely no reason that it would not be susceptible to the same chemical reactions, harmful or beneficial, as any other organ or organ system. The isomers of ascorbic acid are known to have vastly different effects on the skin. L-ascorbic acid is a potent antioxidant and it also stimulates production of collagen, so it is an ideal ingredient in fighting photoaging. D-ascorbic acid, however, produces free radicals and causes skin dryness and irritation. So a “chirally correct” product containing, for example, only stable l-ascorbic acid and no d-ascorbic acid would be much more effective than a product containing both isomers. Depending on the molecule and the activity of its isomers, having a “chirally correct” product can either be an oddly specific marketing gimmick, or a genuinely beneficial attribute.
@Rachel – thanks for your comments. Can you point us to any scientific literature or published studies that support the claim that topically applied D-ascorbic acid behaves any different than L-ascorbic acid? We are not aware of any published reports.