Bloglovin
Feedly
Twitter
Facebook
Showing posts with label Ingredient of the Week. Show all posts
The Ingredient of the Week is ascorbic acid, also known as Vitamin C.
 |
| L-ascorbic acid (Vitamin C) |
(For earlier discussions of Vitamin C, see here and here.)
Ascorbic acid occurs naturally in both plants and animals, but humans lack the ability to synthesize it so it must be obtained through our diet. Ascorbic acid is required for numerous biochemical pathways in the human body, including the biosynthesis of collagen, which is an important structural component of connective and epithelial tissue (which includes skin). A deficiency in Vitamin C gives rise to scurvy, a potentially fatal disease if not treated in time.
 |
| James Lind, a Scottish physician who carried out some of the first recorded clinical experiments, showing that citrus fruits could be used to treat and prevent scurvy. |
 |
| Oxidation of ascorbic acid; last step carried out in the presence of a metal ion, in this case silver (Ag+). |
One way to preserve the activity of Vitamin C is to combine it with other antioxidants, the idea being that the presence of other antioxidants will compete for reaction with free radicals. An example of such an antioxidant is Vitamin E (also known as tocopherol).
 |
| alpha-Tocopherol (Vitamin E) |
 |
| Cross section of epidermis |
Cellex-C High Potency Serum (see below for ingredient list) is the original Vitamin C serum, introduced in 1994. It is a straightforward formulation of 10% ascorbic acid in water, along with acetyl tyrosine (an amino acid), zinc sulfate, sodium hyaluronate, and bioflavanoids derived from green tea (Camellia sinensis). It is free of any extraneous ingredients: it is fragrance- and colorant-free, as well as being free of preservatives.
 |
| Cellex-C High Potency Serum (available in Toronto at The Anti-Aging Store) |
Dr. Lisa Kellett is a well-known dermatologist based in Toronto. Along with a cosmetic dermatology practice, she also has her own skin care line. Thanks to Helen Vong, editor-in-chief of TheSkiny.com, I got the chance to review Dr. Kellett's Topical Vitamin C Ferulic Serum (see below for ingredient list).
 |
| Kellett Topical Vitamin C Ferulic Serum (available in Toronto at DLK on Avenue; also available online HERE) |
The form of Vitamin C found in the Kellett serum is tetrahexyldecyl ascorbate, which is an oil-soluble derivative of ascorbic acid. As tetrahexyldecyl ascorbate is oil-soluble, it can penetrate the skin much more readily than ascorbic acid. According to the formulators of this serum, tetrahexyldecyl ascorbate penetrates the skin three times higher than ascorbic acid, when both are applied at the same concentration. The Kellett serum contains additional antioxidants, Vitamin E (tocopherol), green tea extract, and ethylhexyl ferulate (an oil-soluble form of ferulic acid, a plant-derived antioxidant). The combination of antioxidants acts to stabilize each other and thus increase their overall effectiveness, as well as increase the shelf-life and stability of the formulation.
Finally, the Kellett serum contains tridecyl salicylate, an oil-soluble derivative of salicylic acid, a chemical exfoliant which serves to further refine skin texture. It is free of fragrance, colorants, and preservatives.
The Kellett serum is comparable to SkinCeuticals C+E Ferulic Skin Serum (see earlier review here). Although the Kellett serum comes with instructions to apply every other night, I decided to follow the same regimen as with the SkinCeuticals serum, i.e. applying in the morning, followed by SPF 30 sunscreen over top, before heading out for the day, the idea being to use the antioxidants in the serum to protect skin against oxidative damage from environmental exposure during the course of the day. However, due to the presence of the salicylate, those with sensitive skin should stick with applying the serum at night, and be sure to wear sunscreen during the day.
Because this is a silicone solution, it is appears as a very thin, oily liquid that absorbs quickly with a very fast dry-down, so you have to spread very quickly before it absorbs. When I first started using this, I used about 5 drops, but found that after about a week of this regimen, I started to break out and I was getting a lot of plugged pores. From long experience, I know that silicone-based formulations don't work well on my oilier, stress-prone skin type, and so I was not surprised that I had this initial reaction to the Kellett serum. (Besides the breakouts, too much of it makes my skin feel uncomfortable and slightly itchy.) I cut back to 2-3 drops per application, working quickly to apply a very thin film, and that has worked out better for me - no breakouts and far fewer plugged pores. If you have a similar issue with silicone-based formulations, I think the key to this one is to apply very sparingly.
The Kellett serum definitely helps to boost radiance and to refine skin texture. Unlike the Cellex-C serum, the Kellett serum is colourless. More importantly, it does not appear to change colour over time, and it does not need to be refrigerated. The Kellett serum has almost no odour at all, a big plus compared to the SkinCeuticals serum, which had a strong, unpleasant odour of amines, similar to uncooked hotdogs. This serum is recommended for its ease of use, and its anti-ageing and skin-protective effects.
*In this review: Cellex-C High Potency Serum was purchased by me; Kellett Topical Vitamin C Ferulic Serum courtesy of TheSkiny.Com and DLK on Avenue. Thank you to Helen Vong, editor-in-chief of TheSkiny.Com for the opportunity to review the Kellett serum. This review is cross-posted to TheSkiny.Com, an e-magazine dedicated to the latest in beauty and dermatology - please check it out here!
***
IngredientsCellex-C High Potency Serum: water, ascorbic acid, acetyl tyrosine, zinc sulfate, sodium hyaluronate, bioflavanoids (from Camellia sinensis).
Kellett Topical Vitamin C Ferulic Serum: cyclomethicone, tetrahexyldecyl ascorbate, tridecyl salicylate, dimethiconol, hexyldecanol, bisabolol, cetyl cetyl hydroxyproline palmitate, stearic acid, rapeseed sterols, tocopherol, ethylhexyl ferulate, Camellia oleifera (green tea) extract.
This week's Ingredient is phenoxyethanol.
 |
| 2-phenoxy-1-ethanol |
As mentioned in last week's review of parabens,
it is becoming more and more popular to market products as being
"paraben-free". In such products, phenoxyethanol is commonly used as a
replacement for parabens in the formulation. Seeing as its popularity as
a preservative is only bound to rise in the face of all the negative
press regarding parabens, it is worth taking a closer look at
phenoxyethanol.
Phenoxyethanol acts as a bactericide, by inhibiting synthesis of nucleic
acids in bacteria, as well as acting on bacterial cell walls by causing
them to become more permeable to potassium ions (see Gilbert et al., Microbios. 1977;19(75):17-26; Microbios. 1977;19(76):125-41.).
It is effective against both gram-negative and gram-positive bacteria
as well as yeast. It is also used as an antiseptic, tissue preservative,
and organic solvent. It is naturally occurring in certain green teas.
Phenoxyethanol is present in concentrations of up to 5% in a skin care
formulation, typically in concentrations of around 1%; in Europe, it is
allowable in concentrations up to 1% with the provision that it may be
included in higher concentrations if it is to be used for other purposes
besides a preservative (see J. Am. Col. Toxicol. v. 9, no. 2, 1990; link)
The main selling point of phenoxyethanol is that is does not have the
weak estrogen-mimicking activity of the parabens. From the formulator's
point of view, although it is slightly more expensive than parabens, it
has similar formulation characteristics to the parabens, making it a
fairly straightforward replacement (I should mention here, the cost of
raw ingredients for creating skin care products is a major factor when
deciding what ingredients to include in a formulation).
It is accepted as a safe cosmetic preservative by government regulatory
agencies in the U.S., Europe and Japan. However, it has not been
entirely free of controversy. Like many other organic solvents,
phenoxyethanol is known to be a depressant of the central nervous system
and an irritant that may cause vomiting and diarrhea, if exposed at
high enough concentrations. In 2008, the FDA published a warning against
Mommy's Bliss Nipple Cream for use by nursing mothers, as it contained
both phenoxyethanol and chlorphenesin, another preservative known to
have harmful effects on the central nervous system (link: original FDA report).
Many children's toiletry products that are marketed as paraben-free
contain phenoxyethanol as the preservative. An example is the Treehouse
body lotion I reviewed earlier (see here).
 |
Treehouse Unscented Body Lotion by Nature Clean
(see review here)
|
When deciding what skin care products to buy for yourself or your
family, one has to balance risk versus benefit. As with the parabens,
the precautionary principle applies. In the case of children's products
like a nipple cream or a lip balm, something that is obviously going to
be ingested by a young child, then it is definitely not worth the risk of exposure. (As mentioned in my review of the Treehouse lotion here,
one has to be particularly vigilant about what chemicals children are
exposed to.) However, for most other products that are going to be
applied topically to either skin or hair, then the presence of
phenoxyethanol is probably not a significant concern since the amount of
phenoxyethanol absorbed through the skin is likely far too low to
trigger the symptoms noted above.
As always, I continue to look for safe alternatives and will report as I
find them. I have an extensive review coming soon on a series of
products that does not contain either parabens or phenoxyethanol -
please stay tuned!
This week's featured Ingredients are food-grade preservatives sometimes
used in cosmetics and beauty products: benzoic acid, sorbic acid,
levulinic acid, and their related salts.
Benzoic acid has a long history, having been discovered back in the sixteenth century. It is the chief component of benzoin gum, a resin derived from several species of trees in the genus Styrax. It is also found in many other plants, particularly plants with berry fruit (e.g. cranberries, bilberries). Its antimicrobial effect was first noticed in 1875, and it has been used as a food preservative since then.
Salts of benzoic acid, e.g. sodium benzoate and potassium benzoate, are
preferred as preservatives, as they are water soluble; they are commonly
used in processed foods and drinks. In a water-based solution, the salt
dissociates into the metal ion (sodium or potassium) and benzoate ion.
Benzoic acid and benzoate are effective as preservatives at acidic pH
levels.
There was some controversy in the 1990s when trace amounts of benzene were discovered in some soft drinks that had been stored for long periods of time. This is because under certain conditions, benzoic acid or benzoate ion can decarboxylate (i.e. lose its carboxylic acid group) to form carbon dioxide (CO2) and benzene, which is a known carcinogen. Two possible mechanisms for this decarboxylation reaction are shown below (Britt, P. F., et al. (1999, August). "Mechanistic investigations into the decarboxylation of aromatic carboxylic acids." In Conference: National American Chemical Society Meeting, New Orleans, Los Angeles.).
In addition to the above mechanism, the decarboxylation of benzoic acid in water solution can also be catalyzed by the presence of ascorbic acid (Vitamin C) and a transition metal such as copper (II) and iron (III) (Gardner, L. K., et al. (1993) "Benzene production from decarboxylation of benzoic acid in the presence of ascorbic acid and a transition-metal catalyst." Journal of Agricultural and Food Chemistry 41(5): 693-695; source). Benzoic acid itself is believed to be relatively non-toxic. Benzene formation is believed to only be a concern if the preparation is stored for long periods of time and at appropriate reaction conditions that would allow it to form.
Like benzoic acid, sorbic acid was also first discovered as a component of a plant. In this case, sorbic acid was discovered in the berries of the rowan tree, Sorbus aucuparia, in 1859. The antimicrobial effect of sorbic acid was discovered in the late 1930s. Salts of sorbic acid are the preferred form, as they are water soluble. Potassium sorbate is a commonly used salt of sorbic acid.
Levulinic acid is yet another compound first derived from a plant, and later discovered to have an antimicrobial effect. Levulinic acid was first isolated from corn. As with benzoic acid and sorbic acid, you will see the salts of levulinic acid more commonly used in cosmetic formulations.
Compared to parabens and phenoxyethanol, the food-grade preservatives
including benzoic acid, sorbic acid and levulinic acid, are not as
effective at inhibiting microbial growth. Typically you will see these
preservatives in processed foods that have a limited shelf life or else
they have special storage considerations, such as refrigeration or
packaging with an air-tight seal. When used in cosmetics, the shelf life
of the formulation is somewhat shorter compared to comparable
formulations containing parabens or phenoxyethanol. Also, their
antimicrobial activity is limited to formulations that are acidic (pH
< 7), which limits the type of formulation they may be used in. In
order to boost their efficacy, different food-grade preservatives are
often combined to inhibit a broader range of microbes.
The Diane Lai body lotions contain sodium benzoate and potassium sorbate, but note that these lotions are also packaged in an air-excluding pump, which helps to protect the formulation.
One of the original green/eco brands, Neal's Yard Remedies products
incorporate levulinic acid or sodium levulinate, the sodium salt of
levulinic acid.
By now, I hope you will have seen a theme here: all of the preservatives I have reviewed thus far, including parabens and phenoxyethanol,
are naturally occurring in various plants. All of these compounds serve
the same purpose in plants as they do in cosmetic formulations: to
protect from microbial growth, particularly fungal growth. For this
reason, antimicrobial agents are often found in flowers and fruits,
which are particularly prone to microbial attack, as they are loaded
with sugars and nutrients. From an evolutionary standpoint, it makes
sense for plants to protect these parts from microbes, as it is
important for the plant to preserve the freshness of its flowers for
pollinators and its fruits for passing birds and animals to consume (and
then carry its seeds to other locations). It just so happens that
parabens are very weakly estrogenic, while phenoxyethanol has negative
side effects if consumed in high enough quantities: this again
underlines the fact that just because something is natural does not mean
it is automatically good for you! The food-grade preservatives appear
to carry the least amount of risk but they are also not as effective as
preservatives in cosmetic formulations. As stated before, it's up to the
consumer to decide how much risk they are willing to take on when
deciding on a beauty product.
On a personal note: apologies for my absence last week. Things got really crazy over the past two weeks and I am just catching my breath now. Doing my best to get back on track now! I am still working on my major review of a new brand, which I hope to complete soon.
In other news, Google Reader was retired on July 1. If you were using Google Reader and you don't have a Blogger account, you can continue to follow via Feedly as well as Bloglovin, Facebook and Twitter (for these last three, please click the appropriate media follow button over to the right).
 |
| Soya sauce contains sodium benzoate. |
These preservatives are growing in popularity, particularly in the
green/eco segment of the beauty market, mainly due to the negative press
surrounding parabens, and to a lesser extent, phenoxyethanol (see
earlier reviews of parabens here and phenoxyethanol here), and the belief that food-grade preservatives are safer to use. Let's take a closer look at them!Benzoic acid has a long history, having been discovered back in the sixteenth century. It is the chief component of benzoin gum, a resin derived from several species of trees in the genus Styrax. It is also found in many other plants, particularly plants with berry fruit (e.g. cranberries, bilberries). Its antimicrobial effect was first noticed in 1875, and it has been used as a food preservative since then.
 |
| Harvesting resin from a Styrax benzoin tree; the dried resin is sold as benzoin gum. |
 |
Benzoic acid
|
There was some controversy in the 1990s when trace amounts of benzene were discovered in some soft drinks that had been stored for long periods of time. This is because under certain conditions, benzoic acid or benzoate ion can decarboxylate (i.e. lose its carboxylic acid group) to form carbon dioxide (CO2) and benzene, which is a known carcinogen. Two possible mechanisms for this decarboxylation reaction are shown below (Britt, P. F., et al. (1999, August). "Mechanistic investigations into the decarboxylation of aromatic carboxylic acids." In Conference: National American Chemical Society Meeting, New Orleans, Los Angeles.).
 |
| Proposed reaction mechanisms for decarboxylation of benzoic acid under acidic conditions, such as commonly found in food and drinks. Benzene is the simple 6-member aromatic ring shown as the final compound in each reaction pathway (1) and (2). (Source) |
In addition to the above mechanism, the decarboxylation of benzoic acid in water solution can also be catalyzed by the presence of ascorbic acid (Vitamin C) and a transition metal such as copper (II) and iron (III) (Gardner, L. K., et al. (1993) "Benzene production from decarboxylation of benzoic acid in the presence of ascorbic acid and a transition-metal catalyst." Journal of Agricultural and Food Chemistry 41(5): 693-695; source). Benzoic acid itself is believed to be relatively non-toxic. Benzene formation is believed to only be a concern if the preparation is stored for long periods of time and at appropriate reaction conditions that would allow it to form.
Like benzoic acid, sorbic acid was also first discovered as a component of a plant. In this case, sorbic acid was discovered in the berries of the rowan tree, Sorbus aucuparia, in 1859. The antimicrobial effect of sorbic acid was discovered in the late 1930s. Salts of sorbic acid are the preferred form, as they are water soluble. Potassium sorbate is a commonly used salt of sorbic acid.
 |
| Berries of the rowan tree; sorbic acid is naturally occurring in these berries. |
 |
Sorbic acid
|
Levulinic acid is yet another compound first derived from a plant, and later discovered to have an antimicrobial effect. Levulinic acid was first isolated from corn. As with benzoic acid and sorbic acid, you will see the salts of levulinic acid more commonly used in cosmetic formulations.
 |
| Corn (Zea mays). Commercially available levulinic acid continues to be sourced from corn as it is so abundant. |
 |
Levulinic acid
|
The Diane Lai body lotions contain sodium benzoate and potassium sorbate, but note that these lotions are also packaged in an air-excluding pump, which helps to protect the formulation.
 |
| Diane Lai Rejuvenate and Soothe lotions, along with the lip balms; link to review here. |
 |
| Neal's Yard Remedies Baby Bath & Shampoo contains levulinic acid. (reviewed earlier here) |
***
On a personal note: apologies for my absence last week. Things got really crazy over the past two weeks and I am just catching my breath now. Doing my best to get back on track now! I am still working on my major review of a new brand, which I hope to complete soon.
In other news, Google Reader was retired on July 1. If you were using Google Reader and you don't have a Blogger account, you can continue to follow via Feedly as well as Bloglovin, Facebook and Twitter (for these last three, please click the appropriate media follow button over to the right).