𝗖𝗮𝗻 𝘁𝗵𝗲 𝗰𝘂𝗿𝗿𝗲𝗻𝘁 𝘁𝗿𝗲𝗻𝗱 𝗯𝗲 𝗰𝗼𝗻𝘀𝗶𝗱𝗲𝗿𝗲𝗱 𝗮 𝘃𝗮𝗹𝗶𝗱 𝗱𝗲𝗺𝗼𝗻𝘀𝘁𝗿𝗮𝘁𝗶𝗼𝗻 𝗼𝗳 𝘁𝗵𝗲 𝗲𝗳𝗳𝗲𝗰𝘁𝗶𝘃𝗲𝗻𝗲𝘀𝘀 𝗼𝗳 𝗮𝗻 𝗶𝗻𝗴𝗿𝗲𝗱𝗶𝗲𝗻𝘁 𝗳𝗼𝗿 𝗮𝗻𝘁𝗶𝗼𝘅𝗶𝗱𝗮𝗻𝘁 𝗯𝗲𝗻𝗲𝗳𝗶𝘁𝘀?
We decided to perform this experiment alongside offering an explanation as to why this cannot be considered a valid way to demonstrate the efficacy and antioxidant action of a skincare Vitamin C product and why we have decided to strongly question any use of it as a sound scientific experiment.
This is being used widely across social media and for marketing purposes, but does not take into account the significant differences between human and plant biology, the histological variances between fruit and human skin. Neither does it importantly take into account the many different forms of Vitamin C and the pH of the end product required in order for that ingredient to remain stable.
There could perhaps be other tests that using an apple could be valid for in terms in skincare, such as lightening ingredients, but they would need to take into even further consideration the differences between a fruit and human skin composition and how the various forms of Vitamin C ingredients are structured.
We carried out a very basic trial with slices of apple put into dishes and applied ascorbic acid, in some of the various forms that we use within Dermogenera as a brand but also included the less stable form, L-ascorbic acid.
The slices were left at room temperature and measured visible changes were measured at 6 hr and 12 hr interval.
It demonstrated clearly how each piece reacted differently to the application of ingredient over a period of time and we will now explain the reasons as to why that might be, despite many of the forms used, being proven to offer highly effective antioxidant properties on skin.
Whilst we not use base form L-ascorbic as an ingredient within our formulations, we wished to include it within our trial. We created a buffered dilution at 3% of each ingredient using in the hydrosoluble forms water & propylene glycol as solvents and in the case of the liposoluble form, caprylic capric triglycerides.
We used base ingredient form rather than specific formulated products containing them. This was to avoid any additional ingredients that may also affect the outcome of a test for enzymatic browning.
Firstly, its important to consider that human skin structure and function is very different to that of an apple, the permeation of any ingredient within human skin is much more complex and difficult to achieve than the flesh of an apple and also we must consider the molecular weight and delivery system of an ingredient, a molecular weight of over a certain size is unable to penetrate human skin beyond the surface, so then we must consider the presence of penetration enhancers which can also make one form of Vitamin C more effective than another in terms of skincare, a thing impossible to determine when applied to an apple instead of human skin where you have a different composition including the very significant presence of lipids in the latter.
Then to consider the focus of this trend, the browning of, or oxidation of an apple which is caused by the enzyme polyphenol oxidase, a pH related enzymatic reaction rather than free oxygen, this browning reaction can be prevented with not only the antioxidant ascorbic acid, but with any acid, so any acid ingredient would have had the same result. This occurs with fruit and is why when making a fruit salad you add lemon or orange juice to slow down this effect and prevent an unappealing discolouration.
The prevention of the browning is not necessarily an indication of effective antioxidant activity. Therefore if considering purely for this purpose the experiment doesn't really say that much about real antioxidant benefits, it says only that it can prevent an enzymatic process not relevant to protecting human skin where a different oxidative stress test would be more relevant.
It also does not take into consideration the highly effective antioxidant ability of any liposoluble ingredient such as Ascorbyl Tetraisopalmitate, as the apple tissue is water based so therefore a water based ingredient would penetrate where the potency of serum for skincare will depend on how the human skin processes it and skin being composed entirely differently to the flesh of an apple.
It is important also to consider in brief the different forms of ascorbic acid we selected for this trial and that are also widely used in skincare. Their structure, how they are created to enhance penetration, for stability, compatibility with other ingredients, long term performance within a formulation. In simplified terms each is ascorbic acid, restructured or engineered for enhanced performance and various applications to then turn into active free form when applied to the skin and each with a different process for doing so.
You have very different considerations for performance of Vitamin C as an ingredient in skin care compared to when placed on cut fruit. A cut apple does not have the ability of the human to auto regenerate or to produce certain vital cellular responses and benefit from the numerous positive benefits ascorbic acid provides as an ingredient for healthy skin function.
L-ascorbic Acid; Hydrosoluble pH 2.0 - 2.2 Molecular weight 182.08 Base form of ingredient without encapsulation. L-ascorbic acid is difficult to formulate with as not only is it highly unstable with a required low pH not particularly practical for many skin care applications but it oxidates faster. Its small molecular size is also aggressive, therefore considering also that fast absorption in skincare, this is not always the ideal, rather for skin a slower release and improved compatability with certain ingredients to obtain a positive function is desired rather than inflammation and reaction that you don't have to consider with apple flesh.
When applied directly the the apple it successfully prevents the enzymatic process, it is visibly superior as an ingredient for this purpose, as as acid pH this would explain it's efficiency.
Ascorbyl Glucoside; Hydrosoluble pH 2.5 Molecular weight 338.26 The molecule is linked with glucose creating a stable time released form of ascorbic acid. It maintains stability in a fairly wide range of pH and is highly tolerable. When applied it is broken down slowly releasing active ascorbic acid.
In this test it offered same ability to prevent the oxidase as L-Ascorbic Acid. As as acid pH this would explain it's efficiency.
Sodium Ascorbyl Phosphate; Hydrosoluble pH 9.0 - 10.0 Molecular weight 322.05 The molecule is salified and a phosphate group replaced in the cyclic ring, it is a stable and bioavailable form of vitamin C, easily inserted in cosmetic formulations. Sodium Ascorbyl Phosphate is enzymatically broken down on the skin and releases active ascorbic acid.
In this test it offered poor ability to prevent the polyphenol oxidase, as expected given its alkalinity.
Ascorbyl Tetraisopalmitate; Liposoluble pH - Molecular weight 1129.8 The molecule is esterified, rendering it oil soluble like with ascorbyl palmitate, but a step further in providing enhanced permeation and superior stability than it's water soluble cousins. It does not offer anrioxidant activity until the isopalmitate moieties are broken down after application and interaction with human skin releases active ascorbic acid.
Considering skin permeation and effectiveness, its lipid function is key to understanding how it is a superior form and highly stable in terms of a skincare ingredient.
In this test, that focuses on enymatic polyphenol oxidase on a water based subject, it obviously offers little benefit for preventing that visible browning due to its liposolubility.
Yet is no indication of its effectiveness as an antioxidant ingredient due to proven ability to prevent lipid peroxidation.
In conclusion whilat we can understand how this DIY test could be considered a useful tool for marketing purposes by some, but it really cannot seriously be used to demonstrate scientifically the effectiveness of a skincare product containing Vitamin C for its antioxidant ability.
If we had selected a single product with a low pH containing one or even multiple forms of Vitamin C ingredients we would feel it could be inaccurate to use this experiment to demonstrate its relative effectiveness for skin antioxidant benefits.
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