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  • vitamin c serum

    Posted by zuzig on July 11, 2018 at 5:14 pm

    Hi, I have a vitamin C serum  (oil, no water) with 5% ascorbyl tetraisopalmitate and I performed a test with an apple to see the antioxidant activity. The apple turned brown. Does this test have some sort of validity? The serum is oil only, no water. Thank you for your opinions.

    Dr Catherine Pratt replied 4 years, 10 months ago 5 Members · 7 Replies
  • 7 Replies
  • Sibech

    July 11, 2018 at 5:41 pm
    Assuming you want to test for the antioxidant capacity you should know that the browning of apples is an enzymatic reaction and not just free oxygen.
    As for the validity, it can say if your serum can keep apples from browning and that is about all.

  • zuzig

    July 12, 2018 at 7:19 am

    Thank you very much for your answer. 
    So would you say, that I could judge the potency of different vitamin C serums by this test on apples, or? I have compared too samples of grated apples, one I treated with drops of the oil serum I mentioned and the other by ascorbic acid diluted in water (200 mg/30 ml of water) - the one treated with ascorbic acid diluted in water did not brown at all. So the high concentration of ascorbic acid and high acidity of the solution inhibited completely the oxidation thus the enzymatic reaction? Does this other oil serum which did not inhibit the oxidation processes can be considered as not potent enough?

  • EVchem

    July 12, 2018 at 11:38 am

    I think @Sibech is exactly right: 

    As for the validity, it can say if your serum can keep apples from browning and that is about all.

    Also consider that apple tissue is going to be water-based, so a water-soluble ingredient would penetrate for any kind of reaction better than oil-soluble ones. Apple tissue is not like human skin, potency of a serum will ultimately come down to how the human body processes it right?  

  • Sibech

    July 12, 2018 at 2:41 pm

    @zuzig I don’t think you can judge the antioxidant capacity or potency of a cosmetic product with any foods (or any easily doable-at-home experiments).

    the antioxidant function of ascorbic acid in apples is by virtue of pH denaturing the enzyme (grated apples brown more quickly because more enzyme is released compared to cut apples).

     I would suggest doing a test for UVB induced oxidative stress in vitro to see If the product worked.

    I do however think the apple test would make for an app(l)ealing (sorry for the pun) marketing story, however then you would need the active to be oil soluble with a partition coefficient favoring the water phase. I am not in marketing and could be wrong on that part.

  • Vnnil

    July 12, 2018 at 8:35 pm
    Hey @zuzig,
    I don’t think you could judge the efficacy of VC-IP based on the apple experiment.
    Since the VC-IP molecule has been esterified (to enhance skin permeation and stability), it shouldn’t have antioxidant activity until it has gotten rid of the isopalmitate moieties (which should happen in human skin).

  • zuzig

    July 13, 2018 at 7:34 am

    Thank you people for sharing your brain powers:).

  • Dr Catherine Pratt

    July 16, 2018 at 6:47 am

    BTW Vitamin F is supposed to give you essential PLUMPING! Ha!