Couple questions about gluconolactone, for it to be an active PHA does is need to be at the same pH as AHAs? Or can it be at around a 5 and still be ok?
My supplier has a suggested usage rate at 1-5% but all the studies I have read are at the very least 10% gdl. Ive even seen it being used as 30% in some products on the market formulated by some reputable chemists. So I know its only the suggested usage rate being provided - but because of studies and products by reputable chemists, can I assume its safer to use over 5%.


  • Perry, If you see this discussion I attended your webinar and asked a little bit about this and you suggested I check the CIR. Which I did but then came up with this :/
  • PharmaPharma Member, Pharmacist
    PHA are prossibly safer and milder due to their larger molecules and stronger interactions with hydrophilic groups which results in a slower, less efficient, and less deep skin penetration.
    Efficacy with all acid peels depends on pH; the lower, the more aggressive. If you have a high degree of salt instead of free acid, your skin can handle way higher amounts. Given that the different acids likely have different modes of action (of which we don't even know or understand all) makes predictions difficult.
  • siouxchemsiouxchem Member
    edited February 12
    @Pharma I understand its safer and milder which is why I am formulating with it. Question is, the pH and where it needs to be at in order for it to be 'active' as a PHA. As I understand the pH of glycolic or lactic needs to be at < 3.85 to be 50% active and sa needs to be at < 3. 
    Also, my supplier said 1-5% but all studies have it at 10% or higher in a formulation and I have seen reputable chemists use it at 30%. 
  • PharmaPharma Member, Pharmacist
    The issue is that too often people think 'more is better'... What do you do? You add more (at least of the cheap ingredients) and make sure it's not going to backfire (with hydroxyacids, this means increasing pH).
    Do you intend on using it for yourself or for sales? If only for yourself: go low (% wise), go slow and see how your skin takes it and how well it can handle low pH. Go from there, play with lowering pH or increasing %.
  • siouxchemsiouxchem Member
    edited February 9
    @Pharma I literally just want to know the pH for GDL to be at least 50% bioavailable 
     :D I was just looking for answers to my original questions haha

  • PharmaPharma Member, Pharmacist
    Given that you don't eat GDL, bioavailability isn't a term which applies.
    See, you could have 100% 'bioavailability' (skin penetration) without any effect or you can have zero availability but a full effect on the dead uppermost keratinocyte layer. Depends also on your definition of 'effect'... cause PHAs can have a set of different effects, some biological/pharmacological, others chemical/physical.
    If you did a silly short-circuit calculation you would assume that 50% bioavailability is achieved at 50% non-deprotonation which would correspond to the pKa value of gluconic acid (which is BTW 3.86). Using the same assumption, a pH of 4.86 would result in only 10% 'activity' and a pH of 5.86 1%. Because life is never simple, this is just a oversimplification which is highly likely not going to tell you anything beyond an estimation of skin tolerability at a given concentration. As usualy with cosmetics: You'll have to try because current maths just doesn't suffice to predict such complex systems.
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