How to prevent Hydroquinone cream from oxidation during manufacturing and storage? The colour of my cream changes to brownish. However, the assay value does not decrease in stability.
These ref might help!
1. Studies on Hydroquinone and Antioxidants - Natural News
science.naturalnews.com/H/Hydroquinone_and_Antioxidants.html
Comparison of antioxidant activity of extract from roots of licorice (Glycyrrhiza glabra L.) to commercial Antioxidants in 2% Hydroquinone cream.
2. Comparison of Antioxidant Activity of Green Tea Extract to ...
www.tandfonline.com › List of Issues › Table Of Contents
by K Morteza-Semnani - 2007 - Related articles
Oct 17, 2008 - Comparison of Antioxidant Activity of Green Tea Extract to Commercial Antioxidants in 2% Hydroquinone Cream. Download full text.
3. Int J Dermatol. 2003 Dec;42(12):966-72.
Safety and efficacy of 4% hydroquinone combined with 10% glycolic acid, antioxidants, and sunscreen in the treatment of melasma.
Guevara IL1, Pandya AG.
You need to add antioxidant to your formula (e.g butylated hydroxyanisole, butylated hydroxy toluene, sodium metabisulphite, or any other antioxidant that is compatible with your formulation) & if you can purge with nitrogen while preparation or mixing will be more protective.
There are some antioxidants that could prevent this oxidation. The best synthetic ones are: TBHQ, BHT and BHA. There are anther from vegetal source, such as,: tocopherols, rosemary extract, tocotrienols, but these used to be weaker than the synthetics.
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