color of the medium changes following N-acetyl Cysteine (NAC) addition - (Nov/10/2007 )

Dear all
When I added NAC (10, 20 30 mM) to my cultured cells in DMEM, the color of the medium changed dose-dependently from pink to yellow. Since NAC pretreatment did not scavenge my drug treatment-induced ROS generation, I do not know whether this color change is normal or due to degradation products of NAC. Althogh I usually prepare NAC solution just before its addition to the medium, I am a little bit worried about the possibility of NAC being degradated. Has anyone out there noticed such color change of the DMEM medium following NAC addition?
thanks

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NAC is an acid. It changes pH and causes phenol red to turn yellow. you can titrate NAC stock solution to neutral pH with NaOH.

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this neutralization will not affect the stability of the stock solution? I mean should it be done immediately before addition to the culture or can I store the neutralized stock solution at - 20?

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Akaline condition will promote S-S formation, neutral pH is OK. Do it before used. Use N2 to remove O2 in order to keep less disulfide formation if you want to make a stock solution.

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