What is the best alternative to alpha lipoic acid? What glutathione/antioxidant combination should I take for best whitening?

Thanks for your query. You can switch to reservatrol. It is a potent antioxidant and is a very good alternative for ALA. coQ10 and milk thistle are also good options. The entire mixture is good for you. Hope it helps

All The Best

Glutathione causes skin lightening by preventing the oxidation of tyrosine through its ability to reduce free radical formation in the body.  
Tyrosine oxidation increases the melanin pigment giving the skin its colour. Precursors that stimulate  the body to synthesize its own glutathione naturally are the best effective ways to supplement glutathione.
Some of the glutathione precursors  include N-acetyl cysteine, alpha lipoic acid, B vitamins, selenium and milk thistle. 
The recommended protocol is :
N acetyl cysteine - 500mg along with vit c 1000mgVit E 200 IU, Alpha lipoic acid - 100mgSelenium - 50mcgMilk thistle - 50mgCoQ10 - 15mgL glutathione - 200mg. Can add vit B and D supplements as well.
You can add selenium instead of ALA .  
Best results can be acheived safely by following these under your physician's guidance.