What-it-does: antioxidant, skin brightening

An optical isomer of naturally occurring arbutin (or beta-arbutin). Just like its sibling, alpha-arbutin is also a skin-brightening, depigmenting agent.

Researching the difference between the two kinds of arbutin, you can read in multiple places on the internet that alpha-arbutin is stronger in effect. Unfortunately, it's never backed up with a credible source. :(  Our own research resulted in conflicting results: a study from 1995 found that alpha-arbutin is 10x as effective on mouse melanoma as beta-arbutin. On the other hand, a more recent study from 2015 found that beta-arbutin is more effective both on mouse melanoma cells and on human melanoma cells (btw, kojic acid was the most effective on human melanoma cells).  

None of the studies we could find is in-vivo (made on real people) anyways, so who knows. We think you cannot go wrong with trying both beta- and alpha-arbutin and see if one works better for you than the other.