Alpha-Arbutin

Alpha-arbutin inhibits melanin synthesis in cultured human melanoma cells and three-dimensional human skin models, making it a recognized depigmenting and skin-brightening agent. In vitro studies suggest it may be more or less effective than beta-arbutin depending on the cell model used, but no in-vivo (on real people) comparative studies have been identified by the source.

Evidence for superiority over beta-arbutin is conflicting and based solely on in vitro (cell/mouse) studies; no in-vivo human comparative data are cited by the source. Claims of it being "10x stronger" than beta-arbutin are not consistently supported across studies.