How good of an lightening agent is it.

bearberry = arbutin & methylarbutin

arbutin = beta-arbutin

alpha-arbutin = synthetic arbutin, doesn't oxidise readily to hydroquinone, but not very effective either in the skin

deoxyarbutin is another synthetic arbutin
but, too bad its patented, since its not in any products on the market yet. It is reputed to be 350 times more effective than arbutin, 150 times more effective than kojic acid, 10 times more effective than hydroquinone!

Alpha Arbutin is by far the most effective at skin lightening in comparison to 'regular' Arbutin. Scientific research has proven that it's 10 times as "powerful" as Beta-Arbutin, or in other words the naturally derived Arbutin compound found in bearberry, pear skins, and several other plants.

Alpha-Arbutin also has the ability to limit skin darkening, such with it's ability to hamper the effects of UV radiation on the skin, and regular tanning.

Quite honestly, I'd go as far as to noting Arbutin as one of the leading, most effective natural and safe skin lighteners around. I wouldn't consider Deoxy-Arbutin a choice when it comes to skin lightening at this point; not only does it not exist to the public, but I doubt that it's "10 times as effective as Hydroquinone" while being "350 times as strong as Arbutin" at the same time.