Alpha ArbutinvsLactic Acid

Alpha arbutin (4-hydroxyphenyl-alpha-D-glucopyranoside) is a glycosylated hydroquinone with glucose bound to the para position. Alpha-glucosidase and other glycosidases slowly hydrolyze the bond, releasing hydroquinone in controlled low concentrations—avoiding peak levels that cause irritation and ochronosis. Released hydroquinone inhibits tyrosinase by competing with tyrosine and through copper chelation at the catalytic center, reducing L-DOPA to dopaquinone conversion. The alpha anomer provides greater stability and skin penetration than beta arbutin. May also inhibit melanosome maturation. Gradual release creates sustained low-dose tyrosinase inhibition that brightens over 8-12 weeks with minimal side effects.

Lactic acid (90 Da, larger than glycolic acid) exfoliates via the standard AHA mechanism: chelating calcium at corneodesmosomes and promoting desquamation through protease activation. Unlike glycolic acid, lactic acid is a natural component of the skin's natural moisturizing factor (NMF) and functions as a humectant, drawing water into the stratum corneum through hygroscopic binding. It inhibits tyrosinase enzyme activity in melanocytes, providing mild brightening. At higher concentrations (10%+), lactic acid upregulates serine palmitoyltransferase and glucosylceramide synthase in keratinocytes, stimulating ceramide synthesis and improving barrier lipid composition. It also enhances filaggrin proteolysis to NMF components. This dual action—exfoliation plus barrier support—makes it the most moisturizing AHA and clinically useful for dry, sensitive, or barrier-compromised skin.