Table 1.

Classification of hypopigmenting agents based on reported mechanisms of action.

Mechanisms of Action	Hypopigmenting Agent
Before melanin synthesis
Regulation of tyrosinase transcription	TGF-β1, TNFα, IL-1α, IL-1β, IL-6, Lysophosphatidic acid, C2-Ceramides, Sphingosine-1-phosphate, Sphingosylphosphorylcholine, Tretinoin
Inhibition of tyrosinase maturation	Glucosamine, Tunicamycin, Glycosphingolipid, Calcium D-pantetheine-S-sulfonate
During melanin synthesis
Inhibition of tyrosinase activity	Hydroquinone, Arbutin, Kojic acid, 4-n-Butylresorcinol, Phenolic compounds, 4-Hydroxyanisole, Methyl-gentisate, 4-S-CAP & derivatives, Ellagic acid, Oxyresveratrol, Resveratrol, Aloesin, Azelaic acid, Zinc
After melanin synthesis
Post-transcriptional control of tyrosinase	Linoleic acid, α-Linolenic acid, Phospholipase D2
Inhibition of melanosome transfer	Niacinamide (Vitamin B3), serine protease inhibitors, lecthins and neoglycoproteins, RW-50353, soybean.milk extracts
Regulation of melanocyte environment	Corticosteroids, Glabridin
Antioxidants	α-Tocopherol, Ascorbic acid, 6-Hydroxy-3,4-dihydrocoumarins, α-Lipoic acid, Methimazole, Phenol/catechol, Ascorbic acid palmitate, Decursin, L-α TF, VC-PMG, Thioctic acid

TGF = transforming growth factor, TNF = tumor necrosis factor, IL = interleukin, 4-S-CAP = 4-S-cysteaminylphenol, TF = tocopherol ferulate, VC-PMG = magnesium L-ascorbyl-2-phosphate.