4-n-butylresorcinol (4NB) in the treatment of pigment disorders (For Professionals)

• The authors seek to measure the effet of  4-n-butylresorcinol to treat pigmented spots by comparing it with hydroquinone, arbutin and kojic acid.

Hypothesis:

• Tyrosinase is the enzyme enabling the production of melanin.
• Many studies only investiage tyrosinase in mushrooms and mice melanoma cells
• These substances are not necessarily inhibitors of human tyrosinase

Study

• Comparison of hydroquinone, arbutin and kojic acid with 4-n-butylresorcinol (4NB)

In vitro (Results):

• biochemical assay of the human tyrosinase enzyme:

1. arbutin and hydroquinone are the least effective and have an EC50 (inhibition of 50% of the activity of tyrosinase) reached with a necessary concentration of 1 milliM (1000 microM)
2. kojic acid is 10 times more potent with an EC50 reached at 500microM
3. 4NB shows an EC50 of 21microM

• inhibition of the production of melanin in melanocytes cultures and in artifical skin cultures (Melanoderm, MatTek ®):

1. Arbutin is the less potent with an EC50 over 5000 microM
2. Kojic Acid has an EC50 at 400microM
3. Hydroquinone has an EC50 at 40 microM
4. 4NB has an EC50 at 13.5 microM

• then application was done in vivo on 14 women aged between 55 and 69 comparing formulations of the same brand.

Comments

• Hydroquinone is the treatment of choice in hyperpigmentary disorders (especially true for melasma (chloasma, pregnancy mask).
• Strangely enough, in this study it was ineffective in vitro (it would not inhibit tyrosinase according to the authors !)…although it is effective in vivo  when treating non specified pigmentary disorders (“age spots”)
• The clinical part of the study consists of treating pigment lesions (non specified) on the forearms. Different pigmentary disorders have very different molecular dysfunctions and even if the spots on the forearms could be lentigos, they could also be seborrheic keratosis (flat, acanthotic, hyperkeratotis), melasma (chloasma, pregnancy mask), post-inflammatory hyperpigmentation…
• There are no substances compared in vivo to 4NB. They were compared in vitro only. (in vivo=in humans)

Source of Information: 2012 (09) – Kolbe. L 21st Annual Congress of the EADV (European Academy of Dermatology and Venerology) – Prague (Praha), Czech Republic (česká republika)