2-Mercaptonicotinoyl glycine prevents UV-induced skin darkening and delayed tanning in healthy subjects: A randomized controlled clinical study

J Cosmet Dermatol. 2024 May;23(5):1745-1752. doi: 10.1111/jocd.16200. Epub 2024 Feb 19.

Abstract

Background: Chronic nonextreme sun exposure induces two mechanisms of skin pigmentation, causing immediate darkening and delayed tanning. A new molecule, 2-mercaptonicotinoyl glycine (2-MNG), has been shown in vitro to inhibit both immediate darkening and new melanin synthesis via covalent conjugation of the thiol group of 2-MNG to melanin precursors.

Objective: To evaluate 2-MNG in preventing both mechanisms in vivo.

Methods: In a randomized, intra-individual and controlled study, 33 subjects with melanin-rich skin were exposed to UV daylight on designated areas on the back and treated with a cosmetic formula containing 0.5% or 1% 2-MNG alone or 0.5% 2-MNG in association with lipohydroxy acid (LHA, 0.3%) plus Mexoryl-SX (MSX, 1.5%). The respective vehicles were used as controls and 4-n-butyl-resorcinol (4-n-BR, 2.5%) as a positive reference.

Results: 2-MNG alone significantly reduced immediate darkening and inhibited new melanin production when compared with vehicle, with higher performance at 1% than at 0.5%. 2-MNG at 0.5% in association with LHA and MSX showed significantly higher performance than 2-MNG 0.5% alone. 2-MNG at 0.5% and 1% showed significantly better performance than 4-n-BR.

Conclusions: 2-MNG inhibited both UV-induced skin pigmentation mechanisms in vivo. The association of 2-MNG with LHA plus MSX showed the highest efficacy on melanin-rich skin with pigmentation induced by UV exposure.

Keywords: anti‐oxidation; anti‐pigmenting; mercaptoniacinamide (2‐MNG); topical.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Female
  • Glycine* / administration & dosage
  • Glycine* / analogs & derivatives
  • Glycine* / pharmacology
  • Healthy Volunteers
  • Humans
  • Male
  • Melanins / radiation effects
  • Middle Aged
  • Skin / drug effects
  • Skin / metabolism
  • Skin / radiation effects
  • Skin Pigmentation* / drug effects
  • Skin Pigmentation* / radiation effects
  • Sunbathing
  • Ultraviolet Rays* / adverse effects
  • Young Adult

Substances

  • Glycine
  • Melanins