thiopyridinone

Thiopyridinone (marketed under the brand name Melasyl) is a novel, multi-patented cosmetic depigmenting agent developed by L'Oreal. Introduced in 2024 after 18 years of research, it represents a new class of skin-lightening molecules designed to address localized hyperpigmentation, including solar lentigines (age spots), melasma, and post-inflammatory hyperpigmentation (PIH). Unlike traditional depigmenting agents such as hydroquinone or kojic acid, which primarily function by inhibiting the enzyme tyrosinase, thiopyridinone operates through a unique "precursor-trapping" mechanism. It specifically binds to and neutralizes reactive melanin precursors, such as dopaquinone, preventing their polymerization into melanin pigments. This targeted approach allows for the effective reduction of dark spots while maintaining a high safety profile across all skin tones and phototypes. The molecule is the key active ingredient in L'Oreal's La Roche-Posay Mela B3 product line.

Brand names

Melasyl

Other names

2-mercaptonicotinic acid2-sulfanylpyridine-3-carboxylic acid2-thioxo-1,2-dihydropyridine-3-carboxylic acid