- Lawsone
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Lawsone[1][2] 
2-Hydroxy-1,4-naphthoquinoneOther namesHennotannic acid
Natural Orange 6
C.I. 75480Identifiers CAS number 83-72-7 
PubChem 6755 UNII TLH4A6LV1W 
ChEMBL CHEMBL240963 Jmol-3D images Image 1 - O=C(C(O)=C1)C2=C(C=CC=C2)C1=O
Properties Molecular formula C10H6O3 Molar mass 174.15 Appearance Yellow prisms Melting point 195-196 °C (decomposition)
Solubility in water almost insoluble [3] Hazards R-phrases R36 R37 R38 S-phrases S26 S36 S37 S39 LD50 100 mg/kg Related compounds Related naphthoquinones Juglone 
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)Infobox references Lawsone (2-hydroxy-1,4-naphthoquinone), also known as hennotannic acid, is a red-orange dye present in the leaves of the henna plant (Lawsonia inermis) as well as jewelweed (Impatiens balsamina).[4] Humans have used henna extracts containing lawsone as hair and skin pigments for more than 5000 years. Lawsone reacts chemically with the protein keratin in skin and hair, in a process known as Michael addition, resulting in a strong permanent stain that lasts until the skin or hair is shed. Lawsone strongly absorbs UV light, and aqueous extracts can be effective sunless tanning sunscreens. Chemically, lawsone is similar to juglone, which is found in walnuts.
References
- ^ Merck Index, 12th Edition, 5406.
- ^ MSDS at Physical & Theoretical Chemistry Laboratory, University of Oxford
- ^ http://msds.chem.ox.ac.uk/HY/2-hydroxy-1,4-naphthaquinone.html
- ^ Dweek, A. C. (2002). "Natural ingredients for colouring and styling". Int. J. Cosmetic Sci. 24 (5): 287–302. doi:10.1046/j.1467-2494.2002.00148.x. PMID 18498522.
External links
Categories:- Aromatic compounds
- Natural dyes
- Naphthoquinones
- 2-Naphthols
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