Lawsone[1][2]
IUPAC name	2-Hydroxy-1,4-naphthoquinone
Other names	Hennotannic acid Natural Orange 6 C.I. 75480
Identifiers
CAS number	83-72-7
PubChem	6755
SMILES	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)
Hazards
R-phrases	R36 R37 R38
S-phrases	S26 S36 S37 S39
LD50	100 mg/kg
Related compounds
Related naphthoquinones	Juglone
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 balsamica).^[3] 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.

[edit] References

1. ^ Merck Index, 12th Edition, 5406.
2. ^ MSDS at Physical & Theoretical Chemistry Laboratory, University of Oxford
3. ^ Dweek, A. C. (2002). "Natural ingredients for colouring and styling". Int. J. Cosmetic Sci. 24: 287–302. doi:10.1046/j.1467-2494.2002.00148.x. 

[edit] External links

• Lawsone on the Henna Page