Natural Orange 6
|Molar mass||174.15 g/mol|
|Melting point||195 to 196 °C (383 to 385 °F; 468 to 469 K) (decomposition)|
|almost insoluble |
|R-phrases||R36 R37 R38|
|S-phrases||S26 S36 S37 S39|
|Lethal dose or concentration (LD, LC):|
LD50 (Median dose)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is: / ?)(|
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 in the flower of water hyacinth (Eichhornia crassipes). Humans have used henna extracts containing lawsone as hair and skin dyes for more than 5000 years. Lawsone reacts chemically with the protein known as 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 and sunscreens. Chemically, lawsone is similar to juglone, which is found in walnuts.
- Merck Index, 12th Edition, 5406.
- MSDS at Physical & Theoretical Chemistry Laboratory, University of Oxford
- Dweck, A. C. (2002). "Natural ingredients for colouring and styling". International Journal of Cosmetic Science 24 (5): 287–302. doi:10.1046/j.1467-2494.2002.00148.x. PMID 18498522.
- Sakunphueak, A.; Panichayupakaranant, P. (2010). "Simultaneous determination of three naphthoquinones in the leaves of Impatiens balsamina L. by reversed‐phase high‐performance liquid chromatography". Phytochemical Analysis 21 (5): 444–50. doi:10.1002/pca.1216. PMID 20931623.