Natural Orange 6
|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|
LD50 (Lethal dose)
Except where noted otherwise, data is 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 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. Water hyacinth has various uses, its flowers are processed and used as dye for fingers and toenails . Also, India have been using Eichhornia crassipes plant in dying fab, . In Japan, =same plant is used to paint nails. And in Asia, plant is used as a substitute for Henna. A molecule chemically known as hennotannic acid which are the component of Lawsonia inermis or commonly known as Henna, contains a red-orange, violet, and pink pigment usually used as a dye is also found in Eichhornia crassipes (water hyacinth) flower. The said substance has an affinity to bind protein that makes it a good source in dying skin, fingernails, hair, leather, even silk and wool. Eichhornia crassipes contains active compounds such as lawsone and flavonols, the components found in Henna which allows it to stain skin, hair, and other materials since these chemicals bind well to protein, particularly the keratin in skin and hair.
- 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.