My beloved is a bouquet of henna flowers in the vineyards of Ein Gedi
-Song of Songs 1:14
Henna (Mehndi in India) is a pigment often associated with bridal adornment and ceremonies. The traditionalnames identify the plant, the dye it yields and tattoo-like skin decorations itis used for. A botanical name was given by 18th century Swedish taxonomistCarl Linnaeus, who named the plant “Lawsonia inermis” after a friend. Thebotanical name somehow does not inspire the romantic associations of the traditionalnames that predate Linnaeus and Lawson by a few years!
The ingredient responsible for henna’s orange colour is called lawsone, another uninspiring name. It is a naphthoquinone, a class of molecule with a huge range of bioactivities. One of the most important naphthoquinones is phylloquinone, ubiquitous in green leaves and algae, functioning to transfer electrons out of Photosystem I for use in photosynthetic CO₂ fixation. The exact same molecule rebranded as Vitamin K is injected routinely into new-borns to reduce risk of life-threatening bleeds.
When henna is used to dye skin and hair, lawsone binds stronglyto the structural protein #keratin. Though most people can use henna without areaction, it can sometimes cause contact dermatitis.
Lawsone is actually rather toxic; on the skin this may be an advantage, as the toxicity is also antibacterial and antifungal. Despite the toxicity, henna extract appears to have potential as a phytomedicine for internal use and maybe even as an industrial product for inhibiting metalcorrosion.
So to conclude, henna is wonderful and romantic but optional. But since we have also been talking about naphthoquinones, those of us now past our neonatal Vitamin K shots should remember to top up regularly on greenvegetables.
Sources
LÓPEZ et al: BIOLOGICAL PROPERTIES AND SYNTHESIS OF LAWSONE ANDDERIVATIVES- A STRUCTURED REVIEW. Vitae [Internet]. 2014 Dec; 21( 3 ): 248-258. http://www.scielo.org.co/scielo.php?script=sci_arttext&pid=S0121-40042014000300010
Zumrutdal & Ozaslan, 2012. A Miracle Plant for the Herbal Pharmacy; Henna (Lawsonia inermis). Internat. J. Pharmacol., 8: 483-489. https://scialert.net/fulltext/?doi=ijp.2012.483.489
