My first tattoo

This weekend I had my first experience with henna.  As I chemist, I felt I should know more about this fascinating tradition.  I am a believer in the power of symbols, and I chose a peacock for my design.  A friend painted it on my ankle using a pre-mixed paste.  I use the word "paint" loosely here, the henna paste was more like frosting that was carefully squeezed out of a tube.  The paste was thick and very dark in color.  I let it sit uncovered for about 2 hours.  Then I doused a paper towel with lemon juice and sprinkled copious amounts of granulated sugar on the moist paper towel.  I gently covered the tattoo with the paper towel and wrapped it in saran.

After I got home, I looked up more about henna tattooing and read that the color transfer is enhanced by heat so I microwaved a wet bandanna and wrapped it around the saran wrap.  I also read that the dry paste should be allowed to remain in contact with the skin for 4 hours but the longer it stays the darker your tattoo will result.  Therefore, I didn't scrape the paste off until morning.  I also read that the tattoo color develops (darkens) gradually so if it isn't as dark as you would like right away, you must be patient.

I wonder if the active dye in henna, Lawsone (2-hydroxy-1,4-naphthoquinone or hennotannic acid), has ever been used for cell staining in microscopy.  The molecule (CAS No. 83-72-7) has 1,965 citations in SciFinder and can be purchased at 93 commercial sources.  Searching for reactions where Lawsone is a reactant yields 3,617 reactions.  Considering this molecule, isolated from the Henna plant (Lawsonia inermis), has been used in body art for the past 5,000 years it makes sense that Lawsone has been well-studied.

From a quick search, it appears that Lawsone readily attaches to free amino acids and proteins in the skin and hair.  It has been used for fingerprint staining on paper as well as protein quantitation by spectrophotometry. I will have to look into the chemistry more deeply at a later date. I keep reading that the Lawsone molecule reacts with free amines via Michael addition, resulting in a strong permanent stain, but I can't picture the mechanism myself.

The peacock symbolizes integrity, guidance, protection and watchfulness.  It is said to breathe life into your faith and rejuvenate self-esteem.  Since the peacock replaces his feathers annually, it is a symbol of renewal. Due to its similarity to the phoenix, it also represents resurrection or rebirth. The "eyes" in its feathers were thought in Egyptian, Greek, and Roman mythology to be all-seeing.  I chose a side-view (modest) image of the bird, rather than a forward-facing display of plumage.  I think the demure, yet proud, image better suits me.  I like the way its posture connotes alertness.

Oh, and if you haven't seen my ChemChamps video yet, please watch!  I only have 4 more days to peacock my way into the top 10 for a chance to get special training in science communication at the American Chemical Society national meeting in San Francisco (August 2014).

References

Pradhan, et al. From Body Art to Cancer Activities: Perspectives on Medicinal Properties of Henna. Current Drug Targets, 2012, 13, 1777-1798.

Jelly, et al. Lawsone: A Novel Reagent for the Detection of Latent Fingermarks on Paper Surfaces.  Chemical Communications, 2008, 30, 3513–3515.

Giri Dev, et al. Dyeing and Antimicrobial Characteristics of Chitosan Treated Wool Fabrics with Henna Dye.  Carbohydrate Polymers, 2009, 75, 646-650.