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), for which it is named, as well as in the common walnut (Juglans regia)[5] and water hyacinth (Pontederia crassipes).

Darker colored staining is due to more lawsone–keratin interactions occurring, which evidently break down as the concentration of lawsone decreases and the tattoo fades.

[7] Lawsone strongly absorbs UV light, and aqueous extracts can be effective sunless tanning agents and sunscreens.

Isolation involves four steps: During the rinse, the lawsone will be the bottom as it has such a high density and the chlorophyll molecules will all be on the top of the mixture.

[11] Lawsone shows promise as a reagent for fingerprint detection because of its photoluminescence maximized at 640 nm, which is high enough that it avoids background interference common for ninhydrin.