The term henna refers to the extract of the Lawsonia inermis L. plant used for hair care and coloring, as well as for other therapeutic purposes. The most important active ingredient is the lawsone, present at concentrations varying between 0.55% and 1%. Let's find out better.
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Where is the Henné
The henna plant is native to Africa and Asia. It is a helpless shrub as a young and thorny in adulthood due to the hardening of the branches, belonging to the Lytraceae family; up to 6 m tall, it has opposite leaves, oblong or lanceolate and white and small flowers, gathered in panicles, fragrant. It is native to northern and eastern Africa and western and southern Asia, widespread, following cultivation in all tropical areas.
The drug consists of dried leaves .
Its use is very ancient, it was used already in the times of the Egyptians to dye the mummies; in the Middle East, the Far East and North Africa it has always been used as a dye for nails, hands, hair, clothes, etc. In Europe, for some years this product, alone or mixed with walnut husk and gall nuts, serves as a dye especially for female hairstyles.
The main active ingredient (colorant and pharmaceutical) is represented by the lawsone, 2-hydroxy-1, 4-naphthoquinone, structurally similar to juglone (5-hydroxy-1, 4-naphthoquinone), the coloring substance of the walnut husk. In addition to this substance, gallic acid, tannins, resins and sugars are present in the drug.
The lawsone is not present in the bark, stem or root of the plant. The concentration varies in the leaves with temperature and climatic conditions: plants that grow in warm places have a higher concentration of lawsone .
The lawsone appears to be a product of the degradation and auto-oxidation of primary glycosides called hennosides A, B and C.
On the market it is possible to find henna especially as a powder.
Cosmetic use of Henné
Henna is used for the care and natural coloring of hair as well as for coloring of hands and body.
Henna is used in Arab countries especially for the care of the hair, in fact, penetrating into the structure of the hair, it binds to keratin and gives the hair brightness and strength.
To prepare a long-lasting color, the mixing of henna must be made slightly acid (about 5.5) by adding a weak acid such as citric acid, boric acid or adipic acid. Acidification can take several hours depending on the outside temperature.
Also the application on the hair must be prolonged, to allow the active principle to penetrate into the hair structure.
Let's discover the vegetable colors for hair
Pharmacological use of Henné
Henna leaves also show anti-fertility activity. The flowers and fruits are considered emmenagogues (they stimulate menstruation). The lawsone has an antifungal, antibacterial, antitumor, antispasmodic and mild activity of Vitamin K.
Contraindications of Henné
Not recommended for internal use, during pregnancy and lactation .
For external use and for coloring hair, prolonged use may change the color, making it turn towards red-orange, unless henna is mixed with other plants to obtain different nuances.
