Being of Bengali-British decent, there always have been two distinct parts of my identity. The one where I am to deeply relate to the struggles of a Bollywood protagonist being married off, and the other where I deeply love a morning cuppa. Having the best of the both worlds doesn’t come without its challenges of course, especially when ideological clashes can happen.
However, one aspect of Bengali culture – the use of henna – to either adore the hands of a bride or to dye the hair a range of colours is distinctly part of my ancestry. Just as before a big event of any kind, people tend to paint their nails a myriad of colours, within Islamic cultures, henna is used as part of the beautification process which all genders can partake in.
Henna has been particularly popularised for its use as a “temporary tattoo” within mainstream culture as many high-profile celebrities have been seen to wear it. The orange-red tint that henna leaves behind on its wearers is mainly due to the compound lawsone present. Not only its colour, but other potential medicinal aspects of lawsone have been utilised by various cultures in different timelines too.
Centuries of Use
The earliest recorded use of henna comes from Ancient Egypt where mummies were found to have henna-dyed hair and finger tints. Further analysis has confirmed the presence of hydroxynaphthoquinone (lawsone), the active ingredient within henna1. However, it is important to note that henna has not only been used for cosmetic purposes in ancient cultures of North Africa and Asia, but has also been utilised for its physiological and medicinal benefits too2.
It is however, important to note that the historical use of henna is not tied to a single religion or culture but instead, spans a wide variety of communities. Henna, however, has seen a modern mainstream use especially within Western circles with celebrities such as Vanessa Hudgens, Beyonce and Tan France choosing to decorate themselves in various designs.
Henna, used in dyes and for temporary tattoos come from the leaves of the bushy, flowery henna plant and is known within scientific circles as Lawsonia inermis (Figure 1)3. This plant is commonly found in Australia, Asian and along the coasts of Africa4.
Although there are about 70 compounds which have been isolated from this plant alone, only one, Lawsone (Figure 2)5, has been linked to dyeing and medicinal aspects of the plant2.
Lawsone is part of a group of chemicals called naphthoquinones which are aromatic compounds that are present throughout nature and can be found in many plants, fungi, algae and bacteria 6. Aromatic compounds are structures which have the hexagonal shape of bonds as shown in the image.
Naphthoquinones are known to be highly reactive and unsurprisingly, when used as a natural or synthetic dye range from the colours of yellow to red.
Hands & Hair
When applied to the skin, lawsone is able to the stain the area with an orange-red hue which can be used to produce intricate pattens that can last from days to weeks7. However, when applied to the hair, lawsone is able to create a rich colour which can last a couple of months.
The way in which lawsone stains both the hair and the skin are due a specific chemical reaction taking place. Lawsone, the dyeing agent within henna, is able to chemically react with the protein, keratin found in both the hair and skin. This chemical reaction is known as a Michael addition, which is able to form carbon-carbon bonds between compounds, thereby resulting in the strong staining of the skin or hair8.
It is however, important to note that lawsone is thought not to penetrate the hair fibre like box dyes but instead, settles on the top thereby retaining the natural oils and structure of the hair9,10.
More than tattoos and hair-dye?
As noted previously, henna has been utilised by ancient civilisations both dye the hair and nails but is has been used for therapeutic purposes. Within traditional medicine, henna has been used to heal spleen diseases, bronchitis and infections of the eyes and intestines11.
Specifically, lawsone is thought to bring about the main therapeutic benefits. Various modern studies have aimed to quantify the antibacterial effects that lawsone has shown against various microorganisms. This is great interest due to the rising tide of antibiotic resistance.
Interestingly, one study found that the growth of E.coli, bacteria that can cause urinary tract infections, was inhibited by increasing the concentration of the herbal powder extracted from henna12. The antibacterial effects observed by lawsone and other naphthoquinones have strong biochemical processes lying at its surface, from its ability to inhibit replication to disturbing the respiration reactions within microbes.
Similar results has been found with other strains of bacteria, confirming the antibacterial activity of henna leaves, which supports its use within traditional circles13. The use of medicinal plants to ease certain illnesses plays a pivotal role in covering the basic health care needs within developing nations, presenting a requirement to validate and document these medicinal benefits, if any14.
This is an important discovery to note as drug discovery processes have great potential to start within Mother Nature itself. Discovering and isolating ingredients to use in drug design from nature has been utilised in various instances, the most notable of which is the isolation of morphine, from opiate poppies, which is used to treat pain15.
Duality of Henna
Henna, and lawsone for that matter is a multifaceted molecule which is steeped in both deep various cultural roots and its documented pharmacological effects.
From the distinct colour to smell, henna has been utilised over the centuries as a tool to beautify and heal individuals. The use of henna is even woven into scriptures, presenting its longstanding use within various cultures and religions. Although, henna might not be prescribed at the pharmacy today, it is of great interest to researchers studying tropical medicines as it has been used throughout history to ease certain ailments. There is hope by studying and quantifying these effects, if any, that it has the potential to aid future drug discovery processes and validate its use within developing nations.
Note: It is imperative that you DO NOT use henna which contains PPD (known as black henna) , especially within children due to potential allergic reactions. For more information and targeted advice please visit:
Tan France with henna: by https://www.refinery29.com/en-us/2018/10/215372/tan-france-gray-hair-house-99-grooming-interview
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