Tanning In Shade(The Chemistry Behind it)

Ashish KumarMS10043

Points of Discussion:• What is Tanning: The Biochemistry behind it and what actually a tan

is.

• Various Tanning Lotions and how they work especially via Maillard Reaction (Browning reaction, its mechanism and application in food chemistry).

• Role of DHA (Dihydroxyacetone) as a tanning chemical and its use in Cosmetic Industry.

Introduction :• We all know what a tan looks like, we see it every day, its kind of

part of our everyday culture. • Tanning is the process by which the colour of body skin changes to

brown on exposure to the sunlight.• The sunlight triggers the formation of chemicals called melanoidins

in the skin which give it a colour.• The fact is however that, a tan is occurred when the damage is done

to the DNA of the skin cells.

• UV radiations either in form of sunlight or the lamps from the tanning beds, strikes the skin surface. Since it is very harmful to the genetic material of the cells, it causes damage to the DNA of skin cells. This is clearly not a good thing….!!!!!!!!!!!• However, to our advantage, our own body too has

mechanism to counter this grim problem….!!!!!!!!!

• The body sends out an emergency signal. These signals are received by other cells in between skin cells called melanocytes.• These melanocytes, upon receiving the emergency

signal, start releasing a pigment called melanin.• This pigment migrates into the skin cells and protects

the nucleus of the cells. So, it sort of creates an umbrella over the nucleus blocking the UV radiations.

• The fact is however, the damage is already done. The pigment just reduces the further damage. Thus, tanning is actually a sign that we are doing damage to genetic material of our cells.• This is not good clearly as it can cause all kinds of

problems related to the damage of skin as the skin cells simply die. In most cases, the damaged DNA is able to repair itself, but in certain unlucky cases, mutation occurs and the cells grow out of control. Thus, resulting in skin cancer or melanoma.

Is tanning addictive?• The same time as signal goes out to the melanocytes,

the body also receives a boost of endorphins, much like what we talk about the runner’s high. These endorphins make you feel good, make you feel positive.

• But these endorphins also belong to the opiate family, just like heroine and cocaine. These are released in small quantities and overtime body gets dependent on this.• Studies have shown that

people who tan frequently at tanning salons find it difficult to restrain themselves from it, even though being aware of what threats they are exposing to their bodies with each exposure to UV.

• Hence tanning is indeed addictive.

• The skin is made up of different layers of cells, and the outermost layer, the one that faces the world every day, is the stratum corneum. The stratum corneum is made up of dead skin cells that migrate from the layers below. This layer of protective cells is your body’s first barrier against the outside world; it protects the living skin cells underneath.

• One of the key components of the stratum corneum is the keratin protein. Keratin gives the stratum corneum its structure.

Self-tanning Lotions:• Sunless tanning (also known as UV-free tanning, self-tanning, spray tanning,

or fake tanning) refers to the application of chemicals to the skin to produce an effect similar in appearance to a suntan. The popularity of sunless tanning has risen since the 1960s.

• Among today’s bestselling cosmetic are self-tanning lotions.

• Many people across globe Wish to have a tanned skin to flaunt but for that they can’t just go around the Caribbean like Captain Jack Sparrow!!!

• One simple way to do this is sit back and relax in the hot tropical sun. However it does have many disadvantages too like premature ageing and skin cancer due UV radiation.

• However Chemistry here comes to the rescue. Lotions have been developed all over the world that help you attain an authentic tan without actually going into scorching sunlight.• All such lotions have a common key ingredient : DHA

(Dihydroxyacetone) that gives a tan-like appearance without sun exposure and carries less health risks than any of the other available methods. To date, it is the only active ingredient approved by the US Food & Drug Administration (FDA) for sunless tanning.

DHA(Dihydroxyacetone) :• Also known as glycerone, a

simple carbohydrate (a triose) with formula C3H6O3.• Often derived from plant sources such as sugar

beets and sugar cane, and by the fermentation of glycerin.

• DHA is present in tanning products at concentrations between 2 and 5%. The deeper tanning formulas are more concentrated.• The formulations are stable at pHs between 4 and 6.• Above pH 7, brown compounds form in solution, so it

doesn't work as a tanner. Therefore, mixtures sold as tanning agents are buffered to about pH 5.• They are also kept relatively cool, because prolonged

heating to even a little above body temperature affects their stability.

Discovery of DHA as tanning agent:• In the 1950s, Eva Wittgenstein at the University of Cincinnati was

doing research with dihydroxyacetone.

• Her studies involved using DHA as an oral drug for assisting children with glycogen storage disease, i.e. their bodies had difficulty in converting food into energy.

• The children received large doses of DHA by mouth, and sometimes spat or spilled the substance onto their skin. Healthcare workers noticed that the skin turned brown after a few hours of DHA exposure.

• Eva Wittgenstein continued to experiment with DHA, painting liquid solutions of it onto her own skin.

• She was able to consistently reproduce the pigmentation effect, and noted that DHA did not appear to penetrate beyond the stratum corneum.

• It was then found out that DHA reacted with the amino acids present in the skin by a well-known reaction called “Maillard Reaction”.

Maillard Reaction :Louis-Camille Maillard

(1878 - 1936)

Photographed in his laboratory

1915

1912 – 1916: He published 8 papers on his

observations of colour changes on mixing amino acids and sugars.

No one else took much interest in the reaction until 1950s

• Occurs between reducing sugars and amines at high temperatures (Non-enzymatic).

• Produces flavor in foods.• Produces color.• This is the particular reaction

that gives brown colour and aroma to meat and other foods upon cooking. Even, the golden brown colour of the beer is because of it.

•Steps involved in the reaction are:1. Condensation – amines/carbonyl2. Rearrangement – enolization3. Fragmentation4. Strecker Degradation5. Polymerization – brown colour.

Initial Step: Glycosylation

• Reaction between a reducing sugar and primary amino acid.• Loss of water from this molecule results in formation

of an imine that can cyclize into N-glycoside.

N-Glycosylation

Step 2: Amadori Rearrangement

• Instead of cyclisation of immonium ion, a rearrangement called Amadori rearrangement may occur.• Glycosylamines and Amadori products are

intermediates formed during the course of the Maillard reaction.

The Amadori Rearrangement

Step 3: Fragmentation

• In the pH range 4-7, Amadori products undergo degradation to give 1- and 3-deoxydicarbonyl compounds (deoxyosones).

• These Deoxyosones are reactive α−dicarbonyl compounds and give rise to other, secondary products that include furanoses, pyrroles, pentoses, formylpyrroles, etc. These give the aroma and colour to the food.• Pentoses may further react with amines to give orange

dye products, influencing the color of the food.

Formation of Aroma Compounds:

Colored products…

Step 4: Strecker Degradation

• It is a reaction between α− dicarbonyl compounds, such as the deoxyosones formed in the Maillard reaction, and amines.• The aldehyde (referred to as a Strecker aldehyde) and

aminoketone gives rise to strong odors.• Condensation of two aminoketones may yield pyrazine

derivatives that are also powerful aroma compounds.• Common Strecker aldehydes include :1. ethanal (fruity, sweet aroma) 2. methylpropanal (malty)3. 2-phenylethanal (flowery/honey like aroma).

Strecker Degradation

Pyrazine Formation

Step 5: Polymerization

• Last step involves the formation of brown nitrogen-containing pigments (melanoidins) by aldol condensation and polymerization of furfurals.

Temperature dependence of Maillard reaction:• The Maillard reaction occurs at fast rate at high

temperature. It can also occur at low temperature but at slow rates.

So what happens when suntan lotions are applied?• DHA : being a ketose sugar ,which is an active

ingredient of these lotions, reacts with the free amino groups in the skin proteins and particularly by combining with the free guanido group in arginine (Epidermal proteins have a very high content of the amino acids arginine, lysine, and histidine.). This results in formation of a ketoimine.• Later steps of the reaction are not understood

completely as the process is very complicated. However it is surely known that the reaction proceeds as Maillard reaction resulting in products that are cyclic and linear polymers having a yellow or brown color.

• Experimentally, it is found that arginine is the most reactive, with the appearance of a dark brown color within 30 minutes. Aqueous mixtures of DHA with glycine, lysine, and histidine also give brown to yellow pigments. All these pigments are called melanoidins which give the skin characteristic brown color or tan.

Factors affecting DHA tan :• DHA reacts slowly with the stratum corneum. The tan's

intensity depends on the type and thickness of the skin layer. Where the stratum corneum is very thick (at the elbows, for example), the tan is intense. Where the horny layer is thin (such as on the face) the tan is less intense.• pH : Another important factor in a DHA tan is the pH levels

of the skin and formulation. An alkaline pH turns the tan orange, whereas a slightly acidic pH reduces color problems. • The tanning reaction does not depend on UV rays.• In vitro tests show that the amount of water is important in

the tanning reaction. A surplus of water hinders the reaction.

Advantages of DHA?• Fast browning or tanning of the skin.• The tanning occurs on the stratum corneum and since

this layer of skin falls off and is regenerated, the tan acquired is just temporary (5-7 days of application). Advantage??? Well depends if you want a temporary tan to show off!!!!!!! • DHA doesn't penetrate any further than the stratum

corneum. •  Contact dermatitis caused by DHA has rarely been

reported. Most causes of sensitivity are due to other ingredients such as preservatives in the preparation.

Disadvantages of DHA?• Most of the time irregular tanning is observed. Infact,

on initial launch of lotions and sprays containing DHA in 1970s, off-color orange was observed!!!!!! The cosmetic industry has come far from then and so have these products now producing authentic tan.• DHA containing lotions don’t offer any protection

against UV. So one still has to apply a sunscreen. Other tanning chemicals like melanobronze offer UV protection as they artificially trigger melanin production from melanocytes.• Some concerns are raised from recent studies of

inhalation and ingestion of DHA. So, better keep them out our eyes and mouth.

Undesirable staining Darkened scaly lesions

Peeling

Conclusion:• Thus we saw how the tanning occurs and what is the chemical

reactions behind it.

• The use of DHA is common and too a large extent safe in suntan lotions.

• So if you desire to have a tan then no need to go out in sun, just apply such DHA containing lotions, sit back and relax on your couch watching your favorite TV show whole afternoon.

Refrences :1. Addiction to Indoor tanning; Mosher, C. , Burg, S. ; Archives of

Dermatology, vol. 146 No. 4, April 2010.

2. www.Wikipedia.com

3. http://health.howstuffworks.com/4. www.monkeysee.com

5. www.bytesizescience.com

6. Age, Rage and Wrinkles, Steve Hermann, GCI September 2007.

7. Formulating Effective Self-Tanners with DHA; Kurz, T., Merck, E.; Cosmetics & Toiletries® magazine,Vol. 109, No. 11, P. 55, 1994.

8. Laden, K., Zielinski, R.;J. Soc. Cosmetic Chemists,16,777-782 (1965).

THANK YOU!!!!

We dance round in a ring and suppose, but the Secret sits in the middle and knows.

Robert Frost