ALIZARIN: CHARACTERISTICS, PREPARATION, USES AND TOXICITY - BIOLOGY - 2025

The alizarin is a set of organic dyes which are obtained naturally from the roots of a plant blonde name, discovered by French chemist Pierre-Jean in 1826.

The first dye synthesized was alizarin red, but there is also alizarin yellow, alizarin blue and alizarin violet. Of all those mentioned, alizarin red is the one with the greatest applications, and as it is the most widely used we usually refer to it simply as alizarin.

Chemical structure of alizarin and 3D structure of alizarin. Source: Arrowsmaster / Ben Mills and Jynto

Alizarin red was the first to be artificially (synthetically) synthesized from anthracene, thanks to the discovery of two German chemists, Carl Graebe and Carl Liebermann, in 1868. The scientific name for alizarin red is 1,2-dihydroxyanthraquinone, and Its chemical formula is C14H8O4.

The use of the pigment from the blonde root to dye fabrics dates back to the time of Pharaoh Tutankhamen, as evidenced by finds in his tomb. Likewise, it was also observed in the ruins of Pompeii.

Later, in the time of Charlemagne, the cultivation of the blonde was promoted, becoming an important economic exercise in the region.

For a long time it was used to dye the fabrics with which they made the uniforms of soldiers who belonged to the English and British army. The uniforms had a very particular red color that characterized them; being called by the popular slang Redcoats.

characteristics

Alizarin was an essential compound in the manufacture of different dyes or pigments, coming from the Rubia, generally known as "Rose madder" and "alizarin carmine." From these tinctures came the name of crimson red.

Today alizarin red is used as a stain for the determination of various studies involving calcium. It is a powder formed by small crystals of orange-reddish or orange-purple color. It is also known by the name of red alizarin. Its molecular mass is 240.21 g / mol, and its melting point is 277-278 ° C.

The natural form is obtained from the roots of the blonde, specifically from the species R. tinctorum and R. cordifolia.

Subsequently, the production of natural pigment from the root of the blonde was replaced by the synthetic production from anthracene. This process requires the oxidation of anthraquinone-2-sulfonic acid with sodium nitrate in a concentrated solution of sodium hydroxide (NaOH).

After the 1958 years, the use of red alizarin was replaced by other pigments with greater stability to light. Examples are the quinacridone derivatives developed by Dupont.

Variants of alizarin (alizarin dyes)

All variants have an anthraquinone nucleus in common.

Alizarin Carmine

Alizarin carmine is derived from the precipitate of alizarin, a lacquer-type pigment that provides good permanence on substrates and is semi-dark red in color.

Alizarin yellow

There is a variant called alizarin yellow R used as a pH indicator. This substance below 10.2 is yellow, but above 12 it is red.

Alizarin blue

For its part, alizarin blue is a pH indicator that has two turning zones: one at pH between 0.0-1.6, where it turns from pink to yellow, and another turning interval between pH 6.0-7.6, whose change is from yellow to green.

Alizarin Violet

It is a colorant used for the spectrophotometric determination of aluminum in the presence of surfactant substances.

Preparation of the alizarin red solution

The preparation will depend on the utility that is going to give it. For example, in the evaluation techniques of the biomineralization process it is used at a concentration of 0.1%

For the marking of geniculated coralline algae, the concentration with the best results is 0.25%.

Applications

Although it is true that for years alizarin was used as a textile dye, today it has other applications. For example, at the health level it is useful to determine the presence of calcium in various forms.

In other areas such as geology, alizarin is useful for detecting certain minerals, such as calcium carbonate, aragonite, and calcite.

Most frequent uses

Currently it is widely used to reveal the presence of calcium deposits in the formation of bone tissue. One of the areas that alizarin red uses the most is histochemistry.

For example, it is used during the biomineralization process in in vitro cell cultures of the osteogenic line, where red alizarin stains the calcium crystals formed during the process.

Also in the diaphanization technique, a procedure that allows studying bone and dental development in experimental animals. Thanks to red alizarin, it is possible to identify the ossification centers.

On the other hand, it is useful to detect the presence of calcium phosphate crystals in synovial fluid.

Investigations that have used the dye alizarin

Vanegas et al. Used red alizarin to evaluate osteoblast development on titanium surfaces; Candidate material for the manufacture of dental implants. Thanks to this staining technique, he was able to observe that the osteoblasts managed to adhere, proliferate and biomineralize on the tested surfaces.

On the other hand, Rivera et al. Evaluated the age and growth rate of coralline algae in the South West of the Gulf of California, Mexico. The authors performed two types of marking. The first was using alizarin red and the second with metallic stainless wire markings. Alizarin marking was the best technique for this purpose.

Likewise, Aguilar P studied the validation of the potentiometric method by selective ion using alizarin for the determination of fluorine in salt, water and urine, turning out to be a satisfactory method.

Dantas et al. Used alizarin violet N (AVN) as a spectrophotometric reagent in the determination of aluminum, obtaining good results.

Toxicity

The NFPA (National Fire Protection Association) classifies alizarin red as follows:

- Health risk in grade 2 (moderate risk).

- Risk of flammability in grade 1 (slight risk).

- Reactivity risk in grade 0 (no risk).

References

1. Vanegas J, Garzón-Alvarado D, Casale M. Interaction between osteoblasts and titanium surfaces: application in dental implants. Rev Cubana Invest Bioméd. 2010; 29 (1). Available at: scielo.org
2. Rivera G, García A, Moreno F. Alizarin clearing technique for the study of bone development Colombian journal salud libre. 2015; 10 (2): 109-115. Available at: researchgate.
3. Aguilar P. Validation of the Ion Selective Potentiometric method for the determination of Fluorine in salt, water and urine. Peru. med. exp. public health. 2001; 18 (1-2): 21-23. Available at: scielo.org.pe/scielo
4. Alizarin carmine. Wikipedia, The Free Encyclopedia. 8 May 2017, 15:54 UTC. 30 May 2019, 00:19.
5. "Alizarin." Wikipedia, The Free Encyclopedia. 20 Feb 2019, 15:52 UTC. 30 May 2019, 00:21 en.wikipedia.org.
6. Dantas, Alailson Falcão, Costa, Antônio Celso Spínola, & Ferreira, Sérgio Luís Costa. Use of alizarin violet N (AVN) as a spectrophotometric reagent in the determination of aluminum. Chemistry Nova, 2000; 23 (2), 155-160. Available at: Scielo.org