Methylene Blue

Methylene blue is a colorful organic chloride salt compound used in medicine and by biologists as a dye to help them see under the microscope. It is also known as Methylthioninium chloride or Swiss blue. It is represented by the formula \[C_{16}H_{18}CIN_{3}S\]. It was discovered in the year 1876 by German chemist Heinrich Caro.  Historically, it has been widely used in Africa for treating malaria, but now it has been disapproved when chloroquine and other drugs entered the market. Its molecular weight is 319.85 g/mol. It can cause damage to RBCs and also decreases the ability of the blood to carry oxygen which is the primary health concern of humans when exposed to methylene blue via oral or intravenous means. Methylene blue is a thiazine dye that is basic in nature. Methylene blue stains negatively charged cell components like nucleic acids. 

Structure of Methylene Blue

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Structure of Methylene Blue\[C_{16}H_{18}CIN_{3}S\]

Formula of Methylene Blue

Methylene blue is represented by the formula \[C_{16}H_{18}CIN_{3}S\]. It has  3,7-bis(dimethylamino) phenothiazine - 5 - ium as the counterion. Its IUPAC name is

7−(dimethylamino)phenothiazin−3−ylidene

7−(dimethylamino)phenothiazin−3−ylidene - methyl azanium; chloride. 

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Preparation of Methylene Blue

1. Methylene blue is prepared by the oxidation of dimethyl-4-phenylenediamine in the presence of sodium thiosulfate. 

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2. By treating the solution of N, N-dimethyl-p-phenylenediamine and N, N, -dimethylaniline hydrochlorides with \[H_{2}S\] and \[FeCl_{3}\] or another suitable oxidizing agent.

3. By oxidation of p- amino dimethyl aniline with ferric chloride in the presence of hydrogen sulphide. The dye is zinc chloride double salt of the chloride.

4. N, N-Dimethyl - p - phenylenediamine reacts with sodium thiosulfate to produce thiosulfuric acid which then condenses with N, N-dimethylaniline when it comes in the presence of \[Na_{2}Cr_{2}O_{7}\] or sodium dichromate to form the indamine, then with copper sulphate and sodium dichromate to the methylene blue.

Related Compounds to Methylene Blue

• Methylene Blue cation

• Azure A

• Azure B

• Methylene green

• 3-(Dimethylamino)-7-(methylamino)phenothiazin-5-ium

• 3,7-Bis(dimethylamino)-4-nitro phenothiazine-5-ium

Properties of Methylene Blue

• Methylene blue is deep blue in colour. 

• Methylene blue exhibits antioxidant properties.

• It also exhibits the property of antidepressants.

• It is highly soluble in water, chloroform, ethanol, and glacial acetic acid.

• It is insoluble in ethyl ether, xylene, and oleic acid.

• It also has the property of being antimalarial.

• It gets decomposed while heating and emits toxic fumes of nitrogen oxides, sulphur oxides, and chlorides. 

• It is non-carcinogenic in nature.

• It is slightly soluble in pyridine. 

• It is basic in nature. It's a basic thiazine dye. 

• It also exhibits cardioprotective properties. 

• It is non-combustible in nature.

• It acts as the enzyme inhibitor. 

What is the Role of Methylene Blue in the Field of Chemistry?

Methylene blue is widely used in the field of chemistry as a redox indicator in analytical chemistry, that is, to detect the presence or absence of oxygen and other oxidising agents due to the change in colour of the solution to blue when an electron is taken from methylene blue. Also, methylene blue is further used in the analysis of volumetric titrations and in Fehling’s test.

What is the Role of Methylene Blue in the Field of Biology?

Apart from chemistry, methylene blue is also used by biologists in various biological experiments as a stain, for example, for identification and visualisation of bacteria, for identification of nucleic acids, that is, DNA and RNA, or in the techniques of northern blotting or as an alternative to crystal violet chemical and ethidium bromide used in the technique of western blotting. Apart from this, methylene blue is also used to calculate the percentage of viable cells in a yeast sample.

What is the Role of Methylene Blue in the Field of Aquaculture?

The use of methylene blue is not restricted to the only chemical and medicinal field but has also been proved to be very useful in the field of aquaculture for the prevention of bacterial and fungal infections on the eggs of freshwater fish. It also increases the oxygen-carrying capacity of fish’s hemoglobin or for the treatment of fish infected with parasitic protozoan.

Uses of Methylene Blue

• Methylene blue is used in aqua farming for treating fungal infections.

• It is used as an antiseptic in cases of urinary tract infections. 

• It is also used as an indicator during the different chemical reactions.

• It is also used for the treatment of Methemoglobinemia.

• It is also used to dye paper and office supplies, but also to tone up silk colours.

• It is also used in the treatment of septic shock and anaphylaxis.

• It is also used as a dye for a number of staining procedures.

• It is also used as a temporary hair colorant.

• It is used as an oxidation-reduction agent in different chemical reactions.

• It is used in the treatment of pediatric and adult patients with methemoglobinemia.

• It is used as a reagent in oxidation-reduction titrations in volumetric analysis. 

• It is used in the treatment of hypoxia.

• It is used for dyeing cotton and wool. 

• Earlier methylene blue was used to check whether the pasteurized milk is bacteria-free or not. If the colour remains blue, that means milk is pasteurized properly, or else if blue colour disappears that means bacteria is consuming oxygen and the milk is not pasteurized properly.

What are the Warnings Associated with Methylene Blue when it is Used as a Component of a Drug?

Though methylene blue is widely used as a drug, there are certain risk factors associated with its use, due to which there are certain warning labels associated with it. The injections of methylene blue in combination with serotonergic drugs can lead to the serious serotonergic syndrome. Large doses of methylene blue can lead to vomiting, nausea, abdominal pain, dizziness, precordial pain, profuse sweating, headache, hypertension, dyspnea, urinary tract irritation, and mental confusion. It may also lead to the formation of methemoglobin ultimately causing cyanosis. Young infants and patients that have a deficiency of glucose-6-phosphate dehydrogenase can cause hemolytic anemia and hemolysis. Hypersensitivity reactions including generalized urticaria, anaphylaxis, tachycardia, hypotension, and bronchospasm have been reported at the site of injection.

What are the Trade Names of Methylene Blue?

Methylene blue is traded in the market with a variety of names like desmoid Piller, Pantone, desmoid pillen, vitableu, and urolene blue. Methylene blue has many synonym names as well like methylthionine chloride, tetra methylthionine chloride, methylthioninium chloride, Aizen methylene blue, and swiss blue. 

Fun Facts

• It is slightly irritant to the eyes.

• It can cause redness in the eyes tissues if it gets in contact with the eyes.

• If you are having a deficiency of glucose-6-phosphate dehydrogenase, then you should not be treated with methylene blue.

• Symptoms of overdose of Methylene blue are Abdominal or stomach pain, bigger, dilated, or enlarged pupils, dark urine, difficulty breathing, fever, headache, increased sensitivity of the eyes to light, nausea, pale skin, blue staining of the urine, skin, and mucous membranes, rapid heart rate, rapid shallow breathing, etc.