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Zinc pyrithione

Zinc pyrithione

Overview
Zinc pyrithione is a coordination complex of zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

. This colourless solid is used as an antifungal and antibacterial agent. This coordination complex, which has many names, was first reported in the 1930s.

The pyrithione ligands, which are formally monoanions, are chelated
Chelation
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....

 to Zn2+ via oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 centers. In the crystalline state, zinc pyrithione exists as a centrosymmetric dimer (see figure).
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Encyclopedia
Zinc pyrithione is a coordination complex of zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

. This colourless solid is used as an antifungal and antibacterial agent. This coordination complex, which has many names, was first reported in the 1930s.

Structure of the compound


The pyrithione ligands, which are formally monoanions, are chelated
Chelation
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....

 to Zn2+ via oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 centers. In the crystalline state, zinc pyrithione exists as a centrosymmetric dimer (see figure). Each zinc is bonded to two sulfur and three oxygen centers. In solution, however, the dimers dissociate via scission of one Zn-O bond.

Pyrithione is the conjugate base derived from 2-mercaptopyridine-N-oxide (CAS# 1121-31-9), a derivative of pyridine-N-oxide
Pyridine-N-oxide
Pyridine-N-oxide is the heterocyclic compound with the formula C5H5NO. This colourless, hygroscopic solid is the product of the oxidation of pyridine. It was originally prepared using peracids as the oxidising agent. The molecule is planar. The compound is used infrequently as an oxidizing...

.

Medical


Zinc pyrithione is best known for its use in treating dandruff
Dandruff
Dandruff is the shedding of dead skin cells from the scalp . Dandruff is sometimes caused by frequent exposure to extreme heat and cold. As it is normal for skin cells to die and flake off, a small amount of flaking is normal and common; about 487,000 cells/cm2 get released normally after...

 and seborrhoeic dermatitis
Seborrhoeic dermatitis
Seborrhoeic dermatitis is an inflammatory skin disorder affecting the scalp, face, and torso. Typically, seborrheic dermatitis presents with scaly, flaky, itchy, and red skin. It particularly affects the sebaceous-gland-rich areas of skin...

. It also has antibacterial properties and is effective against many pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

s from the streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...

 and staphylococcus
Staphylococcus
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....

 class. Its other medical applications include treatments of psoriasis
Psoriasis
Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...

, eczema
Eczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...

, ringworm, fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

, athletes foot, dry skin, atopic dermatitis
Atopic dermatitis
Atopic dermatitis is an inflammatory, chronically relapsing, non-contagious and pruritic skin disorder...

, tinea
Tinea
Tinea is a general term used to describe skin mycoses. The term ringworm is even less precise, but is usually considered a synonym.It is sometimes equated with dermatophytosis, and it is true that most conditions identified as "tinea" are members of the imperfect fungi that make up the dermatophytes...

, and vitiligo
Vitiligo
Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes, the cells responsible for skin pigmentation, die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress,...

.

Zinc pyrithione is approved for over-the-counter topical use in the United States as a treatment for dandruff
Dandruff
Dandruff is the shedding of dead skin cells from the scalp . Dandruff is sometimes caused by frequent exposure to extreme heat and cold. As it is normal for skin cells to die and flake off, a small amount of flaking is normal and common; about 487,000 cells/cm2 get released normally after...

. It is the active ingredient in several anti-dandruff shampoos such as Head & Shoulders
Head & Shoulders
Head & Shoulders is a brand of anti-dandruff shampoo produced by Procter & Gamble. Head & Shoulders Classic Clean Shampoo is the top-selling shampoo in the United States by dollar sales.- History :...

. However, in its industrial forms and strengths, it may be harmful by contact or ingestion.

In paint


Due to its low solubility
Solubility
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...

 in water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 (8 ppm at neutral pH), zinc pyrithione is suitable for use in outdoor paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

s and other products that provide protection against mildew
Mildew
Mildew refers to certain kinds of molds or fungi.In Old English, it meant honeydew , and later came to mean mildew in the modern sense of mold or fungus....

 and algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

. It is an effective algaecide
Algaecide
An algaecide or algicide is a substance used for killing and preventing the growth of algae.-Natural algicides:Barley straw, in England, is placed in mesh bags and floated in fish ponds or water gardens to help reduce algal growth without harming pond plants and animals...

. It is chemically incompatible with paints relying on metal carboxylate curing agents. When used in latex paints with water containing high amount of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

, a sequestering agent that will preferentially bind the iron ions is needed. Its decomposition by ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 light is slow, providing years of protection even against direct sunlight.

In sponges


Zinc pyrithione is also used as an antibacterial treatment for household sponges, most notably by the 3M Corporation.

Mechanism of action


Its antifungal effect is proposed to derive from its ability to disrupt membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...

 transport by blocking the proton pump
Proton pump
A proton pump is an integral membrane protein that is capable of moving protons across a cell membrane, mitochondrion, or other organelle. Mechanisms are based on conformational changes of the protein structure or on the Q cycle.-Function:...

 that energizes the transport mechanism. A new study proposes that the mode of action of zinc pyrithione arises from iron starvation of the substrate. Experiments have suggested that fungi are capable of inactivating pyrithione in low concentrations.

Possible health concerns



Recent research suggests that zinc pyrithione is a potent heat shock
Heat shock
In biochemistry, heat shock is the effect of subjecting a cell to a higher temperature than that of the ideal body temperature of the organism from which the cell line was derived.-Heat shock response:...

 response inducer that may cause DNA damage and PARP-dependent energy crisis in cultured human keratinocytes and melanocytes, in concentrations as low as nanomoles.

See also

  • selenium disulfide, an active ingredient used in shampoos such as Selsun Blue
    Selsun Blue
    Selsun Blue is an over-the-counter brand of dandruff shampoo now owned by Sanofi-Aventis. First made by Abbott Laboratories, the brand was bought in Chattem in 2002. Chattem was acquired by Sanofi-Aventis in 2010. Selsun Blue has been marketed as a more effective alternative to brand leader Head &...

    .
  • Ketoconazole
    Ketoconazole
    Ketoconazole is a synthetic antifungal drug used to prevent and treat fungal skin infections, especially in immunocompromised patients such as those with AIDS or those on chemotherapy. Ketoconazole is sold commercially as an anti-dandruff shampoo, topical cream, and oral tablet.Ketoconazole is...

    , another antifungal agent used in shampoos.

External links