Ergosterol is a sterol
Sterols, also known as steroid alcohols, are a subgroup of the steroids and an important class of organic molecules. They occur naturally in plants, animals, and fungi, with the most familiar type of animal sterol being cholesterol...

 found in fungi, and named for ergot
Ergot or ergot fungi refers to a group of fungi of the genus Claviceps. The most prominent member of this group is Claviceps purpurea. This fungus grows on rye and related plants, and produces alkaloids that can cause ergotism in humans and other mammals who consume grains contaminated with its...

, a common name for the members of the fungal genus Claviceps from which ergosterol was first isolated. Ergosterol does not occur in plant or animal cells. It is a component of yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

 and fungal
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...

 cell 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...

s, serving the same function that cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...

 serves in animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....


Vitamin D2 precursor

Ergosterol is a biological precursor (a provitamin
A provitamin is a substance that may be converted within the body to a vitamin.The term "previtamin" is a synonym.For example, Provitamin B5 is a name for Panthenol, which may be converted in the body to Pantothenic Acid ....

) to vitamin D2
Vitamin D
Vitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....

. It is turned into viosterol by 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, and is then converted into ergocalciferol
Ergocalciferol is a form of vitamin D, also called vitamin D2. It is marketed under various names including Deltalin , Drisdol and Calcidol...

, a form of vitamin D also known as D2 or D2. For this reason, when yeast (such as brewer's yeast) and fungi (such as mushrooms), are exposed to ultraviolet light, significant amounts of vitamin D2 are produced.

Such vitamin D2 serves as the only available dietary supplement of vitamin D for vegans, who avoid dietary intake of any animal product. A related indirect process of producing vitamin D from fungi (though not one that is acceptable to vegans) also occurs, when milk-cows are fed diets of UV-irradiated-yeast (producing D2 from the ergosterol in the yeast) which eventually was excreted as D2 in cow milk. (However, this process was never as common as "supplementing" milk directly by adding vitamin D, or in earlier Steenbock process
Harry Steenbock
Harry Steenbock was a Professor of Biochemistry at the University of Wisconsin–Madison.-Vitamin D:...

, in which milk was exposed directly to ultraviolet light which converts milk's natural 7-dehydrocholesterol
7-Dehydrocholesterol is a zoosterol that functions in the serum as a cholesterol precursor, and is converted to vitamin D3 in the skin, therefore functioning as provitamin-D3. The presence of this compound in human skin enables humans to manufacture vitamin D3 from ultra-violet rays in the sun...

 content to vitamin D3).

Target for antifungal drugs

Because ergosterol is present in cell membranes of fungi yet absent in those of animals, it is a useful target for antifungal drug
Antifungal drug
An antifungal medication is a medication used to treat fungal infections such as athlete's foot, ringworm, candidiasis , serious systemic infections such as cryptococcal meningitis, and others...

s. Ergosterol is also present in the cell membranes of some protists, such as trypanosomes. This is the basis for the use of some antifungals against West African sleeping sickness.

Amphotericin B
Amphotericin B
Amphotericin B is a polyene antifungal drug, often used intravenously for systemic fungal infections...

 is an antifungal drug that targets ergosterol. It binds physically to ergosterol within the membrane, and, thus, creates a polar pore in fungal membranes. This causes ions (predominantly potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 and protons) and other molecules to leak out, which will kill the cell. Amphotericin B has been replaced by safer agents in most circumstances but is still used, despite its side-effects, for life-threatening fungal or protozoan infections.

Miconazole is an imidazole antifungal agent, developed by Janssen Pharmaceutica, commonly applied topically to the skin or to mucus membranes to cure fungal infections. It works by inhibiting the synthesis of ergosterol, a critical component of fungal cell membranes...

, itraconazole
Itraconazole , invented in 1984, is a triazole antifungal agent that is prescribed to patients with fungal infections. The drug may be given orally or intravenously.-Medical uses:...

, and clotrimazole
Clotrimazole is an antifungal medication commonly used in the treatment of fungal infections such as vaginal yeast infections, oral thrush, and ringworm...

 work in a different way, inhibiting synthesis of ergosterol from lanosterol. Ergosterol is a smaller molecule than lanosterol; it is synthesized by combining two molecules of farnesyl pyrophosphate, a 15-carbon-long terpenoid, into lanosterol, which has 30 carbons. Then, two methyl groups are removed, making ergosterol. The "azole" class of anti-fungal agents inhibit the enzyme that performs these demethylation steps in the biosynthetic pathway between lanosterol and ergosterol.

Other uses

Ergosterol is also used as an indicator of fungal biomass in soil. Though ergosterol does degrade over time, if kept below freezing in a dark environment, this degradation can be slowed or even stopped completely.

Research has shown ergosterol may have anti-tumor properties.


Ergosterol powder is an irritant to skin, eyes, and the respiratory tract. Ingestion of large amounts can cause hypercalcemia, which (if prolonged) can lead to calcium salt deposits in the soft tissues and, in particular, the kidneys.

External links

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