STEROID

STEROID

A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol andtestosterone, and the anti-inflammatory drug dexamethasone. The core of steroids is composed of twenty carbon atoms bonded together that take the form of four fused rings: three cyclohexane rings (designated as rings A, B, and C in the figure to the right) and one cyclopentane ring (the D ring). The steroids vary by the functional groups attached to this four-ring core and by the oxidation state of the rings. Sterols are special forms of steroids, with a hydroxyl group at position-3 and a skeleton derived from cholestane.

Hundreds of distinct steroids are found in plants, animals, and fungi. All steroids are made in cells either from the sterolslanosterol (animals and fungi) or from cycloartenol (plants). Both lanosterol and cycloartenol are derived from the cyclization of the triterpene squalene.

Figure 14:51. Steroid structure and numbering

Cholesterol is the most steroid in the human body.

Cholesterol has a basic structure of a steroid nucleus containing a methyl group, a hydroxy group attached to the ring first, and the alkyl chain.

The content of cholesterol in the blood ranges from 200-220 mg / dL, increased levels of cholesterol in the blood can constrict blood vessels in the heart, leading to coronary heart problems. Treatment is often done as the blood vessels dilate, installing rings or surgery.

Cholesterol in the body is formed in the liver from food. The structure of cholesterol can be seen in Figure 14:52.

Some of the common categories of steroids:

§  Animal

§  Insect

§  Ecdysteroids such as ecdysterone

§  Vertebrate

§  Steroid hormones

§  Sex steroids are a subset of sex hormones that produce sex differences or support reproduction. They include androgens, estrogens, and progestagens.

§  Corticosteroids include glucocorticoids and mineralocorticoids. Glucocorticoids regulate many aspects of metabolism and immune function, whereas mineralocorticoids help maintain blood volume and control renal excretion of electrolytes. Most medical 'steroid' drugs are corticosteroids.

§  Anabolic steroids are a class of steroids that interact with androgen receptors to increase muscle and bone synthesis. There are natural and synthetic anabolic steroids. In popular language, the word "steroids" usually refers to anabolic steroids.

§  Cholesterol, which modulates the fluidity of cell membranes and is the principal constituent of the plaques implicated in atherosclerosis.

§  Plant

§  Phytosterols

§  Brassinosteroids

§  Fungus

§  Ergosterols

Structural

It is also possible to classify steroids based upon their chemical composition. One example of how MeSH performs this classification is available at the Wikipedia MeSH catalog. Examples from this classification include:

Class	Examples	Number of carbon atoms
Cholestanes	cholesterol	27
Cholanes	cholic acid	24
Pregnanes	progesterone	21
Androstanes	testosterone	19
Estranes	estradiol	18

Gonane (or steroid nucleus) is the parent (17-carbon tetracyclic) hydrocarbon molecule without any alkyl sidechains