In this article we will discuss about the groups and useful roles of steroids.
Groups of Steroids:
Some of the major groups of steroids are as follows:
1. Sterols:
Steroids with 8-10 carbon long aliphatic side chain at carbon 17 and at least one alcoholic hydroxyl (e.g., at position 3), e.g., cholesterol, ergasterol, coprosterol, stigmasterol, sitosterol, campesterol.
2. Bile Acids:
They are steroid carboxylic acids derived from cholesterol, e.g., glycocholic acid, taurocholic acid.
3. Gonadal (Sex) Hormones:
Estradiol (oestrogen), testosterone, progesterone.
4. Adrenocortical Hormones:
Corticosterone.
5. Cardiac Glycosides:
They contain carbohydrate steroid complex with steroid nucleus having unsaturated lactone ring attached to carbon 17 e.g., digitoxin (from Digitalis), strophanthin (from Strophanthus).
6. Saponins:
They are glycoside having steroids (e.g., sapogenin) which form foam when their watery solution is shaken. Saponins are widely distributed in plants (e.g., Saponaria, Quillaja). They can dissolve RBCs even in high dilution.
7. Anabolic Steroids:
They are synthetic derivatives of testosterone which are used clinically in promoting growth and repair of body tissues in senile and debilitating illness. Toad poisons and some carcinogenic hydrocarbons are also steroid in nature.
Cholesterol:
Cholesterol (C27H45OH) is the common sterol found in many animals, human beings and some plants (e.g., Potato or Solanum tuberosum). It is manufactured inside the body in liver as well as got from outside. Cholesterol occurs in both free (Fig. 9.14) and combined form when it is esterified with a fatty acid.
Cholesterol and its ester are insoluble in water. Therefore, when cholesterol level rises in blood, it tends to get deposited in the walls of arteries. This is known as atherosclerosis. It leads to high blood pressure and many heart diseases. Crystallization inside gall bladder leads to formation of gall bladder stones.
Useful Roles of Steroids:
Some of the roles of steroids are as follows:
(i) Cholesterol is precursor of most steroid hormones like progesterone, estradiol (female sex hormones), testosterone (male sex hormone), aldosterone, cortisol (adrenal cortex hormones), ecdysone (moulting hormone),
(ii) Steroid hormones control sex expression, sexual cycle, allergies, differentiation and body fluids,
(iii) Cholesterol forms vitamin D on exposure to ultraviolet rays,
(iv) Cholesterol is useful in absorption of fatty acids,
(v) Steroid diosgenin obtained from Dioscorea (yam) has antifertility properties,
(vi) Anabolic steroids are useful in correcting debilitating disorders. They are misused for body building by players,
(vii) Sterols are known to be essential for plant growth, induction of flowering and expression of sex in some plants,
(viii) Cholesterol is a constituent of animal cell membrane,
(ix) Cholesterol helps in forming bile salts,
(x) Cardiac glycosides tone up cardiac muscles and correct arrhythmia,
(xi) Birth control pills have steroid hormone progesterone with or without oestrogen.