steroid :-
introduction :- Steroids constitute a group of structural related organic compounds that are widely distributed both in plants and animals kingdom
Basically steroids are the natural products which are extracted from the nature and can also be synthesised in laboratory .
Steroids have 1,2-cyclopentenophenanthrene nuclei in their structure
steroid include compounds with wide variation in the structure and and encomposed a variety of components of vital importance to life such as cholesterol, bile acids, vitamin D, sex hormones and antibiotic etc.
Any compound which gives Diel's hydrocarbon with Se distillation is defined as steroid.
Diel's hydrocarbon:- Diel's hydrocarbon is a solid with melting point 126 to 127 degree Celsius
its molecular formula is C18H26
it was first obtained when steroids are distillated with Se.
when steroids are distillated at 420 degree Celsius yields, mainly two hydrocarbons crysene and little picene.
structure of Diel's hydrocarbon was confirmed by its synthesis, starting from 2-(1-nephthyl)-ethyl magnesium bromide and 2,5 dimethyl cyclopentanone.
Sterols:- sterols are known as steroid alcohol , are a sub group of the steroids and an important class of organic molecules. steroids occur in animals and plant oil and fat .
They are crystalline compounds, and contain an alcoholic group they occur free or as ester of higher fatty acids and isolated from unsaponificable portion of oil and fat.
Classification of on the basis of source:-
three types
1. 200 sterols ( animal source )[ cholesterol, cholestanol, Coprosterol]
2. phytosterols ( plant source)[Campesterol, sitosterol, stigmasterol]
3. Mycosterols( yeast and fungi source)[Ergosterol, vitamin D]
Structure (nucleus and number)
Gonane also known as steran or cyclopentanoperhydrophenanthrene, the simplest steroid and the nuclear of all steroids and sterols, is composed of C17 atoms in C-C bond forming and four fused ring in a three dimensional shape
the three cyclohexane ring A B and C forms the skeleton of perhydroderivative of phenanthrene.
The D ring has cyclopentane structure .
When the 2 methyl groups and B,C side chains (at C17) are present, the steroids are said to have cholestane frameworks sterols are forms of steroids with a hydroxyl group at position 3 and a skeletal derived from cholestane .
All the steroids have this basic nucleus they very in the functional group attached and the side chain attached to these four rings.
cholesterol :-
molecular formula of cholesterol is C27H46O and its melting point is 149 degree Celsius
this is the sterol of higher animals occurring free or as fatty esters in all animal cells, particularly in the brain and spinal cord. cholesterol was first isolated from human ga stone.
the main sources of cholesterol are the fish liver oil, the spinal cord of cattles .
cholesterol is a white crystalline solid which is optically active .
cholesterol is a waxy substance found normally in blood predominantly produced in liver but alsl found in food such as red meat, high fat cheese , butter eggs etc.
cholesterol is essential for maintaining the good heart but to high concentration of cholesterol in the blood can leads to high blood pressure, heart disease etc. but good and healthy lifestyle can help to lower cholesterol level and the significant to reduce the risk.
cholesterol travel in the blood transported in molecules called lipoprotein they are sphere shaped assemblies that keeps the cholesterol separated from the blood.
There are two types of lipoproteins:-
1. LDL(low density lipoprotein):;
It is a bad cholesterol if there is too much LDL in blood it can slowly built in the arteries making them narrower which increases of heart diseases.
2. high density lipoprotein (HDL):-
It is a good cholesterol
It helps to remove excess cholesterol from the bloodstream and return it to the liver where it is broken down and passed out of the body.
the structure of cholesterol was elucidated only after a tremendous amount of work particularly by wielard, windairs and their co-workers (1903-1932)
structure determination :-
for the elucidation of cholesterol , firstly it is important to know the structure of cholesterol
the molecule consists of a side chain and a nucleus composed of four rings .
these rings are usually designed A,B,C and D
it also contains two methyl group at C-10 and C-30
THE STRUCTURE ELLUSIDATION OF CHOLESTEROL CAN BE DIVIDED INTO FOUR PARTS
1 STRUCTURE OF THE RING SYSTEM
2 POSITION OF HYDROXYL GROUP AND DOUBLE BOND
3 NATURE AND POSITION OF SIDE CHAIN
4 POSITION OF 2 ANGULAR METHYL GROUPS
Structure of the ring system molecular:- Molecular formula of cholesterol is C27H46O
on acetylation, cholesterol forms monoacetal and this reaction confirms the present of a hydroxy group
choesterol is treated with H2 in the presence of catalyst and with bromine(Br2) it absorbs one mole of H2 and 1 mole of Br2 which indicates the presence of 1 double bond
Cholesterol shows the following set of reactions:-
This leads to the following conclusion:-
1 to 2 prove the presence of 1 double bond
2 to 3 (a ketone) shows that cholesterol is secondary alcohol
3 to 4 cholestane is a saturated hydrocarbon and corresponds to the general formula CnH2n - 6 and hence cholesterol is a tetracyclic compound
the ring in the steroid nucleus were opened to give a dicarboxylic acid and the relative positions of the two carboxylic groups with respect to each other were determined by the application of blanc's rule :- which states that on heating with acetic anhydride, 1,5 dicarboxylic acids form cyclic anhydride and 1,6 - dicarboxylic acids form cyclopentanones with eliminatiom of CO2.
