32? PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Phytosterols. C 27 H 46 O. 



Compounds very similar to cholesterol have been prepared from plants 

 and have been termed phytosterols. They are probably mixtures of isomeric 

 compounds, that from the Calabar bean having been shown to be a mixture of 

 sitosterol, C 27 H 45 OH, and stigmasterol, C 30 H 47 OH. They are mostly contained 

 in the fat of plant seeds. 



They are prepared from the vegetable fat of the seeds by saponification 

 with alcoholic potash ; the alcohol is evaporated and the residue dissolved 

 in water. The aqueous solution is extracted with ether, and this extract 

 on evaporation yields the phytosterol, which is recrystallised from alcohol. 



The phytosterols crystallise like cholesterol, but the crystals are usually 

 six-sided. The melting-point of the phytosterols varies from 135-144, 

 but is usually 135-137. In solubility they resemble cholesterol and form 

 acetates and benzoates. The acetates melt at 125-137. They can only be 

 distinguished from cholesterol by their crystalline form and the melting-point 

 of the acetates. 



BILE ACIDS. 



The bile of animals contains the sodium salts of glycocholic and 

 taurocholic acids, glycocholeic and taurocholeic acids. These acids 

 are decomposed by boiling the bile with sodium hydroxide and yield 

 glycine or taurine and cholalic, choleic and deoxycholic acids. 

 Choleic acid, according to Wieland and Sorge, 1 is a combination of 

 8 mols. of deoxycholeic acid with I mol. of fatty acid (palmitic or 

 stearic). They have prepared similar combinations of deoxycholeic 

 acid with acetic and other fatty acids. 



Cholalic Acid or Cholic Acid. C 24 H 40 O 5 . 



JOOH Though the constitution of cholalic acid is 



CHOH unknown, its properties and reactions seem to 

 CH 2 OH show that it should be included amongst the 

 hydro-aromatic compounds. Its products of oxi- 

 dation and their properties show that it is a trihydroxy monobasic acid. 

 Dehydrocholalic Acid. C2 4 H 34 O 5 . 



)OH This acid is obtained by the oxidation of cholalic 



'CO acic ^ w ^k chromic acid in glacial acetic acid. It crys- 



tallises from alcohol in needles melting at 231-232; it 

 \. ^"^ is soluble with difficulty in cold water and cold alcohol, 

 is dextrorotatory and has a bitter taste. It forms esters, 



yields a trioxime with hydroxylamine and contains i keto and 2 aldehyde 

 groups. 



Bilianic Acid, C2 4 H 34 O 8 , and Isobilianic Acid. 



^COOH These acids are formed by the oxidation of cholalic 



/^ COOH acid or dehydrocholalic acid with potassium perman- 

 ^19-^-n -^. coOH ganate in alkaline solution. 



Bilianic acid is soluble with difficulty in cold water, 

 and crystallises from alcohol in sparkling crystals. It is 

 a tribasic acid containing two ketonic groups. 



CO 



'CO 



Cilianic Acid. C 2 oH 28 O 8 . 



This is another tribasic acid obtained by the oxidation of cholalic acid. 

 1 Zeitschr. physiol. Chem., 1916, 97, i. 



