Page 113 - Medicinal Plants_PharmD general

+ III. Lipids

These are fats and fat-like substances that are insoluble in water, but
soluble in organic solvents .They include fixed oils, fats, waxes, sterols and
phosphatides (glycerides of fatty acids and phosphoric acid with nitrogen
linkage).

Fixed oils and fats are mixture of esters of fatty acids with trihydric
alcohol (glycerol) and usually called glycerides.

CH2OH Fatty acids CH2OCOR 1

CHOH + CHOCOR
2
CH2OH
CH2OCOR3
Glycerol Glyceride

Fixed oils and fats often occur in seeds where they may replace the
carbohydrates as a reserve food material. They are greasy and non-volatile
at ordinary temperature.

Fixed oils are viscous liquid at ordinary temperature. Fats are
semisolid e.g. lard or solid e.g. Cacao butter. Their consistency depend on
the proportion of the saturated glycerides (solid) and unsaturated glycerides
(fluidy). Fats are rich in solid glycerides while oils are rich in liquid
glycerides.

Properties of Oil and Fats:

Fats and oils are lighter than and insoluble in water, leave permanent
stains on paper, soluble in ether, chloroform and benzene. They are
hydrolysed by aqueous alkalies giving soap and glycerol.

-113-