2. Steroidal alkaloids Flashcards
What are steroidal alkaloids?
Steroidal Alkaloids are characterised by cyclopentanophenanthrene nucleus.
They apparently are either formed from cholesterol, or they have cholesterol ,a common precursor.
They arise by inclusion of a basic nitrogen at some point in steroid molecule.
What are important steroidal alkaloidal drugs?
The important drugs and their alkaloids of this group are veratrum viride & veratrum album.
What is veratrum viride?
Veratrum viride,American or green hellebore, consists of dried rhizome and roots of Veratrum viride Aiton(Fam. Liliaceae).
What is the classification of alkaloids of veratrum viride?
The classification of the alkaloids obtained from veratrum viride is based on chemical constitution into Group 1, 2 and 3 respectively.
What is group 1 comprised of?
Group 1: consists of esters of steroidal bases(alkamines)& with organic
acids include cevadine, germidine, veratridine etc.
What is group 2 comprised of?
Group 2: includes pseudojervine and veratrosine, which are glycosides of alkamines.
What is group 3 comprised of?
Group 3: Alkamines themselves — germine, jervine, veratramine compose this group.
The ester alkaloids, germidine and germitrine, are probably the most important therapeutically
What is Veratrum album?
Veratrum album ,European or white hellebore , consists of dried rhizome.
It is similar in appearance and structure to V. viride but external color is much lighter.
What is the composition of V. Album?
The drug contains a complex mixture of ester alkaloids, glycoalkaloids and alkamines similar and in some cases identical to those occurring in V.viride.
Two ester alkaloids, protoveratrine A & protoveratrine B are the most active.
What does V. album yield on hydrolysis?
On hydrolysis both yield protoverine, acetic acid, methylbutyric acid( in protoveratrine A) or methyldihydroxybutyric acid (in protoveratrine B).
What are the two steroidal alkaloids of these groups?
Numerous steroidal alkaloids are present in both V.album & V.viride
There are two distinct chemical groups of veratrum steroidal alkaloids and referred to as jerveratrum and ceveratrum groups.
What is Jeveratrum alkaloids?
Jerveratrum alkaloids ; occur in plants as free alkamines & also combined as glycosides with one molecule of D-glucose.
Examples:
Pseudojervine derived from jervine & veratrosine derived from veratramine.
What are ceveratrum alkaloids?
Ceveratrum alkaloids; highly hydroxylated compounds ,occur in plant esterified with two or more acids but are also found unconjugated.
It is the ester alkaloids that are responsible for hypotensive activity of veratrum.
Examples:
Esters of germine, protoverine and veracevine.
What is the collection and preparation of Veratrum?
Rhizome is dug up in autumn, often sliced longitudinally into halves or quarters to facilitate drying, and sometimes deprived of many of the roots.
What are the uses of Veratrum?
Both white and green hellebores are employed as insecticides.
American veratrum is used for preparation of Veriloid, a mixture of hypotensive alkaloids.
European veratrum is used for preparation of protoveratrines.
