Protoveratrines-obtained from the rhizome of Veratrum album (American Hellebore)

B.1.1 Protoveratrines

Biological Sources It is obtained from the rhizome of Veratrum album L. (Liliaceae) and Veratrum viride Ait. (Liliaceae) (American Hellebore).

However, the alkaloids present in the rhizomes of V. viride are placed in three groups, such as:

Group-‘A’: Alkamines (esters of the steroidal bases) with organic acids, including germidine, germitrine, most valued therapeutically; besides, cevadine, neogermitrine, neoprotoveratrine, protoveratrines and veratridine,

Group-‘B’: (Glycosides of the alkamines), mainly pseudojervine and veratrosine, and

Group-‘C’: (Alkamines), germine, jervine, rubijervine, and veratramine.

Chemical Structure

Isolation Protoveratrine A and B are usually extracted together and referred to as ‘protoveratrines’. About 2 kg of dried rhizomes of V. album is powdered and then extracted with benzene and ammonia. The total alkaloids are purified by extraction with acetic acid, re-extracted into benzene. The solvent is removed under vacuum, the residue is dissolved in ether from which the crystalline powder of the crude protoveratrines separates out. The crude product is recrystallized from alcohol-acetic acid and upon subsequent alkalinization of the solution with dilute ammonia. By this method one may obtain 8-10 g of protoveratrine powder from 8 kg of V. album rhizomes. Consequently, protaverine A and B may be separated by the help of counter current distribution of the “protaverine” between benzene and acetate buffer (pH 5.5) and ultimately subjected to column chromatography on acid aaluminium oxide (Al₂O₃).

Characteristic Features The characteristic features of the protoveratrines are as follows:

(i) The sternutative crystals obtained from ethanol have a slightly bitter taste.

(ii) It decomposes at 266-267°C.

(iii) Its specific rotation [α]_D²⁵ -38.6^o (pyridine), and [α]_D²⁵-85^o (C = 1.99 in chloroform).

(iv) It is soluble in chloroform, dilute aqueous acidic solutions and slightly soluble in ether. It is practically insoluble in water and petroleum ether.

However, the characteristic features of protoveratrine A and B are as stated below:

Uses

1. It is used as an antihypertensive agent which exerts its action through reflex inhibition of pressor

receptors in the heart and carotid sinus.

2. It also possesses emetic action.

3. It is used in the treatment of toxemia of pregnancy.

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* Blount, J. Chem. Soc, 122, (1935); Vejdelek et. al. Chem. Listy 153, 33, (1956); Coll. Czech. Chem. Commun., 22, 98 (1957).
Source:Pharmacognosy And Pharmacobiotechnology By Ashutosh Kar