Strophanthus-Strophanthus hispidus De*, or of Strophanthus kombe Oliver, belonging to the family Apocynaceae

2.3.4 Strophanthus

Synonyms Semino stropanthi.

Biological Source These are the dried and ripe seeds of Strophanthus hispidus De*, or of Strophanthus kombe Oliver, belonging to the family Apocynaceae, deprived of the awns.

Geographical Source Strophanthus plants are elimbers, which being perennial large & woody, found to be indigenous in the vicinity of Shire river, Nyanza and Tanganyika lakes of Eastern tropical Africa.

Preparation The ripe strophanthus fruit comprises of two fully developed follicles each about 30cm broad with tapering at both ends and consisting of a number of seeds. The ripe fruits are collected from the wild plants, the seeds are subsequently separated and freed from their awns.

Description

Colour : Greyish green to light yellowish brown

Odour : Slight unpleasant

Taste : Bitter

Size : Length 1- 2 cm; Breadth = 3-5 mm; Thickness = 2 mm

Shape : Lanceolate to linear-lanceolate, acute at the apex, rounded or blunt at the base

Weight : For 100 seeds 3-4 g

Specific : On treating with 80% H₂SO₄ the endosperm exhibits a deep feature Emerald green colour.

Chemical Constituents The seeds of strophanthus usually contain three vital glycosides, namely:

K-strophanthoside, K-strophanthride b and cymarin. Interestingly, all these glycosides undergo hydrolysis to yield strophanthidin.

The structure of strophanthidin and its allied glycosides are given below:

K-Strophanthoside It is the main constituent of S.kombe, the aglycone is known as strophanthidin that has the following characteristic features, namely:

(a) Three—OH moieties at positions C-3, C-5 and C-14.

(b) An aldehydic (—CHO) function is present at C-10 which being an essential requirement.

(c) At C-17 an unsaturated 5-membered lactone ring, and

(d) At C-3 an ‘O’ atom forms a bridge to the sugar compotent(s) essentially comprising of cymarose, β-D-glucose and α-D-glucose.

Acidic hydrolysis of K-strophanthoside gives rise to the aglycone strophanthidin along with a triose sugar known as strophanthotriose that comprise of one mole of cymarose and two moles of glucose. Enzymatic hydrolysis of K-strophanthoside using the enzymes-glucosidase, usually present in yeast, helps in cleaving off the terminal a-D glucose thereby yielding the secondary glycoside known as K-strophanthidin b. Further hydrolysis of the resulting product with strophanthobiase, the former yields the glycosides cymarin which comprises of the aglycone strophanthidin along with one mole each of cymarin and β-D-glucose.

However, it is worth noting that the acidic hydrolysis of K-strophanthoside gives rise to the aglycone strophanthidin and strophanthobiase which being a disaccharide (or biose) It may be observed that the terminal glucose possesses an alpha linkage, while the one attached to cymarose bears a beta linkage.

Chemical Tests

1. Generally, the strophanthus glycosides exhibit an emerald green colouration on the addition of sulphuric acid.

2. Dissolve about 0.1g of strophanthin in 5 ml of water and add to it a few drops of ferric chloride solution followed by a 1-2 ml of concentrated sulphuric acid; the appearance of an initial red precipitate that finally turns green within a period of 1-2 hours.

3. To 50 mg of strophanthin add 5 ml of water, shake and add 2 ml of 2% tannic acid solution, the appearance of a distinct precipitate affirms its presence.

4. It shows positive Baljet Test, Legal Test and Keller Killiani Test (see Section 2.3.1).

Uses

1. It is used intravenously for treating emergency cardiac conditions. However, orally strophanthin is not so active.

2. These glycosides have been found to exert less cumulative effect unlike the digitalis glycosides.

3. Overall their therapeutic actions are very much similar to those of Digitalis.

----------------------------

* De = De Candolle

Source: Pharmacognosy And Pharmacobiotechnology By Ashutosh Kar