Agriculture Reference
In-Depth Information
Another medicinally important member of the genus is Indian
S. glabra
(Roxb.) Mier, which is
employed in traditional Indian medicine for the treatment of asthma, dysentery, and fevers. Several
alkaloids isolated from this species have been investigated for various pharmacological activities,
including antitumor (cycleanine), bactericidal, anticholesterase (palmitine), and antispasmolytic
(pronuciferine) effects and hyperthermia in rats (tetrahydropalmitine hydrochloride).
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STROPHANTHUS SPECIES
Family —
Apocynaceae
The seeds of the major African
Strophanthus
species
S. kombe and S. gratus
Hook (Strauch)
yield very potent cardiac glycosides, thestrophantins. Similar glycosides are present in less well-
known species, such as
S. sarmentosus
D.C.,
S. hispidus
D.C., and
S. gracilis
Schum.
S. kombe
yields a mixture of glycosides collectively known as strophanthin K. The aglycone is
strophanthidin, and the principal glycosides are K-strophantoside, K-strophanthin-B, and cymarin.
S. gratus
produces a stable glycoside bearing a rhamnose moiety, g-strophanthin or ouabain. The
compound can be isolated in very pure crystalline form, and it is used as the biological standard
for the assay of other cardiac glycosides. Ouabain is active at relatively low doses, is very soluble in
water, and offers several pharmacokinetic advantages over digitalis glycosides for patients requir-
ing rapid digitalization. The effect is of shorter duration, and the drug is not cumulative. Ouabain is
badly absorbed when given orally and therefore is administered mostly as an injection. It does not
cause peripheral vasoconstriction as digitalis does.
519
S. hispidus
contains about 2% K-strophanthoside-a and about 8% of other cardiac glycosides,
including cymaroside, saponosides, and the amorphous strophanthin H.
S. sarmentosus
yields two main glycosides depending on the geographical locations where the
plant was collected. The genin in the glycosides of the plant found in Zaire, Togo, and southern
Nigeria is sarvogenin, while the plants that grow in the savanna belt of northern Nigeria and Mali
elaborate glycosides based on sarmentogenin. The sugars associated with these genins are known
as sarmentose and digitalose.
437,519,10 01
S gracilis
yields the largest quantities of total glycosides in
the mixture. The major compounds found in the plant include strophanthidin, strophanthidol, emi-
cymarin, odoroside H and G, and graciloside.
437,519
Pharmacological Properties of Strophanthidin and Its Congeners —
Strophanthus
glyco-
sides exhibit essentially the same therapeutic activity as the digitalis glycosides. The cardiovascular
activity of
Strophanthus
glycosides cannot be matched by those of digitalis. Strophanthins gener-
ally have extremely rapid onset of activity following an intravenous injection.
According to Weiss,
511
the effect on the pulse and easing of the dyspnea can be observed within
minutes, even while the slow intravenous injection is being administered. The drug has been found use-
ful in coronary insufficiency and its attendant angina. The possibility of strophanthin-induced coronary
infarction is a contraindication in the use of strophanthin as the initial drug for this purpose, except
when muscular insufficiency has been clearly established.
511
The drug is active in very low doses, and
the dangers of toxicity with potential fatality make the use of the drug for outpatient medication some-
what precarious.
Strophanthu,
however, is formulated with belladonna and valeria in the form of tinc-
tures (1:1:2 ratio) for the oral treatment of vagotonia, extrasystoles, and hypertension. In cases of angina
symptoms of vasomotor origin, a formulation containing equal amounts of
Strophanthus
tincture, vale-
rian tincture, and “nitrous ether spirit” has reportedly been employed with good results.
511
Pharmacokinetics —
Strophanthosides are poorly absorbed through the gut. Proprietary
preparations exist for sublingual administration via the base of the tongue. Only 16% of
K-strophanthoside-a was absorbed when administered per os in a study with 33 human volun-
teers.
1002
Following an intravenous injection of the drug, 73% of the dose administered was excreted
through the kidney, and the half-life of elimination was 99 h. About 70% of the total drug excrement
