Common Name:

General Information

Strychnos usambarensis is a vigorous climbing shrub producing stems that can be up to 70 metres long. The plant can grow into the canopy of the forest, attaching itself by means of tendrils. When growing in a more open position, it can sometimes grow more as a shrub or tree up to 15 metres tall with a bole 25cm in diameter[].
The plant is harvested from the wild for local use of its wood. It is a source of alkaloids that are used in conventional medicine.

Known Hazards

The root bark and leaves are used to produce arrow poison, sometimes in combination with other plants[].

Botanical References

Range

Africa - Guinea to Nigeria; Congo to Kenya and south to Zambia, Zimbabwe, Mozambique and northern S. Africa.

Habitat

Lowland and upland rainforest, also in secondary forest, in gallery forest and semi-evergreen and coastal evergreen bushland from sea-level up to 2,000 metres[].

Properties

Medicinal Rating
Other Uses Rating
Habit	Climber
Height	30.00 m
Cultivation Status	Wild

Cultivation Details

Not known

Edible Uses

None known

Medicinal

Strychnos usambarensis is not used for medicinal purposes in Africa because of its toxicity. Several of its alkaloids show promising anticancer or antimalarial activities, and more research into the pharmacological activities of the compounds seems warranted[].
Strychnos usambarensis is the best investigated African Strychnos species and more than 60 indole alkaloids have been isolated from it. The ones that have been identified so far are predominantly dimeric terpenoid indole alkaloids[].
The root bark contains tertiary alkaloids and several important quaternary alkaloids and anhydronium bases. Among these are the retuline class alkaloids C-dihydrotoxiferine, C-curarine and C-calebassine and the monomeric C-fluorocurarine, which are also the active principles of calabash curare obtained from South American Strychnos species[].
The root bark also contains the less active afrocurarine, the monomeric tetracyclic alkaloid akagerine, the non-terpenoid alkaloids harmane and melinonine F and the monoquaternary alkaloids malindine and isomalindine, which belong to the group of trinitrogenated alkaloids. Four root alkaloids, the dimeric usambarensines, are of the corynanthean class[].
The leaf alkaloids are all of the corynanthean class, and belong to the usambarine group and the dimeric oxindole group. The main component of the leaves is the oxindole strychnofoline. Apart from alkaloids also known from other plant species, Strychnos usambarensis leaves contain some rare alkaloids with 5 nitrogen atoms such as strychnopentamine, its derivatives chrysopentamine, isostrychnopentamine and the oxindole strychnophylline[].
The muscle paralyzing, curare-like effect of the root bark is caused by the quaternary alkaloids, which block the excitation of the skeletal muscles. The paralyzing effect can be antagonized by acetylcholine. At higher doses the alkaloids cause a series of side-effects: drop in blood pressure, blocking of the vagus nerve, change in cardiac rate and frequency of respiration[[].
Malindine also has a strong muscle relaxant activity, which is not antagonized by acetylcholine and is not of the curare type[].
Akagerine and its derivatives are potent convulsant agents, but 100 times less active than strychnine[].
The usambarensines have no paralyzing effect on skeletal muscles, but do have an atropine-like and spasmolytic activity on smooth muscles[].
Harmane induces enrichment of biogene amines such as serotonine in the brain. In small doses it causes hallucinations, in high doses convulsions and respiratory paralysis[]. Harmane showed no antimicrobial activity[].
Strychnopentamine and 5’,6’-dihydrousambarensine showed strong activity against Plasmodium falciparum in vitro, but were inactive against Plasmodium berghei in vivo. However, isostrychnopentamine has an interesting antiplasmodial activity both in vitro against various chloroquine-resistant and chloroquine-sensitive strains of Plasmodium falciparum and in vivo against chloroquine-sensitive strains of rodent-infecting Plasmodium berghei and Plasmodium vinckei[].
Usambarine, usambarensine and 18,19-dihydrousambarine were less active against Plasmodium falciparum in vitro, but highly active against Entamoeba histolytica in vitro[].
Usambarensine and 5’, 6’-dihydrousambarensine are active against the gram-positive bacteria Staphylococcus aureus, Bacillus subtilis and Mycobacterium smegmatis.[].
Akagerine has only little antiprotozoal activity[].
Many of the Strychnos usambarensis alkaloids were shown to be markedly toxic to a number of tumour lines[]. A chloroform extract of the leaves is active against lymphatic leukaemia P-388 in mice in vivo. Especially strychnopentamine, chrysopentamine and isostrychnopentamine are regarded as potential anticancer agents[].
Curare alkaloids have played an important role in reducing the risk of anaesthesia, since much smaller amounts of anaesthetic are necessary. The drugs have made it possible to achieve adequate muscle relaxation for all clinical requirements[].

Other Uses

The wood is used for house construction[].

Propagation

Seed -

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