Strychnos usambarensis

Family

Loganiaceae

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Synonyms

Strychnos cerasifera Gilg (1895).

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Vernacular names

Blue bitterberry, stipe-fruited strychnos, stipe-fruited monkey orange (En).

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Origin and geographic distribution

Strychnos usambarensis occurs from Guinea east to Nigeria, and from Congo east to Kenya and south to South Africa.

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Uses

The Banyambo people of Rwanda and Tanzania use the root bark and leaves of Strychnos usambarensis to produce arrow poison, sometimes in combination with other plants. In DR Congo the Nduye people mix the powdered root with water and apply this to the nostrils of hunting dogs to improve their scent.
In DR Congo and western Kenya the wood is used for house construction.

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Properties

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. In addition, 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 spp. Strychnos usambarensis 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 Strychnos usambarensis 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. 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. Akagerine has only little antiprotozoal activity. Usambarensine and 5’, 6’-dihydrousambarensine are active against the gram-positive bacteria Staphylococcus aureus, Bacillus subtilis and Mycobacterium smegmatis. Harmane showed no antimicrobial 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 of Strychnos usambarensis 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. Some of the Strychnos alkaloids can be synthesized in vitro in tissue cultures, but most of the syntheses produce a mixture of stereoisomers.

Adulterations and substitutes

Several other tropical African plant species such as Strychnos icaja Baill., Acokanthera schimperi (A.DC.) Schweinf. and Strophanthus spp. are used as substitutes for Strychnos usambarensis to produce arrow poison.

Description

Large liana up to 70 m long, climbing with solitary tendrils, or shrub to small tree up to 10(–15) m tall; stem up to 25 cm in diameter; bark pale or dark grey or grey-brown with darker patches, smooth, inner bark orange; branches with lenticels, usually very dark brown, often covered with a pale skin which splits and peels off, branchlets pale brown, glabrous or short-hairy. Leaves opposite, simple and entire; stipules absent; petiole 2–6 mm long, glabrous; blade ovate to elliptical, 3–8(–16) cm × 1–3.5(–7) cm, base cuneate to rounded, apex acuminate, 3–5-veined from the base. Inflorescence an axillary lax or congested thyrse, solitary or several together, 1–2.5 cm long, few-flowered. Flowers bisexual, regular, 4–5-merous; sepals fused at base, ovate to triangular, up to 1 mm long; corolla tube up to 1.5 mm long, lobes oblong to ovate or triangular, c. 1 mm long, acute, recurved from somewhat below the middle, glabrous or minutely hairy outside, inside with a ring of hairs in the throat, white, yellow or sometimes orange; stamens inserted at the mouth of the corolla tube, exserted; ovary superior, ovoid, 0.5–1 mm long, glabrous, 2-celled, style up to 1.5 mm long, stigma small, head-shaped or sometimes obscurely 2-lobed. Fruit a globose berry 1–2 cm in diameter, often laterally compressed, soft, orange or orange-yellow when ripe, often glaucous, 1-seeded. Seed depressed-globose or ellipsoid, 9–12 mm × 7–11 mm × 5–8 mm, short and densely hairy, smooth.

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Other botanical information

Strychnos comprises about 200 species: about 60 species in Asia, 65 in America and 75 in Africa. Strychnos usambarensis belongs to the section Rouhamon. Strychnos variabilis De Wild., which occurs in Congo and DR Congo, also belongs to this section, and contains at least 20 indole alkaloids. An ethyl acetate and a methanolic extract of the root showed significant anti-malarial activity in vitro.

Growth and development

Strychnos usambarensis is a very adaptable species, varying in habit from shrub to liana or tree.

Ecology

Strychnos usambarensis occurs in lowland and upland rainforest, also in secondary forest, in gallery forest and semi-evergreen and coastal evergreen bushland from sea-level up to 2000 m altitude.

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Harvesting

Root bark, stem bark and leaves intended for trade are usually collected from wild plants. The best time for harvesting is after flowering.

Yield

The total alkaloid content of the leaves is approximately 1% dry weight. The yield of isostrychnopentamine from the leaves is 0.2% (w/w).

Handling after harvest

The root bark, stem bark or leaves are usually dried for later use.

Genetic resources and breeding

Strychnos usambarensis is widespread and occurs in many habitats; it is therefore not likely that it is threatened by genetic erosion.

Prospects

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.

Major references

• Angenot, L., 1971. De l’existence en Afrique centrale d’un poison de flèche curarisant issu du Strychnos usambarensis Gilg. Annales Pharmaceutiques Françaises 9: 353–364.
• Leeuwenberg, A.J.M., 1969. The Loganiaceae of Africa 8. Strychnos 3. Revision of the African species with notes on the extra-African. Mededelingen Landbouwhogeschool Wageningen 69–1. Wageningen, Netherlands. 316 pp.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
• Ohiri, F.C., Verpoorte, R. & Baerheim Svendsen, A., 1983. The African Strychnos species and their alkaloids: a review. Journal of Ethnopharmacology 9(2–3): 167–223.
• Philippe, G., Angenot, L., De Mol, P., Goffin, E., Hayette, M.P., Tits, M. & Frédérich, M., 2005. In vitro screening of some Strychnos species for antiplasmodial activity. Journal of Ethnopharmacology 97(3): 535–539.
• Schwikkard, S. & van Heerden, F.R., 2002. Antimalarial activity of plant metabolites. Natural Product Reports 19: 675–692.
• Terashima, H. & Ichikawa, M., 2003. A comparative ethnobotany of the Mbuti and Efe hunter-gatherers in the Ituri forest, Democratic Republic of Congo. African Study Monographs 24(1–2): 1–168.

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Other references

• Bassleer, R., Depauw-Gillet, M.C., Massart, B., Marnette, J.M., Wiliquet, P., Caprasse, M. & Angenot, L., 1982. Effets de trois alcaloïdes extraits du Strychnos usambarensis sur des cellules cancéreuses en culture. Planta Medica 45: 123–126.
• Bisset, N.G. & Leeuwenberg, A.J.M., 1968. The use of Strychnos species in Central African ordeal and arrow poisons. Lloydia 31: 208–222.
• Bonjean, K.A.P.M., De Pauw-Gillet, M.-C.A.J., Quetin-Leclercq, J., Angenot, L. & Bassleer, R.J.B., 1996. In vitro cytotoxic activity of two potential anticancer drugs isolated from Strychnos: strychnopentamine and usambarensine. Anticancer Research 16(3A): 1129–1137.
• Bosch, J., Bonjoch, J. & Amat, M., 1996. The Strychnos alkaloids. In: Cordell, G.A. (Editor). The Alkaloids 48. Academic Press, San Diego, United States. pp. 75–189.
• Frédérich, M., Bentires-Ali, M., Tits, M., Angenot, L., Greimers, R., Gielen, J., Bours, V. & Merville, M.-P., 2003. Isostrychnopentamine, an indolomonoterpenic alkaloid from Strychnos usambarensis, induces cell cycle arrest and apoptosis in human colon cancer cells. Journal of Pharmacology and Experimental Therapeutics 304: 1103–1110.
• Frédérich, M., Cristino, A., Choi, Y.H., Verpoorte, R., Tits, M., Angenot, L., Prost, E., Nuzillard, J.-M. & Zèches-Hanrot, M., 2004. Chrysopentamine, an antiplasmodial anhydronium base from Strychnos usambarensis leaves. Planta Medica 70: 72–76.
• Frédérich, M., Hayette, M.P., Tits, M., De Mol, P. & Angenot, L., 1999. In vitro activities of Strychnos alkaloids and extracts against Plasmodium falciparum. Antimicrobial Agents and Chemotherapy 43(9): 2328–2331.
• Frédérich, M., Tits, M. & Angenot, L., 1998. Qualitative and quantitative evaluation of bisindole usambarane alkaloids in Strychnos usambarensis roots by high performance liquid chromatography-diode-array. Phytochemical Analysis 9: 63–66.
• Frédérich, M., Tits, M., Goffin, E., Philippe, G., Grellier, P., De Mol, P., Hayette, M.-P. & Angenot, L., 2004. In vitro and in vivo antimalarial properties of isostrychnopentamine, an indolomonoterpenic alkaloid from Strychnos usambarensis. Planta Medica 70(6): 520–525.
• Lovett, J.C., Ruffo, C.K., Gereau, R.E. & Taplin, J.R.D., 2006. Field guide to the moist forest trees of Tanzania. [Internet] Centre for Ecology Law and Policy, Environment Department, University of York, York, United Kingdom. http://www.york.ac.uk/ res/celp/webpages/projects/ecology/ tree%20guide/guide.htm. Accessed February 2007.
• Mitchell, N., 2004. The exploitation and disturbance history of Kakamega Forest, western Kenya. In: Bleher, B. & Dalitz, H. (Editors). BIOTA East Africa Report No. 1, Bielefelder Ökologische Beiträge, Band 20. 77 pp.

Afriref references

Sources of illustration

• Leeuwenberg, A.J.M., 1969. The Loganiaceae of Africa 8. Strychnos 3. Revision of the African species with notes on the extra-African. Mededelingen Landbouwhogeschool Wageningen 69–1. Wageningen, Netherlands. 316 pp.

Author(s)

•	N.S. Alvarez Cruz Unidad de Medio Ambiente, Delegación del CITMA, Cor. Legon 268 / Henry Reeve y Carlos Roloff, Sancti Spiritus 60100, Cuba

Editors

•	G.H. Schmelzer PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	A. Gurib-Fakim Faculty of Science, University of Mauritius, Réduit, Mauritius

Associate editors

•	C.H. Bosch PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	M.S.J. Simmonds Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, United Kingdom
•	R. Arroo Leicester School of Pharmacy, Natural Products Research, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom
•	A. de Ruijter PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

General editors

•	R.H.M.J. Lemmens PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	L.P.A. Oyen PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Photo editor

•	A. de Ruijter PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Alvarez Cruz, N.S., 2007. Strychnos usambarensis Gilg ex Engl. [Internet] Record from PROTA4U. Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>. Accessed .

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