Vernacular names

• Iboga, eboka, bitter grass, sacred wood, leaf of God (En).
• Iboga, eboka, éboga, eraga, bois sacré, bois amer, dibughi (Fr).
• Dihoa, lihoka (Po).

Origin and geographic distribution

Tabernanthe iboga is distributed naturally in Central Africa, from Cameroon east to eastern DR Congo and south to central Angola. It was once collected in Tanzania. Tabernanthe iboga is cultivated in several countries in West Africa, e.g. Côte d’Ivoire.

Uses

Tabernanthe iboga is well known in Central Africa, as the root is very important in the initiation ceremonies of the Bwiti tradition in Gabon, which has expanded to southern Cameroon, Equatorial Guinea Congo and DR Congo. The root bark is eaten whole, or crushed and ground, rolled into small balls, sometimes mixed with other ingredients; sometimes a decoction of the crushed roots is taken. The root is mainly employed as a hallucinogenic, a catalyst for spiritual discovery, and to seek information from ancestors and the spirit world, hence ‘coming to terms with death’. After the initiation ceremony, the initiate is reborn as an adult in the tribe, having been cleansed of illnesses and socio-psychological blockages accumulated during childhood. Iboga is taken in these ceremonies in large quantities. Ceremonies are also held for diagnostic or therapeutic reasons, and the quantities of iboga taken there are in general much lower, allowing the participant a certain agility and endurance. A root decoction can also be taken as a tonic to combat tiredness, hunger and thirst when it is necessary to overcome physical stress, e.g. for hunting or formerly in tribal wars. It is also considered aphrodisiac, as is the leaf decoction. A root decoction is taken as a febrifuge. In DR Congo the decoction is used for eye drops to treat conjunctivitis. The pounded roots are also used in the curing ceremony (called ‘zebola’) for psychosomatic afflictions. In Congo a root macerate in palm wine is taken to soothe coughs, and the root decoction is drunk to treat urinary infections. In traditional medicine, the latex is taken as an anthelmintic and warmed leaves are rubbed on the gums to calm toothache, as they have an anaesthetic activity. The latex is mixed with Periploca nigrescens Afzel. and/or Strophanthus spp. and is used as arrow poison.

In the 1980s iboga became popular in the United States and Europe as a non-addictive interrupter of drug dependency, but soon thereafter it was classified as a hallucinogen and dangerous substance in the United States, where it is therefore illegal to buy, sell, or possess it without a licence. Its possession is also prohibited in Belgium, Switzerland, Sweden and Australia. There has been renewed interest in iboga since the late 1990s.

Production and international trade

The roots or root bark of Tabernanthe iboga can be found commonly in local markets and pharmacies. At present, the market for Tabernanthe iboga is increasing because of the use of iboga outside Africa for the treatment of addictions to tobacco, alcohol and drugs, and also to treat psychological disorders. The trade of Tabernanthe iboga products is most important in Gabon.

Tabernanthe iboga products, particularly the rootbark, are mostly bought and sold by members of the Bwiti society and traditional healers. Statistical information on trade is scarce. Powdered iboga root bark was sold on the local market of Libreville (Gabon) in 2005 at 5000 Fcfa (US$ 7.6) for 200 ml, while 1 l is sold at 15,000 Fcfa (US$ 22.8). In 2004 a Gabonese trader exported root bark to Europe with an estimated value of 6 million Fcfa (US$ 9100).

The roots are imported by several countries, e.g. France, Netherlands, Germany, United Kingdom, Canada and countries in the Caribbean. On internet, prices of powdered root ranged in 2005 from US$ 2.35 per g to US$ 1.5 per g depending on the quantity; prices of powdered root bark ranged from US$ 4.7 per g to US$ 2.6 per g also depending on the quantity; prices of ibogaine hydrochloride (98% pure) range from US$ 150 per g to US$ 300 per g; seeds were sold in packages of 5 seeds for US$ 19.

Properties

The active compounds in the root, root bark, stem bark, leaves and seeds of Tabernanthe iboga are indole alkaloids. About 20 have been identified so far; the highest concentrations occur in the root bark (5–6%), followed by the roots (1–2.5%), stem bark (2%), seed (1%) and leaves (0.4–0.8%). Ibogaine (ibogan class) is the most important alkaloid present in all plant parts except the seeds. Ibogaine can be synthesized from nicotinamide via a 13- or 14-step process, but the yield is too low to be economically attractive. The main activities of ibogaine are on the central nervous system and on the cardiovascular system. Alkaloids structurally similar to ibogaine have analogous effects.

At low doses, ibogaine exerts primarily a stimulant effect, increasing alertness and reducing fatigue, hunger and thirst. At higher doses, the primary effects are hallucinations, with unpleasant possible side effects such as anxiety and depression with fear or rage. The peak effect is reached 1–3 hours after swallowing the drug; it subsides gradually, ending in complete insomnia and lethargy. These effects can last for 2–5 days. Apart from the psychological effects, the physical effects include tremor, light sensitivity, nausea and vomiting, loss of muscular coordination and prolonged and often painful muscle spasms, all in a dose-dependent way. Toxic doses may produce convulsions, paralysis and death from respiratory arrest. Most activities have been tested with purified ibogaine, but during initiation ceremonies powdered root bark is usually taken, which is more powerful as it contains a range of related alkaloids. Ibogaine is a potent cholinesterase inhibitor, and the root extract is even 100 times stronger in its inhibitory effect because of the additional effects of the alkaloids tabernanthine, ibogamine and the more distantly related iboluteine. This property contributes to the anti-fatigue properties of ibogaine, and results from an increased sensitivity to adrenaline, bringing about a transient excited state of the sympathic nervous system. Despite the reputation of iboga as an aphrodisiac, ibogaine did not produce a stimulation of sexual functions in tests with dogs, cats and sheep. Not does ibogaine have a significant analgesic effect in mice

Recent research indicates that ibogaine has a novel pharmacological mechanism of action, acting strongly on a variety of different receptors in the brain, resulting from complex interactions between neurotransmitter systems. There is no consensus yet on how ibogaine works precisely, but it is known to inhibit the re-uptake of the neurotransmitter serotonin, which can cause hallucinations. However, the suggestion by laymen that ibogaine has considerable potential in the field of psychotherapy is premature. Research on animals and humans reveal that ibogaine is converted in the liver to noribogaine, which fills opiate receptors, thus eliminating withdrawal symptoms. Ibogaine also stimulates nicotinic receptors in the cerebellum, which contributes to modulating the dopamine reward circuit. At high doses though, ibogaine is toxic as it destroys neurons in the cerebellum.

Research with animals and anecdotal reports of humans suggest that ibogaine has considerable potential in treating addictions to heroin, cocaine, alcohol, nicotine, caffeine, amphetamine, desoxyephedrine or methadone, or combinations of these. Several methods to arrest the physiological and psychological aspects of dependency on drugs by using ibogaine have been patented in the United States. Treatments are claimed to be effective for 70–100% of the cases. However, the serious side effects of ibogaine make its use potentially harmful and additional clinical studies are needed to determine if and how it can be used safely. The side effects of ibogaine are not present in the ibogaine congener 18-methoxycoronaridine (18-MC), nor in the metabolite noribogaine, and these compounds thus have potential in safe and effective treatments. Meanwhile, there are some clinics, e.g. in the Caribbean, that offer a controlled ibogaine treatment, and in Europe illicit treatments are available without medical facilities. In addition, ibogaine and iboga extracts have become available through the internet.

Adulterations and substitutes

Several other Apocynaceae genera also contain compounds related to ibogaine, but they contain ibogaine as a minor compound only, e.g. Tabernaemontana and Voacanga.

Description

Shrub up to 4 m tall, repeatedly dichotomously branched, with white latex in all parts, glabrous to hairy; trunk up to 10 cm in diameter; bark pale to dark grey, smooth. Leaves opposite, simple and entire; stipules absent; petiole 1–13 mm long, with three or more rows of colleters in the axils; blade narrowly elliptical, elliptical or narrowly obovate, 2.5–22 cm × 1–10 cm, base slightly cordate to cuneate, apex acuminate, pinnately veined with 7–20 pairs of lateral veins. Inflorescence an irregularly corymb 3–7 cm × 2–4 cm, 2 together just above the forks of the branches, few- to many-flowered; peduncle 0.5–4.5 cm long, fairly slender; bracts as long as the sepals, sparsely hairy at the apex. Flowers bisexual, regular, 5-merous, fragrant; pedicel 2–17 mm long, thickened at apex; sepals almost free, ovate to triangular, 1–3 mm long, apex acuminate, persistent in fruit; corolla tube almost cylindrical to urn-shaped 5.5–8.5 mm × 1.5–3.5 mm, contracted at base, lobes orbicular to obliquely ovate, 2.5–6 mm long, with obtuse or rounded apex, in bud overlapping to the left, undulate, spreading and recurved later, hairy inside from the insertion of the stamens to the mouth, white or cream, usually with red to purple dots or stripes in 5 groups in the throat; stamens inserted 2.5–4 mm above the corolla base, included, anthers almost sessile, base sagittate; ovary superior, only basally 2-celled, surrounded by a disk, style slender, pistil head composed of a basal ring, an almost globose central part with 5 grooves and 2 slender apical lobes. Fruit a globose, ellipsoid or ovoid berry 3–6.5 cm long, apex rounded, obtuse, acute or acuminate, pendulous, smooth or less often bumpy, glabrous, yellow to red, many-seeded, with the seeds in spongy, white pulp. Seeds ellipsoid, 7–10 mm long, brain-like deeply indented. Seedling with epigeal germination, taproot firm, cotyledons leafy, rounded, epicotyl 3.5–7.5 cm long, glabrous.

Other botanical information

Tabernanthe comprises 2 species, both restricted to Central Africa: Tabernanthe iboga and Tabernanthe elliptica (Stapf) Leeuwenb. Tabernanthe elliptica occurs in Congo, DR Congo and Angola and differs mainly from Tabernanthe iboga in having only 4–7 pairs of lateral leaf veins and having fruits consisting of 2 separate follicles bearing soft blunt prickles. Of the total alkaloids in the root bark (5.6%) and stem bark (2.4%), about 80% is ibogaine. The leaves do not contain ibogaine. Hybridization occurs between the 2 species, resulting in plants with the carpels more or less fused in fruit, without or with a few blunt prickles. The fruits of Tabernanthe iboga are quite variable; in Gabon plants with ovoid fruits are most commonly used in ceremonies.

Growth and development

The seedling of Tabernanthe iboga grows rhythmically, extending by flushes, becoming about 60 cm tall in 3 years. The juvenile period lasts 5–6 years. The plant develops according to the architectural growth model of Leeuwenberg characterized by a monopodial orthotropic trunk, which ends in a terminal inflorescence. After flowering the 2 uppermost axillary buds develop into branches, so that the growth is sympodial and the infructescence seems to be axillary. Flowering and fruiting occurs almost throughout the year, but mostly between September and February. The fruits take 5–6 months to mature. Tabernanthe iboga regenerates well by forming shoots from the trunk.

Ecology

Tabernanthe iboga occurs in the forest understorey, sometimes in riverine or swamp forest or relatively wet savanna, from sea-level to 1500 m altitude. In Gabon it is dominant in forest along the Atlantic coast, between Cocobeach and Ndindi. The seeds are dispersed by elephants as they feed on the fruit.

Propagation and planting

Propagation of Tabernanthe iboga is by fresh seed or by cuttings. Germination is slow and irregular, ranging from a few weeks to a few months. Scarification prior to sowing increases the germination rate considerably, although this is rarely done in home gardens. After a few months the seed coat dries out, making it difficult for the seedling to emerge. Seedlings need to be protected from the sun. They can be transplanted to their final location after 2–3 months, when the root has become twice as long as the stem.

Cuttings of about 25 cm long and 1 cm in stem diameter root easily in humid soil. These cuttings flower already after 4 months. Tabernanthe iboga can be propagated through tissue culture.

Management

Tabernanthe iboga is commonly cultivated in home gardens. Once established, individual plants grow fast and require little maintenance, but need to be protected from fire.

Harvesting

In the wild, whole plants of Tabernanthe iboga are uprooted to harvest the roots. This leads to large-scale destruction of natural stands. In home gardens, only a part of the roots is harvested. The roots can be harvested throughout the year although it is easier during the rainy season between October and May, as the soil is easier to work. Larger quantities are mainly collected from wild stands.

Handling after harvest

The fresh roots are transported in jute bags. They are washed and sun-dried for local use or for the market. The bark of the root is then separated, and is again left to dry in the sun for 7–10 days, after which it is pounded and sieved through a coarse mesh. The powder is kept dry in bottles.

Genetic resources

No germplasm collections of Tabernanthe iboga exist, and as large quantities of the plants are harvested from the wild, it is likely that the genetic diversity will be threatened in the near future. Also, an inventory of the morphological variation is needed to clarify the diversity within in the species, especially in the shape of the fruit. The government of Gabon considers iboga a national patrimony; however, there is no law protecting it against overexploitation.

Prospects

Tabernanthe iboga is a plant with considerable socio-economic importance in Gabon and neighbouring parts of Africa because of its role in the Bwiti tradition, and outside Gabon because the root bark or purified ibogaine is used in Europe and America in treating addictions to drugs, alcohol and smoking. Apart from the need to investigate whether ibogaine really does suppress the craving for drugs, its toxic side-effects need to be elucidated. Tabernanthe iboga is not yet threatened in its natural environment, but as most plants are harvested from the wild, and whole plants are uprooted, it may become endangered in the near future when demand remains high. More research on cultivation practices and methods of propagation of superior plant types is warranted. Iboga has ornamental value, especially when in flower and fruit.