Pausinystalia johimbe (PROTA)
Pausinystalia johimbe (K.Schum.) Pierre ex Du Puy & Beille
- Protologue: Act. Soc. Linn. Bordeaux 61: 130 (1906).
- Family: Rubiaceae
- Johimbe, yohimbe (En).
- Yohimbe, démarreur (Fr).
- Pau de Cabinda (Po).
Origin and geographic distribution
Pausinystalia johimbe is distributed from southern Nigeria to Cabinda (Angola). Its occurrence in DR Congo needs to be confirmed.
Young stems are used as poles in construction. The wood is used as fuelwood. The bark is used in house construction, and the inner bark is utilized for making straps for hunting panniers. Young saplings are used as snare-trap mechanisms.
Bark preparations are widely used as aphrodisiacs and stimulants. In Cameroon, for instance, the bark is popularly known as ‘the African viagra’. In Gabon small quantities of the bark are chewed to dispel sleep, while as an aphrodisiac it is used in larger quantities or more frequently. The bark is also used as a local anaesthetic, a hallucinogen, for the treatment of angina, against constipation and intestinal worms, as a performance enhancer for athletes, and to increase the clarity of singers’ voices. In Congo a bark decoction is drunk for the treatment of pelvic pain. In Gabon the bark is used as a fish poison.
The bark is the standard source of the alkaloid yohimbine, which is included in various European pharmacopoeias for its sympatholytic, hypotensive and local anaesthetic activity. Yohimbine-based products are widely used as aphrodisiacs in the Western World, either through pharmaceutical channels or herbal medicine markets. The most common use of yohimbine-based drugs in western medicine is in the treatment of diabetes-related male impotence. Yohimbine-based products are also used as food supplements for body weight reduction. In the United States they are recorded to be used as food supplements to substitute anabolic steroids and improve athletic performance. However, in a study investigating the alkaloid content of 26 yohimbe products sold in retail health food outlets throughout the United States, 9 of the products appeared not to contain any yohimbine, 8 only contained trace amounts, and the product with the highest yohimbine content contained only 0.05%. In the United Kingdom yohimbine-based drugs have become fashionable as ‘herbal highs’.
Production and international trade
The bark is extensively traded in local markets and exported. Most of the bark entering commercial trade comes from Cameroon. In 1985–1991 the annual exports of bark from Cameroon amounted to 286 t, of which 65% to the Netherlands, 18% to Germany, 11% to Belgium/Luxembourg and 6% to France. The bark exports from Cameroon in the season 1997–1998 amounted to 715 t, with a value of about US$ 600,000. However, a large proportion of the exported bark is probably not from Pausinystalia johimbe but from Pausinystalia macroceras (K.Schum.) Pierre, which has a much lower yohimbine content.
The heartwood is ochre-yellow and not clearly demarcated from the thin, yellow sapwood. The grain is fine. The wood is moderately heavy, with a density of 650–750 kg/m³ at 12% moisture content, and moderately hard.
The bast fibre cells are 0.7–1.6 mm long, with a diameter of 22–29 μm. The bark of Pausinystalia johimbe contains up to 6% alkaloids. The alkaloid content is highest in the root bark and the bark of the bole, lower in the bark of the branches, and very low in the leaves. Within the bole, the alkaloid content increases from the base upwards. The alkaloids present in Pausinystalia johimbe include yohimbine (10–15%), mesoyohimbine, yohimbinine, corynanthine, alloyohimbine and ajamalicine.
Yohimbine (also known as aphrodine, quebrachine or corynine) is a selective inhibitor of α-2-adrenergenic receptors. At low doses it has hypertensive activity, while at higher doses it is hypotensive, through vasodilation of peripheral vessels. Yohimbine raises heart rate and norepinephrine levels. The use of yohimbine as an aphrodisiac is attributed to its dilating effect on the blood vessels of the sexual organs, thus increasing blood supply, while it also provides an enhancement of the reflexes involved in the control of ejaculation. Tests have shown that treatment with yohimbine indeed results in increased libido and easier ejaculation. The effects of yohimbine on smooth muscles favours tonus and movement of the intestine. It also acts on α-2-adrenergenic receptors of adipocytes, resulting in increased lipolysis. However, double-blind trials on the effectiveness of yohimbine for body-weight reduction gave conflicting results, and it is therefore unclear whether yohimbine is effective in reducing body weight. A wide range of adverse effects of the use of yohimbine have been recorded, including hypertension, mania, bronchospasm, anxiety, agitation, hallucinations, vertigo, stomach problems, headache and weakness. It may also interact with antidepressants. Especially people with hypertension, prostate problems or heart diseases are warned against using yohimbine-based products.
Ajamalicine also has vasodilating activity. Corynanthine closely resembles yohimbine, but is more active as a sympatholytic agent and less toxic. The bark also contains tannins.
Adulterations and substitutes
Pausinystalia johimbe bark is frequently adulterated with the bark of other Pausinystalia and Corynanthe spp., which have a lower yohimbine content.
- Evergreen, medium-sized tree up to 30(–35) m tall; bole straight, up to 50(–60) cm in diameter, without buttresses but grooved at base; bark easy to peel off, bitter-tasting, bark surface longitudinally fissured, with transverse cracks, grey to reddish brown, inner bark fibrous, pinkish, turning reddish brown on exposure; crown compact, with branches in whorls.
- Leaves in whorls of 3, simple; stipules 1.5–2 cm long, glabrous, caducous; petiole up to 5(–8) mm long; blade obovate or oblanceolate, (11–)13–47 cm × 5–17.5(–19) cm, base cordate, cuneate or rounded, apex short-acuminate, margin often wavy, glabrous, pinnately veined with (8–)10–20 pairs of lateral veins.
- Inflorescence a terminal or axillary panicle 5–21(–30) cm × 9–15 cm, branched in whorls of 3, with flowers in clusters at the ends of branches, main axes glabrous; peduncle 0.5–5 cm long, with 3 ridges.
- Flowers bisexual, regular, (4–)5(–6)-merous, fragrant; calyx consisting with short tube and triangular or rounded lobes c. 0.5 mm long, hairy; corolla white, sometimes yellowish, red or purple, with tube consisting of a basal narrow part c. 0.5 mm long and an apical bladder 1.5–2.5 mm long, hairy inside, glabrous outside, lobes erect, shortly toothed, each with a linear appendage 8–20(–25) mm long; stamens attached at the base of the corolla bladder, alternating with the lobes, sessile; ovary inferior, 2(–3)-celled, style 1–2 mm long, stigma 2-lobed.
- Fruit an oblong, compressed capsule 10–16 mm × 5–7 mm, dehiscing with 4 valves, many-seeded.
- Seeds oblong, 8–12 mm × 1.5–2.5 mm, compressed, winged.
Other botanical information
Pausinystalia comprises 5 species, and occurs in West and Central Africa. It is closely related to Corynanthe.
Pausinystalia johimbe can be distinguished from Pausinystalia macroceras by its larger leaves with shorter or no petioles. Furthermore, the bark of Pausinystalia johimbe is tasting extremely bitter and is easy to peel off, whereas that of Pausinystalia macroceras is less bitter and difficult to peel off. Differences in slash characteristics, often mentioned as being distinguishing, are not reliable.
Growth and development
Light is necessary for germination and good seedling growth, and the survival rate of seedlings under a closed canopy is very low. Growth is usually fast, but the bole diameter never becomes larger than 50–60 cm. Throughout its range, Pausinystalia johimbe usually flowers in August–February, and bears fruits in September–March. Pollination is probably by insects. Large amounts of seeds are produced each year. The seeds are dispersed by wind. Pausinystalia johimbe coppices well from stumps, producing strong, highly phototropic shoots.
Pausinystalia johimbe occurs in evergreen lowland forest, in primary as well as secondary forest, at relatively low densities.
Propagation and planting
Vegetative propagation trials with single-node leafy cuttings have given good results. Propagation with seeds is also done, but seeds are difficult to collect. Furthermore, the survival rate of seedlings was very low in experiments. Wildlings collected from the forest showed poor survival and low growth rates.
Although Pausinystalia johimbe is often stated to be common, inventories in Cameroon and Equatorial Guinea in the 1990s indicated that there are on average only 15 plants/ha with a diameter over 1 cm and 4 trees/ha with a diameter over 10 cm.
The World Agroforestry Centre (ICRAF) has initiated a research programme to investigate the domestication potential of Pausinystalia johimbe and its possible inclusion in agroforestry systems. Initial results have shown that it will readily grow in association with annual food crops.
Diseases and pests
Removal of large bark surfaces can lead to stem borers penetrating the unprotected stem and killing the tree.
Trees are harvested when they have reached a bole diameter of about 10 cm. As yohimbine levels are highest in the rainy season, harvesting is a seasonal activity. The bark is usually stripped after the tree has been felled for this purpose, making exploitation unsustainable. It would be better to harvest bark strips from standing trees, which will stay alive and renew the bark in 2 years. However, harvesters often claim that the tree will die anyway after removal of part of the bark, because of stem borer attacks. Although a permit is required for harvesting the bark in Cameroon, it is often done by local people who are paid for delivery to contractors. The bark may also be harvested by employees of logging companies after the felling of timber trees in an area.
Handling after harvest
The bark is marketed in dried flat or curved pieces up to 1 m long, or ground.
The high demand for medicines based on the bark of Pausinystalia johimbe has led to over-exploitation and may lead to local scarcity of the species, if not long-term endangerment.
The wood is of good quality, but the relatively small bole diameters limit its usability. Nevertheless, it has been suggested as a suitable substitute for Khaya ivorensis A.Chev. Probably, however, Pausinystalia johimbe will remain more important as a source of yohimbine and local medicine than as a source of timber.
The high demand for medicines based on the bark has led to over-exploitation of natural populations. The tree is easily vegetatively propagated, however, and may have potential for inclusion in agroforestry systems, which could help to relieve the pressure on natural populations. For this purpose, it has been recommended to carry out studies on the breeding system (the presence of self-incompatibility) of Pausinystalia johimbe, and on seed dormancy, seed germination and seedling survival.
Care should be taken with the use of yohimbine-based products for medicinal purposes, as adverse side effects have been recorded. As the content of yohimbine and other alkaloids in the bark may vary widely, the use of crude products is even more dangerous than that of products with a known amount of yohimbine. Therefore, yohimbine-based products should be taken cautiously and only under supervision of a specialist, and not as self-medication.
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Correct citation of this article
Jiofack Tafokou, R.B., 2012. Pausinystalia johimbe (K.Schum.) Pierre ex Beille. In: Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 27 November 2022.