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Terry C.H. Sunderland, Marie-Laure Ngo-Mpeck, Zacharie Tchoundjeu and Amougou Akoa


Pausinystalia johimbe (K. Schum.) Pierre ex Bielle, or yohimbe, is a widely-used medicinal plant, the bark of which is used to treat male organic impotence. The species is exploited in large quantities for both the local medicinal and growing export markets. Recent advancements in the development of yohimbe-based remedies have led to an increased demand for the export market. This demand is generating considerable over-exploitation and local scarcity of the species.

Concerned over the fact that future supplies might be compromised by current levels of over-exploitation, Boehringer Ingelheim, a German pharmaceutical company which import P. johimbe bark directly from Cameroon through Plantecam, a subsidiary of Laboratoires Fournier, commissioned the International Centre for Research in Agroforestry (ICRAF) to undertake a pilot study on the ethnobotany, ecology and natural distribution of the species. The study also assessed the effects of current harvesting practices. Further information was gathered with a view to include the species as part of ICRAF's domestication programme for use in agroforestry systems. That field research forms the basis of this paper.

Key words: Pausinystalia johimbe, yohimbe, medicinal plants, cultivation

1. Introduction

Pausinystalia johimbe is a tree native to the coastal forests of Central Africa and is distributed from South East Nigeria to the Congolese Mayombe (Vivien and Faure, 1985). Its bark contains up to 6% of a mixture of alkaloids, the principle one being yohimbine (Tyler, 1993) which is also known as aphrodine, quebrachine or corynine (Lawrence Review of Natural Products, 1990). P. johimbe is used extensively as part of traditional health care systems. Its many recorded uses vary from being used directly as an aphrodisiac (Small and Adams, 1922; Greenish, 1929; Ainslie, 1937; Dalziel, 1937; Raponda-Walker and Sillans, 1961; Motte, 1980; Farnsworth, 1984; Oliver-Beyer, 1986; Tyler, 1993) to that of a local anaesthetic (Greenish, 1929; Oliver Beyer, 1986), a mild stimulant to prevent drowsiness (Raponda-Walker and Sillans, 1961; Obama pers. comm.; author pers. obs), a hallucinogen (Tyler, 1993), a treatment for angina (Lawrence Review of Natural Products, 1990), a hypertensive (Oliver-Beyer, 1986; Lawrence Review of Natural Products, 1990), a general tonic (Ainslie, 1937), a performance enhancer for athletes and as a remedy to increase the clarity of the voices of singers during long festivals (Motte, 1980), an ichthytoxicant, and as a tonic to increase the resilience of hunting dogs (Raponda-Walker and Sillans, 1961).

In addition to its widespread local use, the species has been long exported to Europe for western medicine in both prescription and herbal markets. The most common use of yohimbine-based prescription drugs today is in the treatment of diabetes-related male organic impotence (Lawrence Review of Natural Products, 1990; Vaughan, pers comm.). Sexual stimulant products available over-the-counter often contain yohimbine. In the United Kingdom, yohimbine-containing drugs have become fashionable as one of the "herbal highs" reported in the British press (Castle, 1997) and yohimbe-based products have long been a common sight in "sex-shops" in Europe (Tyler, 1993).

Pfizer, a United States pharmaceutical company, has recently launched a new pharmaceutical for organic impotence which is not derived from yohimbe. The name of the drug is Sildenafil but is marketed under the name Viagra (Montague, 1997). This drug has been the recent focus of huge media attention and has created massive public interest in the availability of so-called aphrodisiacs and cures for impotence. This interest has had a knock-on effect and has led to a resurgence of sales in more easily-available herbals remedies, in particular those that are yohimbe-based (Laird, pers. comm.).

2. Autoecology

2.1. Natural distribution and population structure

P. johimbe is found within the forest type classified by Letouzey (1985) as Atlantic Biafran Evergreen Forest with Caesalpiniaceae, an extensive forest formation extending from South East Nigeria through Cameroon, Equatorial Guinea, Gabon and Congo Brazzaville (Vivien and Faure, 1985). P. johimbe is a fast-growing tree but does not reach a great diameter (a recorded maximum of ca. 50 cm dbh). This seems to be a natural feature of the genus and is not regarded as being a direct result of over-exploitation of the larger size class individuals.

P. johimbe has been referred to as "common" (Raponda-Walker and Sillans, 1960). However, it would seem that the species, whilst not being rare, is far from being regarded as common. Recent inventory data from Cameroon and Equatorial Guinea suggests that there are, on average, 15 trees >1 cm dbh / ha with only 4 trees >10 cm dbh / ha trees that are potentially harvestable (Sunderland et al., 1997). With this number of trees/ha, we could not support the premise that the species is common.

2.2. Reproductive ecology

The light winged seeds of P. johimbe are wind dispersed and their lightness and winged structure mean that they can travel long distances. Consequently, regeneration is not commonly found close to the mother tree and in fact the closest recruit found was 25m from the parent. More commonly, in fact almost exclusively, seedlings were found without the presence of parent trees, indicating long-distance dispersal.

Although the species occurs mainly in closed-canopy forest, light is needed for seed germination and seedling development. Few seedlings survive in closed-canopy forest, except in areas of light to moderate disturbance and the survival rate of seedlings under a closed canopy is extremely low, suggesting that P. johimbe is a light demander in the early stages of regeneration. Similar observations have recently been made with Lovoa trichilioides, an important commercial timber species (Tchoundjeu, in press).

Table 1: Cumulative inventory data of P. johimbe from field sites in Cameroon and Equatorial Guinea (Sunderland et al., 1997).

Study site

Vegetation description

Sampling method

Sample area

No of stems >1cm dbh

Stems/ha >10cm dbh

Campo F.R.


Early -mid secondary






Campo F.R.


Mid-late secondary






Campo F.R.


Closed canopy forest

100mx100m square plot




Ntole F.R.

E. Guinea

Closed canopy forest

500mx10m transect




Ntole F.R.

E. Guinea

Closed canopy forest (lightly disturbed)

1000mx10m transect




Ntole F.R.

E. Guinea

Closed canopy forest

1000mx10m transect





E. Guinea

Closed canopy forest (20 yrs post-logging)

500mx10m transect





3. Sustainability

3.1. Current commercial P. johimbe bark exploitation practices in Cameroon

All P. johimbe bark is currently exploited from wild populations. This exploitation currently takes place exclusively in Cameroon, although interest is currently being shown in the possibility of exploitation in Equatorial Guinea and Gabon. Interestingly, much of the exploitation of P. johimbe is related to timber prospecting with individual stems of the species being identified during the inventories preceding exploitation. After the timber harvesting activities are completed, the yohimbe trees are then also felled and stripped, often by the logging company employees.

Currently, Plantecam is the sole supplier of P. johimbe bark to Europe and currently supplies around 100 tons annually (120 tonnes in 1996 (Simons, 1997)). Unlike the situation where Plantecam has their own collection teams providing Prunus africana bark (up to 33% of the total) for their factory, all of the P. johimbe bark is exploited by outside contractors. These contractors are registered local businesses who have licenses to exploit medicinal plants. These licenses are provided by the Forestry Department. (See Box 1.) Plantecam state that they will not accept plant material from companies or individuals without these licenses (Nkuinkeu, pers. comm.).

In actual fact, however, the majority of bark is collected by local people who are paid at the roadside for the delivery of bark. These local people do not have any permits or authorisation to exploit P. johimbe and, unbeknown to Plantecam who claim to be following the letter of the law, are supplying bark illegally to the contractors. Thus Plantecam, in turn, may be supplied with illegally exploited bark.

Figure 1.Cumulative size-class distribution curve of Pausinystalia johimbe in field sites in Cameroon and Equatorial Guinea

Figure 2. Unsustainable exploitation of Pausinystalia johimbe (Photo: T. Sunderland).

Box 1: Permis d'exploitation

The large scale exploitation of non-timber forestry products such as medicinal plants is subject to the acquiring of a permis d'exploitation. This permit determines the quantities to be exploited or collected within a specified geographic area. The volume or amount of material allowed to be exploited depends on the desired material (e.g. fruits, bark, leaves etc.). This quota would be set by the Department of Forestry, although base line and monitoring data for estimating potential sustainable yield is woefully incomplete. The length of the exploitation permit would not usually exceed one year (National Forestry Law no. 94/01; article 56; October 1994), except by special arrangement. For example, Plantecam has permits for Prunus africana exploitation issued for a period of up to three years duration (Cunningham and Mbenkum, 1993). Exploitation permits also apply to special products, which could include medicinal species or those which are of particular interest. Even if special products are found on lands belonging to private individuals, they remain the property of the State, except where the said products have been acquired by the individual concerned.

Prices paid per kilo of bark by Plantecam range from 125-280 CFA / kg, depending on the moisture content, with higher prices being paid for dried bark. However, the price paid at roadside to the local collectors vary from 75 CFA (paid to pygmies who supply fresh bark along the Kribi-Campo road) to 150 CFA to Bulu suppliers at Bivoumba, who dry the bark over meat-drying racks. Recently, the President of the North-West Traditional Healers Association, Chief Fomentum, was asked to supply large quantities of bark to a contractor, to sell on to Plantecam, for 50 CFA / kilo for P. johimbe and 75 CFA / kilo for Prunus africana. Clearly, the profit-margin for the contractors is high and local people are not receiving a fair price for their work. However, none of the local collectors interviewed were aware of the true price of the bark and thought it worthwhile to collect bark to supply the contractors.

P. johimbe bark exploitation is a seasonal activity as the yohimbine levels are highest during the rainy season (Paris and Letouzey, 1960). During the months of May - September, the contractors travel into the areas where P. johimbe is known to occur, contacting villagers to exploit the bark directly and promise to return subsequently with transport and payment in two to three weeks. The majority of the contractors have been operating in the same regions for a number of years and use the same local exploiters.

The principles guiding the so-called sustainable exploitation of bark that have been applied to Prunus africana, i.e. removal of opposite two quarters of bark and then subsequent removal, years later, of the other two quarters, have not been applied to P. johimbe. The bark exploited is often collected from the main stem only (except when the bark is harvested by pygmy exploiters - see below) and not the branches. This is surprising, given that yohimbine occurs in not only both the branches and young stems, but also in the leaves. Often, to increase outputs, the trees are felled and Plantecam themselves admit that during exploitation "..98% of the trees exploited are probably felled" (Nkuinkeu, pers. comm.). According to the majority of informants interviewed, the trees can be harvested when they are around 10cm dbh. Although all stated that it was easier and more economic to harvest from larger diameter trees, these individuals were not so commonly found.

In the field it was explained to us that whilst the P. johimbe trees callused well after a small amount of bark removal3, removal of large quantities of bark led to an attack by a stem borer which penetrated the unprotected stem, killing the tree. That is why many harvesters preferred to fell the tree, as "the tree would die anyway" (Bivina, pers. comm.). Bakola (pygmy) harvesters, who were commonly employed to harvest yohimbe all along the Edea - Campo road, not only fell the trees but cross-cut them into portable pieces. The bark was removed from the cut logs, carried to the roadside and sold. All the bark from the tree is removed, including that of the branches. The remaining logs were then used for fuelwood (Mana, pers. comm.).

3.2. Impacts of exploitation

Despite current levels of exploitation, P. johimbe presently has a healthy recruitment and there does not seem to be a problem with regeneration. However, these data are rather deceiving as, although the current regenerative capacity of the species is not yet compromised, removal through felling of reproductive individuals especially at current rates of exploitation in certain areas will ultimately affect future regenerative potential (i.e. less seed trees = less seedlings = reduced recruitment = less future harvestable trees).

4. Confusion between P. johimbe and P. macroceras

Henry (1939), in a study of Pausinystalia johimbe and related species concluded that P. macroceras contains a number of alkaloids, especially large quantities of the inactive alkaloid yohimbinine, which led to P. macroceras being named "false yohimbe" (Small and Adams, 1922). Yohimbine itself is present in P. macroceras, although in very small quantities. Despite this low concentration of yohimbine, P. macroceras bark is widely used as an aphrodisiac throughout its range, especially where P. johimbe does not occur (Motte, 1980; author pers. obs.) and it seems the two are used correspondingly as part of local health care strategies (ibid.).

In the field, the two species are reputedly distinguished through slash characters. Yohimbine becomes yellow-orange-brown on exposure to light. P. johimbe oxidises red-brown very slowly and P. macroceras oxidising rapidly. However, in the field it is clear that this character is not reliable. With the bark and bole characteristics of both species being highly similar, the two species are almost impossible to tell apart using slash characters. The confusion between the species is not helped by the fact that the two species appear to be highly allopatric, meaning that direct comparison in the field is not often possible. However, the leaves of both species are highly distinctive with P. johimbe having sessile, obovate leaves 15-25 cm long, often in whorls of three with distinctive cordate leaf bases, while P. macroceras has petiolate, ovoid leaves 6-15 cm long.

More subtle differences between the two species include the fact that the bark of P. johimbe is extremely bitter to the taste and easy to peel, whilst P. macroceras bark is less bitter and is extremely difficult to peel, often needing beating first to loosen the cambial layer from the sapwood. Interestingly, Plantecam suggested that all P. johimbe bark needed to be beaten before being removed. However, our field work did not suggest this was the case and, with all of the P. johimbe trees we collected samples from, the bark peeled extremely easily.

Interestingly, of all the different cultural groups interviewed, only one, the Bulu, distinguished between P. johimbe and P. macroceras, with the former named "crocodile" and the latter "caiman". The remaining groups, the Fang, Bassa, Bali, Beti, Baka and Bakola did not differentiate between the two species stating that the bark of both have corresponding uses. Even though the Bulu distinguish between the two species, they use the bark of each for the same purpose. Indeed our informant assured us that there was no difference in the effects of bark treatment from each species (Bivina pers. comm.). In addition, it is claimed that P. macroceras bark is harvested more often because it is more common.

Given the field evidence and, given that some bark supplied to Plantecam is known to have an extremely low yohimbine content, there can be no doubt that a good proportion (ca. 60-70%) of the bark received by Plantecam is that of P. macroceras, which is known to have very low levels and very poor quality yohimbine. With a simple field guide prepared for collectors, it would be a simple task to ensure that all bark received is P. johimbe which would both conserve the resource (individual trees of P. macroceras) whilst ensuring profitability (gaining higher concentrations of the desired alkaloids from the processed bark).

5. Implications for management and sustainability

5.1. Potential for domestication

Due to the destructive harvesting methods employed and the rapidly-growing market for aphrodisiac remedies, ICRAF have begun a research programme to investigate the potential of P. johimbe for domestication and inclusion into their agroforestry systems programme.

One of the greatest dilemmas with initiating a domestication programme for any forest product is whether to begin work that could provide material for a hypothetical future market that could no longer exist when the products reach maturity. In contrast, one could decide that the volatile nature of such markets makes the investment prone to risk and no action is taken inevitably leading to the extirpation of the species. In the case of P. johimbe, as for Prunus africana, along with the obvious biological urgency, the market seems secure enough in the short-medium term to warrant the development of cultivated systems. If the market no longer exists in the long-term, the species can be used for other purposes such as fuelwood, aside from serving a valuable ecological function.

Table 2: Diagnostic bark characters of P. johimbe and P. macroceras (modified from Small and Adams, 1922).


P. johimbe

P. macroceras

Macroscopic characters





Outer surface



Grey to reddish-brown

Light or dark brown


Longitudinal furrows; many transverse cracks, 1-2cm apart

Often scraped; longitudinal furrows and ridges; few or curved transverse cracks


Grey or white; few or many

Grey, usually numerous


Thin or thick, often easily detached

Thin, adhering closely

Inner surface




Dark-brown or reddish-brown


Finely striated and ridged

Ridged and wrinkled


Short, fibrous, sometimes splintery on inside, surfaces soft, velvety

Same as P. johimbe

Microscopic characters




Width of cork

1/20 to 1/3

1/4 to 2/3

Width of cortex (No of cells)




Grey to dark brown

Dark brown



No of cells wide




Yellowish grey to reddish brown

Same as P. johimbe



Width of cortex

1/16 to 1/1

1/6 to 1/1


Yellowish brown to reddish brown

Same as P. johimbe

Medullary rays


TS inner bast width

1-4 cells

1-3 cells




TS outer bast width

1-3 cells

1-3 cells


Diverging, cells elongating tangentially

Curving irregularly, cells elongate tangentially


Straight or curved

Often distorted, curved

LS tangential width

1-3 cells

1-3 cells


6-35 cells

5-20 cells


Narrow spindle or rectangular

Somewhat rectangular with slightly tapering ends

LS radial depth

8-30 cells

5-20 cells

Bast fibres



Usually in one-cell wide rows, 1-3 occur "beaded", no "twinning" in outer bast

Radial rows 2-3 cells wide common but not "beaded"; "twinning" in outer bast







Shape TS



Shape LS

Long spindle, pointed ends

Spindle with sharply pointed ends


Punctiform or sometime linear

Linear or sometime punctiform


Thick, not striated

Thick, not striated

5.2. Vegetative propagation

The stumps of felled damaged individuals of P. johimbe are known to coppice well from the point of breakage and these new shoots are often both healthy and prolific. This ability to produce shoots is a positive indication that a great deal of clonal propagation material can be obtained from a few well-selected stock plants and initial vegetative propagation trials have been extremely positive (Tchoundjeu et al., in press).

Figure 3. Coppice shoots of Pausinystalia johimbe (Photo: T. Sunderland).

5.3. Seed propagation

The seeds of P. johimbe are orthodox. Such seed is often able to lay dormant in the soil seed bank for some time and germinate only when the red/far red light ratios change, notably when more direct light can penetrate the forest floor. Seed collection and germination tests have indicated that seed propagation is possible, but the young seedlings are prone to "damping off"; a fungal disease that attacks the newly emerged cotyledons. Further research into the optimum methods of seed propagation is continuing.

5.4. In-situ management

Whilst it is of course important to initiate a domestication programme for a potentially threatened species such as P. johimbe, it is also essential that this is implemented alongside a rational forest management regime. The ecology of P. johimbe (fast-growing, reproductively gregarious, light demanding) suggests that, with further work on the potential sustainability of bark harvesting from standing trees, a reasonable assessment could be made regarding the quantities that could be harvested from standing forest.

In addition, it is also essential that local communities benefit from the exploitation of a resource such as yohimbe. In Cameroon, and soon in Gabon and Equatorial Guinea, the moves towards Community Management of forest resources with a view to sustainability should ensure that the communities managing such resources not only benefit from their exploitation, but are also paid a fair price for the resource. This is not the case at present. P. johimbe could undoubtedly provide a good case study for the equitable and sustainable management of such high-value forest products.


The authors would like to thank Anacletus Koufani, Augustin Njiamnshi, Crisantos Obama and Dinga Njingum Franklin for their diligent contributions to this study in the field.


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Personal communications (Cameroon unless otherwise indicated)

Francois Xavier Bivina, Traditional Healer, Bivoumba Village, South Province.

Chief Fomentum, President of NW Association of Traditional Healers, Bali.

Dr John Fordip, Traditional Healer, Bali, NW Province.

Mana, Bakola hunter, Lolabe, South Province.

Robert Nkuinkeu, Botanist, Plantecam, SW Province.

Ntole Antoine, Traditional Healer, Eseka, South Province.

James Okala, Hunter, Alouma, South Province.

Ba Aloysius Sah, Traditional Healer, Bali, NW Province.

Dr John Vaughan, Diabetes Specialist, Royal Sussex County Hospital, UK.

3 A sample of this bark was collected to determine the amount and quality of yohimbine, the results of which have implications for potential sustainable management of wild populations.

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