Agroforestree Database

Local names:
 English (johimbe), Trade name (yohimbe), Yoruba (idagbon)

Pausinystalia johimbe is a tree 9-30 m tall; with ternate vegetative and generative ramification, rarely decussate. Bark usually occurs in channeled pieces, 4-10 mm, thick with a varying tinge of red in the grey-brown or brown outer and inner surfaces. The outer surface is longitudinally furrowed and bears numerous narrow, transverse cracks at fairly regular intervals of 1-2 cm.

Leaves with petiole up to 5 mm long; blades 24-47 x 10-17.5 cm glabrous, obovate, cuneate or rounded, sometimes angustate or cordate at the base, acumen less than 5 mm long; (8-)13-18 pairs of prominent secondary nerves and reticulate intersecondary nerves; domatia, if present, glabrous intermediate between crypt- and pit type.

Inflorescence terminal or axillary, 10-21(-10) cm long and 9-15 cm wide; stipules at the base persistent. Flowers (4-)5-merous. Calyx outside densely hairy, inside with many long hairs.

Capsule almost 100% septicidal and somewhat loculicidal, 1-1.5 x 0.6 cm. Seeds 8-12 x 1.8-2.5 mm. 

P. johimbe is closely related to P. macroceras (K. Schum.) Pierre and historically they have been exploited for the same purpose. The species are easily distinguished through slash characters. The difference being that P. johimbe oxidizes red-brown very slowly and P. macroceras oxidizes very rapidly.

Ecology

Occurs mostly in the Atlantic evergreen forest with Caesalpiniaceae, an extensive forest formation extending from S.E. Nigeria to Congo. The species occurs mainly in closed canopy forest. Most common in coastal forest, although not widespread throughout its range. Endemic to its region.

Native range
Cameroon, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon, Nigeria

Tree management

A fast growing tree but never reaches great diameter, with the maximum being around 50 cm dbh. The species coppices well, producing strong, highly phototrophic shoots, and would be an ideal candidate for a clonal propagation programme once desirable phenotypes have been identified. 
The bark is used to extract yohimbine; the main stem gives the best material but is not rich in alkaloids until the tree is 15-20 years of age when it can contain 2-15%. Bark exploitation is a seasonal activity as the yohimbine levels highest during the rainy season.

Produces prolific quantities of seed, the characteristics of which indicate that it might lend itself to long-term storage.

Occurs mostly in the Atlantic evergreen forest with Caesalpiniaceae, an extensive forest formation extending from S.E. Nigeria to Congo. The species occurs mainly in closed canopy forest. Most common in coastal forest, although not widespread throughout its range. Endemic to its region.

Although the seed and seedlings need light for their development, they cannot survive in full sun and desiccate and die rapidly. The older stems (>3 m high or 5 cm dbh), however, are able to grow and reproduce in high light situations lending themselves to inclusion in both agroforestry and monoculture systems. Natural regeneration is good. For seed collection, the optimum period for fieldwork in both Cameroon and Equatorial Guinea would be between November-January.

Poison:  Poisonous doses of yohimbe are reported to paralyze respiration and the drug can cause severe hypotension, abdominal distress and weakness. It can also be used as an ichthytoxicant (fish poison).

A preferred fuelwood species.

Fibre:  The inner bark is utilized as straps for hunting panniers.

Timber:  The young poles are used for construction purposes. The species is widely used as a snare-trap mechanism due to its flexibility.

Tannin or dyestuff:  The bark contains tannins.

Medicine:  The bark contains up to 6% of a mixture of alkaloids, the principle one being yohimbine, which is also known as aphrodine, quebrachine or corynine. The presence and amount of alkaloid activity in P. johimbe bark is highly variable. P. johimbe, is the source of the only clinically-proven cure for impotence and has long been used as a traditional stimulant in Africa. Both the crude drug and yohimbine have a long history of use as aphrodisiacs in Western medicine in both prescription and herbal markets. Yohimbe is symatolytic and hypotensive and has a local anaesthetic action similar to that of cocaine but it is not mydriatic. The vasodilating action of yohimbe is particularly strong on the sex organs, hence its aphrodisiac action. P. johimbe is also used as a local anaesthetic, a mild stimulant to prevent drowsiness, a hallucinogen, a treatment for angina, a hypotensive, a general tonic, a performance enhancer for athletes, a remedy to increase the clarity of the voices of singers during long festivals and as a treatment to increase the resilience of hunting dogs. Yohimbine-related products have also been widely used as a vetinerary medicine for the promotion of sexual proclivity amongst stud animals. Remedies are taken in two forms: powder (ground bark) and liquid (bark boiled in water).

Intercropping:  Because P. johimbe is a middle-story tree, it has the potential to be an ideal species for farmers to grow in their fields in agroforestry systems.