Unsustainable harvesting of Prunus africana tree threatens treatment of prostate disorders

 As rates of prostate disorders spiral upwards, new research pinpoints where to grow this dwindling African source of alternative medicine

NAIROBI (28 March 2012) Responding to the dwindling abundance of Prunus africana in the wild, a tree listed as “vulnerable to extinction” by the International Union for Conservation of Nature, a recent study by the World Agroforestry Centre identifies possible locations in Kenya for developing tree farms.

The United Nations Food and Agriculture Organization (FAO) reported as far back as 1996 that the demand for the species’ bark, which is used to produce treatments for prostate gland disorders, could lead to its over-exploitation.

“Extracts that can help alleviate some prostate disorders are in high demand,” said Peter Gachie, a lead scientist working with the World Agroforestry Centre. “The Prunus africana tree, a primary source of medicine, has become threatened as a result. Without the conservation of high yielding populations, these trees could be harvested to extinction. This will have a negative effect on the economic livelihoods of smallholder farmers and narrow the options for those suffering from prostate disorders.”

According to the World Agroforestry study published in the January-March 2012 issue of the journal Forests, Trees and Livelihoods, cultivating the tree on farms will alleviate the threat of extinction caused by unsustainable wild harvests. The study also determined how old and large the tree should be to maximize the harvest of the tree’s bark.

The first step of tree domestication is identification of superior or desired germplasm. In the study, crude bark extracts from different forest zones in Kenya were compared to determine the zones with superior germplasm, those with high yields of crude extract and the best chemical composition, which provided the locations with the best sources of planting material.

“A higher yielding tree will add to the rural farmer’s income,” says Peter Gachie. “The Prunus africana is commonly used in households as a treatment for a variety of ailments but its market potential is yet to be realized.  In future, when more research is available, the benefits of this tree will be better appreciated by all people involved in the value chain.”

Prostate-related diseases increase in prevalence as men age.  And as the average age of the world’s population increases, the incidences of prostate diseases will increase as well, triggering a corresponding rise in demand for therapies.    

According to the World Cancer Research Fund International, prostate cancer is the second most common cancer in men worldwide. Around 910,000 cases of prostate cancer were recorded in 2008, accounting for approximately 14 percent of all new cancer cases in men. It is predicted that the number of cases will almost double (1.7 million) by 2030.

Prunus africana is an evergreen tree 10-40m in height, with a stem diameter of up to 1m. It has a black/brown, rugged bark, heavy, shiny foliage and small white or greenish flowers. Bark extracts from the tree have been used to treat prostate disorders in men, both traditionally and in modern medicine. In 1980 200 metric tonnes of Prunus africanabark was harvested primarily for this purpose, and by 1997 the demand had risen to approximately 3500 tonnes and has been growing steadily ever since.

The tree is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), which only allows for licensed trade of products from the tree. However, several of the countries that are party to CITES have been unable to monitor trade in Prunus africana products due to lack of resources.

Earlier research conducted by the Centre revealed that it takes 12-15 years to produce the bark that contains the active ingredient for the remedy for prostrate disorders. The current study reveals that mid-sized trees between 30-50cm diameter at breast height (dbh) and mainly 40-55 years old give the best yields of this valuable extract.

The study by Gachie’s team focused mainly on species that are found in natural forests in Kenya because they were assumed to be the trees’ true origin. They compared bark extracts from five different forest zones in Kenya namely Timboroa, Eburu, Kinale, Kakamega and Kobujoi. Trees from Timboroa had the highest extract yields while Kakamega and Kinale samples had the highest number of compounds. The species is a highland forest tree that can also be found on the slopes of Mt Kenya, Mt Elgon, Cherengani hills, the Aberdares and Mau ranges. Previous research examining Prunus africana populations in Madagascar, Democratic Republic of Congo (DRC), Cameroon and Kenya found that Kenya’s population of Prunus africana also have the highest concentration of active ingredients.

“Kenya’s populations need to be collected, conserved, and domesticated as soon as possible,” Gachie adds. “Public and commercial tree breeders and companies have an opportunity to integrate as many qualities from differentPrunus africana populations as possible to improve the quality of the medicinal extract.”

 “This study could be a step to creating a database of high yielding Prunus africana trees,” he concludes.

The World Agroforestry Centre is doing its part in preserving these trees and shrubs by holding samples of most of the species with medicinal qualities in its gene bank, researching and growing these trees in plant nurseries at its headquarters in Nairobi, as well as encouraging their cultivation and conservation on farms and landscapes. The Centre’s gene bank holds close to 200 species.

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CLICK HERE for more information on domestication of various agroforestry trees 

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Yvonne Otieno at +254 722 4295

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