Pygeum africanum Hook.f.
Prunus africana, or red stinkwood , is an evergreen tree native to the montane regions of sub-Saharan Africa and the islands of Madagascar, Sao Tome, Fernando Po, and Grande Comore at about 900–3400 m above sea level. The mature tree is 10–25 m high, open-branched, and often pendulous in forest, shorter and with a round crown of 10–20 m diameter in grassland. It requires a moist climate, 900–3400 mm annual rainfall, and is moderately frost-tolerant.
The bark is black to brown, corrugated or fissured, and scaly, fissuring in a characteristic rectangular pattern. The leaves are alternate, simple, long (8–20 cm.), elliptical, bluntly or acutely pointed, glabrous, and dark green above, pale green below, with mildly serrated margins. A central vein is depressed on top, prominent on the bottom. The 2-cm petiole is pink or red. The flowers are androgynous, 10-20 stamens, insect-pollinated, 3–8 cm., greenish white or buff, and are distributed in 70-mm axillary racemes. The plant flowers October through May. The fruit is red to brown, 7–13 mm, wider than long, two-lobed, with a seed in each lobe. It grows in bunches ripening September through November, several months after pollination.
The fruit is too bitter to be of interest to man; however, it is a favored food supply for many animals, which spread the seeds. Dian Fossey reports of the mountain gorilla: "The northwestern slopes of Visoke offered several ridges of Pygeum africanum .... The fruits of this tree are highly favored by gorillas." East African Mammals reports that stands of Pygeum are the habitat of the rare Carruther's mountain squirrel and asserts, "This forest type tends to have a rather broken canopy with many trees smothered in climbers and dense tangles of undergrowth."
It is currently protected under appendix II of CITES and in South Africa under the National Forest Act (Act 84) of 1998.
Traditionally, the parts are used for fevers, malaria, wound dressing, arrow poison, stomach pain, purgative, kidney disease, appetite stimulant, gonorrhoea, and insanity.
An extract, Pygeum, an herbal remedy prepared from the bark of P. africana, is used as an alternative medicine in patients with benign prostatic hyperplasia.  It has shown positive results in in vitro studies and mouse models of prostate cancer. A handful of clinical trials have been conducted to investigate the effectiveness of Pygeum in treating benign prostatic hyperplasia. The trial studies were done comparing P. Africanum to a placebo, not a pharmaceutical drug. These researchers found that there was an improvement in patients’ symptoms after taking an extract of P. Africanum compared to placebo. Several of the studies that were analyzed used a standardized extract of the P. Africanum. The outcomes evaluated included urine flow, the number of times an individual had to urinate at night as well as urinary retention. These were all reduced in the patients that took part in the clinical trials. Therefore, a standardized extract of P. Africanum does seem to have clinical importance in reducing the symptoms of BPH. Stomach upset including nausea and abdominal pain were reported as side effects, but overall this herb was well tolerated.
However, it is important to note that not all researchers agree that P. Africanum has clinical significance. Some believe that the doses used in the clinical trials were too high and therefore might not be practical to use in a clinical setting. Additionally, some of the studies that show advantages of P. Africanum in BPH did not meet certain guideline criteria.  An explanation of the exact ingredients of the extract that make it effective as well as the actual pathway of how Pygeum reliefs BPH symptoms are some of the guidelines that were not described in some clinical trials. There are no known interactions between P. Africanum with other medicines, food, herbal supplements or disease.
The collection of mature bark for this purpose and for other medical uses has resulted in the species becoming endangered. P. africana continues to be taken from the wild. Plantecam Medicam deserves credit for attempting sustainable bark harvesting by removing opposing quarters of trunk bark rather than girdling the trees. However, quotas have been awarded by the Forestry Department without adequate forest inventories due to some harvesters, spurred on by the high prices, removing too much of the bark in an unsustainable manner. In the 1990s, an estimated 35,000 debarked trees were being processed annually. The growing demand for the bark has led to the cultivation of the tree for its medicinal uses.
The timber is a hardwood employed in the manufacture of axe and hoe handles, utensils, wagons, floors, chopping blocks, carving, bridge decks, and furniture. The wood is tough, heavy, straight-grained, and pink, with a pungent bitter-almond smell when first cut, turning mahogony and odorless later.
Discovery and classification
The name of the remedy, pygeum, comes from the name of the plant, which was discovered to botany by Gustav Mann during his now-famous first European exploration of the Cameroon Range, with Richard Francis Burton and Alfred Saker, in 1861. A letter from Mann to the Linnean Society of London, read by William Jackson Hooker, then Director of the Royal Botanic Gardens, Kew, on June 5, 1862, describes the naming of the peaks of the Cameroon Range (such as Mount Victoria, later Mount Cameroon) and the collection of specimens there. The latter were shipped back to Kew for classification, which was duly performed by Hooker and his son, Joseph Dalton Hooker, who had the responsibility of publishing them, as William died in 1865.
When the publication came out the Hookers had named the plant Pygeum africanum, followed by the designation "n. sp.", an abbreviation for nova species. The habitat is listed as "Cameroons Mountains, alt. 7000-7500 feet", which was above the tropical forest and in the alpine grasslands. Hooker notes that another specimen had been "gathered in tropical Eastern Africa" at 3000 feet by Dr. Kirk on an expedition of David Livingstone.
The first publication of the synonym in 1864 had been preceded by publication of the bare name in 1863 in a book by Richard Francis Burton. Evidently Hooker had already made the contents of J. Proc. Linn. Soc., Bot. 7 for 1864 available to some, as Burton mentions the volume and Mann's letter in 1863.
Hooker gives scant hint of why he chose "pygeum"; however, what he does say indicates it was common knowledge among botanists. Kirk's specimen fruit was "a much depressed sphere". By this, he undoubtedly meant to reference Joseph Gaertner's genus, Pygeum Gaertn., which innovates pygeum from a Greek word, πυγή, "rump, buttock", because the two lobes of the fruit resemble the human gluteus maximus muscles.
In 1965, Cornelis Kalkman moved Pygeum to Prunus, and this classification has the authority for now. However, a recent cladistic study notes of Pygeum: "its relationships to Prunus remain to be tested by molecular cladistics."
In addition to red stinkwood, Prunus africana is known by the common names iron wood, stinkwood, African plum, African prune, African cherry, and bitter almond. In other languages spoken where it grows, it is known as tikur inchet in Amharic, mkonde-konde in Chagga, muiri in Kikuyu, entasesa or ngwabuzito in Ganda, uMkakase in Xhosa, inyazangoma-elimnyama or umdumezulu in Zulu, and rooi-stinkhout in Afrikaans.
A 1994/1995 study published in 1997 by Marchant and Taylor did a pollen analysis on and radiocarbon-dated two core samples from montane Mubindi Swamp in Uganda. The swamp is a catchment at 2100 m altitude between mountain ridges. It is a "moist lower montane forest" in Bwindi Forest National Park. The investigators found montane Prunus, represented by currently growing P. africana, has been in the catchment continuously since their Pollen Zone MB6.1, dated about 43000-33000 years ago.
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- Edgar, AD; Levin, R; Constantinou, CE; Denis, L (2007). "A critical review of the pharmacology of the plant extract of Pygeum africanum in the treatment of LUTS". Neurourology and urodynamics 26 (4): 458–63; discussion 464. doi:10.1002/nau.20136. PMID 17397059.
- Shenouda NS. Sakla MS. Newton LG. Besch-Williford C. Greenberg NM. MacDonald RS. Lubahn DB."Phytosterol Pygeum africanum regulates prostate cancer in vitro and in vivo." Endocrine. 31(1):72-81, 2007 Feb.
- Medicinal plants on verge of extinction – environment – 10 January 2009 – New Scientist
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- The British names did not survive the transfer of Cameroon to Germany in 1884 and now are nearly unknown.
- Hooker, Sir W.J. (1864). "Letter from Mr. G. Mann, Government Botanist, describing his Expedition to the Cameroon Mountains". Botanical Journal of the Linnean Society VII: pages 1–13. doi:10.1111/j.1095-8312.1863.tb01054.x.
- Hooker, J.D. (1864). "On the Plants of the Temperate Regions of the Cameroons Mountains and Islands in the Bight of Benin; collected by Mr. Gustav Mann, Government Botanist". Botanical Journal of the Linnean Society VII: pages 191–192. doi:10.1111/j.1095-8312.1864.tb01067c.x. The article occupies pages 171–240. The botanical abbreviation for this publication is J. Proc. Linn. Soc., Bot.
- Hooker, J.D. (1863). "Enumeration of the Mountain Flowering Plants and Ferns Collected by M. Gustav Mann, Government Botanist, during his various ascents of the Cameroons Mountains, of Clarence Peak, Fernando Po, and of the Peak of San thomé". Abeokuta and the Camaroons Mountains: An Exploration: Appendix III. London: Tonsley Brothers. pp. 270–277.
- Page 47, first note.
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- See under De Fructibus et Seminibus Plantarum. The edition is the 1788.
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- Kalkman, Cornelis. "The Old World Species of Prunus subg. Laurocerasus including those formerly referred to as Pygeum". Blumea 13: 1–115. The specification is Blumea 13:33.
- Bortiri, Esteban; Oh, Sang-Hun; Gao, Fang-You; Potter, Dan (2002). "The Phylogenetic Utility Of Nucleotide Sequences Of SORBITOL 6-PHOSPHATE DEHYDROGENASE In Prunus (Rosaceae)". American Journal of Botany 89 (11): 1697–1708. doi:10.3732/ajb.89.10.1697.
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- Hall, J.B.; Sinclair, Fergus L; O'Brien, Eileen M. (2000). Prunus Africana – A Monograph. Bangor: University of Wales. ISBN 1-84220-048-8.
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- Dailey, Bryan W.; Fernandes, Erick C.M. "The Effect of Ecological Conditions on Density and Growth of Prunus africana Seedlings in Madagascar". Cornell University.
- WWF. "Prunus africana" (pdf).
- Prunus africana in West African plants – A Photo Guide.