| Pentadiplandra | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Brassicales |
| Family: | Pentadiplandraceae Hutch. &Dalziel[1] |
| Genus: | Pentadiplandra Baill. |
| Species: | P. brazzeana |
| Binomial name | |
| Pentadiplandra brazzeana | |
| Synonyms[2] | |
| |
Pentadiplandra brazzeana, also known asoubli, is an evergreen shrub or liana that is the only species assigned to the genusPentadiplandra, and has been placed in a family of its own calledPentadiplandraceae. It produces large red berries, sometimes mottled with grey. It is known from West-Central Tropical Africa, between northern Angola, eastern Nigeria and western Democratic Republic of Congo. The berry is sweet in taste due to the protein,brazzein, which is substantially sweeter thansaccharose.[3] Brazzein may be useful as a low-caloriesweetener, but is not yet allowed as a food additive in the United States and the European Union.
Pentadiplandra brazzeana is amonoecious shrub of maximally 5 m (16 ft), but can also develop into aliana, climbing up to 20 m (66 ft) high in the trees.[4][5] The shrubmorph usually has a mass of branched bulging roots, while the liana morph has a large, fleshy tuber. The branches are without hair and carryalternately set, simple and entire leaves, withoutstipules at the base of the ½–1 cm (0.2–0.4 in) longleaf stalk.[4]
The hairless leaf blade iselliptical tooblanceolate, 5–15 cm (2.0–5.9 in) long and 1½–5 cm (0.6–2 in) wide, with awedge-shaped base, a pointed tip, a dull or shining dark green upper surface and a dull dark green lower surface, and a centralvein thatbranches feather-like into five to eleven pairs of side veins. The flowers are inracemes in the axils of the leaves or at the tip of the branches, with thecommon inflorescence stalk much longer in terminal racemes, up to 16 cm (6.3 in) long.[4] The individual flowers can be functionally only male, only female orhermaphrodite, all on the same plant. They sit on a 1–2 cm (0.39–0.79 in) longstalk, and carry five elliptical tolanceolate, ½–1 cm (0.2-0.4 in) long, greensepals with a violet margin, which are slightly buiging and fused at their base. Inside are five free white to yellowishpetals of between 2 and 2½ cm (0.8–1.0 in) long, set between the neighboring sepals. They consist of a separate, wide, pouch-like base or alternatively described as having a conspicuous scale, fringed by hairs that form a "roof" over a chamber and also make the base of the sepals cling together. The petal further consists of a lanceolate to oblanceolate plate, with irregular burgundy-colored splashing, and a pointy tip.[4] Stamens and pistol are separated from the sepals and petals by a firm stalk (orandrogynophore), which carries at its top ten to thirteenstamens with about 6 mm (0.24 in) long thinfilaments connected only at the base forming two or three whorls. Theanthers on top are attached at the base, have two cavities that release pollen by lengthwise slits. The ovary, which may be clearly distanced from the base of the stamens by agynophore, has (four or) five cavities and carries a shortstyle topped by a (4– or) 5-lobedstigma. In male flowers theovary is rudimentary, and in female flowers the stamens are rudimentary.
The fruit is a globe-shapedberry of 3½–5 cm (1.4–2 in) in diameter, entirely red or mottled with grey, containing many seeds attached to the axis surrounded by pink pulp.[4] The seeds are kidney-shaped, and have an outer layer of wooly, white, one-celled hairs.[6]
Pentadiplandra containsthiocarbamates such as methyl N-benzylthiocarbamate, methyl and ethyl N-methoxybenzylthiocarbamate, andglucosinolates such as benzyl- and 4-methoxybenzyl glucosinolates.[4] It has cells containingmyrosinase.[5]
Pentadiplandra brazzeana was first described by French botanist and physicianHenri Ernest Baillon in 1886, who assigned it to the family Capparaceae, based on a specimen fromOsika in Congo byJacques de Brazza. In 1897,Ernest Friedrich Gilg describedCercopetalum dasyanthum in the Capparaceae.[7]Otto Stapf describedCotylonychia chevalieri in 1908 as part of theSterculiaceae. In 2000,Clemens Bayer showedCotylonychia to besynonymous toPentadiplandra.[8]Arthur Wallis Exell introduced the namePentadiplandra gossweileri in 1927.[9] The family Pentadiplandraceae was proposed byJohn Hutchinson and British botanist, physician and scientific explorerJohn McEwan Dalziel in theFlora of West Tropical Africa in 1928.[10]
P. brazzeana is the only known species in the genusPentadiplandra, and has been assigned its own family named Pentadiplandraceae. Analyses of the development of the flower and anatomic features suggest thatPentadiplandra is arelict genus branching off near the base of the coreBrassicales. It has many characters in common with the American genusTovaria. Current insights in the relationships of the Brassicaceae, based on a 2012 DNA-analysis, are summarized in the following tree.[11]
| core Brassicales |
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Pentadiplandra is the contraction of the Greek words πέντε (pente), meaning "five", διπλόος (diploos), "double", and ἀνδρὸς (andros), "male" or "stamen", a reference to the usually two whorls of five stamens each.[12]brazzeana is probably derived from the name of the collector of the type specimen, J. de Brazza
The plant grows inAngola, theDemocratic Republic of the Congo, theCentral African Republic, theRepublic of the Congo,Cameroon,Gabon andNigeria.[13] It is not uncommon in upland primary forest dominated byScorodophloeus zenkeri, but also occurs regularly on the banks of rivers and in secondary forest. The species is found in particular in forest margins bordering savanna's in Cameroon. It does not appear in clusters anywhere.[4]
Most primates have agenotype of thetaste receptor protein,taste receptor type 1 member 3 (TAS1R3), that enables them to taste the protein,brazzein.[14][15] To humans, the fruit is intensely sweet, but provides fewcalories. Such proteins may imitate sweetness to lure wild animals to eat the berries and disperse the seeds.Western lowland gorillas (Gorilla gorilla), however, have twomutations in the TAS1R3gene, and although its diet contains a high proportion of fruit, scientists have not witnessed gorillas consumingP. brazzeana berries.[16] If factual, this avoidance behavior and the taste gene mutations may indicate a counter-adaptation to deter gorillas from foraging for low-calorie foods.[17]
The berries, leaves, roots, and tubers of these plants have been used in local traditional culture. Roots hung in the house are thought to repel snakes.[4] Powdered root bark is an ingredient of "African whiskey in sachets", which is said to be cheap but dangerous. The root is said to be eaten occasionally as a vegetable.[18] A syrup made from the root is marketed throughout theCongo Basin.[4]
The pulp of the berries is eaten by children, and is used as a sweetener in maize porridge.[4][18]
Brazzein has been isolated from the plant[19] and a company was formed to bring it to market in 2008, which initially said it would start selling the product by 2010 once it obtained agreement from the FDA that its brazzein wasgenerally recognized as safe (GRAS).[20] In 2012 the company said that regulatory approval might take an additional one or two years[21] and in 2014 it still had not obtained a GRAS waiver from the FDA and was seeking partners,[22] and the product was still not on the market as of 2016.[23]
