Pentadiplandra

Pentadiplandra brazzeana is an evergreen shrub or liana that is the only species assigned to the genus Pentadiplandra, and has been placed in a family of its own called Pentadiplandraceae. 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 than saccharose.[3] Brazzein may be useful as a low-calorie sweetener, but is not yet allowed as a food additive in the United States and the European Union.

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]
  • Cercopetalum dasyanthum Gilg
  • Cotylonychia chevalieri Stapf
  • Pentadiplandra gossweileri Exell

Description

Pentadiplandra brazzeana is a monoecious shrub of maximally 5 m (16 ft), but can also develop into a liana, climbing up to 20 m (66 ft) high in the trees.[4][5] The shrub morph usually has a mass of branched bulging roots, while the liana morph has a large, fleshy tuber. The branches are without hair and carry alternately set, simple and entire leaves, without stipules at the base of the ½–1 cm (0.2–0.4 in) long leaf stalk.[4]

The hairless leaf blade is elliptical to oblanceolate, 5–15 cm (2.0–5.9 in) long and 1½–5 cm (0.6–2 in) wide, with a wedge-shaped base, a pointed tip, a dull or shining dark green upper surface and a dull dark green lower surface, and a central vein that branches feather-like into five to eleven pairs of side veins. The flowers are in racemes in the axils of the leaves or at the tip of the branches, with the common 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 or hermaphrodite, all on the same plant. They sit on a 1–2 cm (0.39–0.79 in) long stalk, and carry five elliptical to lanceolate, ½–1 cm (0.2-0.4 in) long, green sepals with a violet margin, which are slightly buiging and fused at their base. Inside are five free white to yellowish petals 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 (or androgynophore), which carries at its top ten to thirteen stamens with about 6 mm (0.24 in) long thin filaments connected only at the base forming two or three worls. The anthers 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 a gynophore, has (four or) five cavities and carries a short style topped by a (4– or) 5-lobed stigma. In male flowers the ovary is rudimentary, and in female flowers the stamens are rudimentary.

The fruit is a globe-shaped berry 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]

Phytochemistry

Pentadiplandra contains thiocarbamates such as methyl N-benzylthiocarbamate, methyl and ethyl N-methoxybenzylthiocarbamate, and glucosinolates such as benzyl- and 4-methoxybenzyl glucosinolates.[4] It has cells containing myrosinase.[5]

Taxonomy

Pentadiplandra brazzeana was first described by French botanist and physician Henri Ernest Baillon in 1886, who assigned it to the family Capparaceae, based on a specimen from Osika in Congo by Jacques de Brazza. In 1897, Ernest Friedrich Gilg described Cercopetalum dasyanthum in the Capparaceae.[7] Otto Stapf described Cotylonychia chevalieri in 1908 as part of the Sterculiaceae. In 2000, Clemens Bayer showed Cotylonychia to be synonymous to Pentadiplandra.[8] Arthur Wallis Exell introduced the name Pentadiplandra gossweileri in 1927.[9] The family Pentadiplandraceae was proposed by John Hutchinson and British botanist, physician and scientific explorer John McEwan Dalziel in the Flora of West Tropical Africa in 1928.[10]

Phylogeny

P. brazzeana is the only known species in the genus Pentadiplandra, and has been assigned its own family named Pentadiplandraceae. Analyses of the development of the flower and anatomic features suggest that Pentadiplandra is a relict genus branching off near the base of the core Brassicales. It has many characters in common with the American genus Tovaria. Current insights in the relationships of the Brassicaceae, based on a 2012 DNA-analysis, are summarized in the following tree.[11]

core Brassicales
 
 
 
 
 

family Resedaceae

 
 
 

family Gyrostemonaceae

 
 
 

family Pentadiplandraceae

 
 
 
 

family Tovariaceae

 
 
 

family Capparaceae

 
 
 

family Cleomaceae

 
 

family Brassicaceae

 
 
 
 
 
 

family Emblingiaceae

 
 

Etymology

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 worls of five stamens each.[12] brazzeana is probably derived from the name of the collector of the type specimen, J. de Brazza

Distribution and habitat

The plant grows in Angola, the Democratic Republic of the Congo, the Central African Republic, the Republic of the Congo, Cameroon, Gabon and Nigeria.[13] It is not uncommon in upland primary forest dominated by Scorodophloeus 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]

Sweetness and calories

Most primates have a genotype of the taste 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 few calories. Such proteins may imitate sweetness to lure wild animals to eat the berries and disperse the seeds. Western lowland gorillas (Gorilla gorilla), however, have two mutations in the TAS1R3 gene, and although its diet contains a high proportion of fruit, scientists have not witnessed gorillas consuming P. 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]

Uses

Traditional uses

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 the Congo Basin.[4]

The pulp of the berries is eaten by children, and is used as a sweetener in maize porridge.[4][18]

Modern uses

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 was generally 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]

References
  1. Angiosperm Phylogeny Group (2009). "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III" (PDF). Botanical Journal of the Linnean Society. 161 (2): 105–121. doi:10.1111/j.1095-8339.2009.00996.x. Retrieved 2013-07-06.
  2. "The Plant List: A Working List of All Plant Species". Retrieved 15 August 2015.
  3. Kant, R (2005). "Sweet proteins – Potential replacement for artificial low calorie sweeteners". Nutrition Journal. 4: 5. doi:10.1186/1475-2891-4-5. PMC 549512. PMID 15703077.
  4. "Pentadiplandra brazzeana Baill". PROTA4U. Retrieved 2017-07-27.
  5. C. Bayer; O. Appel (2003). "Pentadiplandraceae". In K. Kublitski; et al. (eds.). Flowering Plants: Dicotyledons. p. 329. doi:10.1007/978-3-662-07255-4_33. ISBN 978-3-642-07680-0.
  6. Byng, James W. (2014). The Flowering Plants Handbook: A practical guide to families and genera of the world. p. 317.
  7. "Cercopetalum dasyanthum". Tropicos.
  8. Bayer, Clemens (2000). "On the Identity of Cotylonychia Stapf (Sterculiaceae)". Kew Bulletin. 55 (2): 499–500. doi:10.2307/4115670. JSTOR 4115670.
  9. "Pentadiplandra gossweileri Exell". African Plant Database. Retrieved 2017-08-01.
  10. "Pentadiplandraceae Hutch. & Dalziel". Tropicos. Retrieved 2017-08-03.
  11. Su, Jun-Xia; Wang, Wei; Zhang, Li-Bing; Chen, Zhi-Duan (June 2012). "Phylogenetic placement of two enigmatic genera, Borthwickia and Stixis, based on molecular and pollen data, and the description of a new family of Brassicales, Borthwickiaceae" (PDF). Taxon. 61 (3): 601–611. doi:10.1002/tax.613009.
  12. Quattrocchi, Umberto (1999). CRC World Dictionary of Plant Names: Common Names, Scientific Names, Eponyms, Synonyms, and Etymology. 3. CRC Press. ISBN 978-0849326738.
  13. "Pentadiplandra brazzeana Baillon". Global Biodiversity Information Facility. Archived from the original on 2016-03-03. Retrieved 2017-07-29.
  14. Walters, D. E; Hellekant, G (2006). "Interactions of the Sweet Protein Brazzein with the Sweet Taste Receptor". Journal of Agricultural and Food Chemistry. 54 (26): 10129–10133. doi:10.1021/jf062359y. PMC 2527743. PMID 17177550.
  15. Assadi-Porter, F. M; Abildgaard, F; Blad, H; Cornilescu, C. C; Markley, J. L (2005). "Brazzein, a small, sweet protein: Effects of mutations on its structure, dynamics and functional properties". Chemical Senses. 30 Suppl 1: i90–1. doi:10.1093/chemse/bjh128. PMID 15738211.
  16. Gruber, Karl (13 July 2016). "Gorillas may have evolved a way to beat a cheating berry plant". New Scientist. Retrieved 27 September 2017.
  17. Guevara, E.E.; Veilleux, C.C.; Saltonstall, K.; Caccone, A.; Mundy, N.I.; Bradley, B.J. (2016). "Potential arms race in the coevolution of primates and angiosperms: brazzein sweet proteins and gorilla taste receptors". American Journal of Physical Anthropology. 161 (1): 181–185. doi:10.1002/ajpa.23046. PMID 27393125.
  18. Hladik, C.M.; Hladik, A. (1988). "Sucres et "faux sucres" de la forêt équatoriale: évolution et perception des produits sucrés par les populations forestières d'Afrique [Sugars and "false sugars" of the tropical forest: Evolution and perception of sweeted products by the forest people of Africa]". Journal d'Agriculture Tropicale et de Botanique Appliquée (in French). 35: 51–66. doi:10.3406/jatba.1988.6676.
  19. Ming, D.; Hellekant, G. (1994). "Brazzein, a new high-potency thermostable sweet protein from Pentadiplandra brazzeana". FEBS Letters. 355 (1): 106–108. doi:10.1016/0014-5793(94)01184-2. PMID 7957951. S2CID 6650703.
  20. Hills, Sarah (24 June 2008). "New sweetener to hit market hungry for alternatives". FoodNavigator-USA.com.
  21. Watson, Elaine (22 October 2012). "Beyond stevia: Will brazzein make the natural sweeteners premier league?". FoodNavigator-USA.com.
  22. Watson, Elaine (11 February 2014). "Brazzein entrepreneur seeks partner to take next-generation natural sweetener to market". FoodNavigator-USA.com.
  23. Turner, Jeanne (September 8, 2016). "Scientists make a sweet discovery: lab-synthesized brazzein". Food Dive.
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