''Strophanthus kombe'', the kombe arrow poison, is a

vine A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners themselv ...

that grows in the

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

regions of Eastern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

, and is part of the genus ''Strophanthus'', which contains approximately 38 species. ''S. kombe'' contains a

cardiac glycoside Cardiac glycosides are a class of organic compounds that increase the output force of the heart and decrease its rate of contractions by inhibiting the cellular sodium-potassium ATPase pump. Their beneficial medical uses are as treatments for co ...

which directly affects the

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

. Historically, both the seeds and roots of the plant were used in the preparation of poison

arrowhead An arrowhead or point is the usually sharpened and hardened tip of an arrow, which contributes a majority of the projectile mass and is responsible for impacting and penetrating a target, as well as to fulfill some special purposes such as sign ...

s used for hunting. Today, the seeds are used pharmaceutically for patients with certain heart conditions that affect blood circulation. The seeds are traded primarily with

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, but have also been exported to the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

and

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

Distribution

''Strophanthus kombe'' is found growing naturally in the tropical regions of southeast Africa. As it is not a commercially cultivated species, it principally occurs as wild plant. It is not typically seen growing outside of its native region, although specimens are sometimes collected from the wild to be grown in foreign

botanical garden A botanical garden or botanic gardenThe terms ''botanic'' and ''botanical'' and ''garden'' or ''gardens'' are used more-or-less interchangeably, although the word ''botanic'' is generally reserved for the earlier, more traditional gardens, an ...

Habitat and ecology

''Strophanthus kombe'' is usually found on an isolated hill known as a

monadnock An inselberg or monadnock () is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. In Southern Africa a similar formation of granite is known as a koppie, a ...

near water sources such as coastal forests,

gallery forest A gallery forest is one formed as a corridor along rivers or wetlands, projecting into landscapes that are otherwise only sparsely treed such as savannas, grasslands, or deserts. The gallery forest maintains a more temperate microclimate above th ...

riparian A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...

thickets and

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

s. It is typically found at altitudes ranging from sea level to 1100m. It is usually found growing as vines in the forests between the coast and center of Africa.

Morphology

''Strophanthus kombe'' is a

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

vine, that under solitary conditions can be found as a

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

. Most frequently, it occurs as a climbing vine that grows to the highest points on tall trees. It is seen curling on the ground and draping from tree to tree. It can grow up to 3.5 meters, with a stem that grows up to 10 cm in diameter. The bark is a reddish brown, with dark brown, grey or black

lenticel A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a ...

s. The roots are thick and fleshy. The papery leaves are simple, and found in opposite arrangement. The young leaves are exceptionally hairy on both sides, but as they age, the top of the leaves become smooth. One to twelve cream colored flowers can be found on the peduncle. They are narrowly ovate or linear and slightly unequal. The dichasial cyme inflorescence is on the terminal end of the plant.

Flowers and fruits

The flower of ''Strophanthus kombe'' is an inflorescent, bisexual, fragrant flower. It is cream colored, yellow at the base with red spots and streaks inside. There is a thick layer of hair on the outside towards the top, while the inside of the flower has very few hairs. The

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filame ...

of the flower is found near the base of the corolla tube. The

pistil Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils'' ...

contains a

style Style is a manner of doing or presenting things and may refer to: * Architectural style, the features that make a building or structure historically identifiable * Design, the process of creating something * Fashion, a prevailing mode of clothing ...

a few millimeters in length, with a ring-like head surrounding a minuscule stigma. The fruit of the flower contains two follicles that narrow towards the apex and end in a knob of various sizes. It has two thick and hard-walled compartments containing many spindle shaped seeds.

Medicinal

''Strophanthus kombe'' is known for its historical use as a source of arrow poison. Today it is used medicinally to treat heart failure. The plant has been used for two extremes, ending a life and saving a life, so proper dosage is crucial when using this plant medicinally. Cardiac glycosides extracted from the seeds reduce the heart rate but increase the force and efficiency of the contractions. Some glycosides can also be found in the roots and flowers. A mixture of glycosides known as ''strophanthin-k'' is found in the seeds. The purified compound is a white crystalline powder that is water-soluble and liable to hydrolysis under warm acidic conditions. Precursors for a semi-synthetic compound known as ''acetylstrophanthidin'' are found within the seeds of ''Strophanthus kombe''. When used clinically, this compound provides a rapid onset of vascular stimulant action.

Trivia

This plant was inadvertently used as a medical experiment by

Sir John Kirk Sir John Kirk, (19 December 1832 – 15 January 1922) was a physician, naturalist, companion to explorer David Livingstone, and British administrator in Zanzibar, where he was instrumental in ending the slave trade in that country, with the a ...

, a nineteenth-century plant explorer who brought back specimens of ''Strophanthus kombe'' for the Royal Botanic Garden at Kew,

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

. Some of the plant’s juice accidentally found its way onto his toothbrush. After brushing his teeth, he reported a quick drop in heart rate.