Origin and geographic distribution
Bidens pilosa is a cosmopolitan weed, originating from South America and common in all tropical and subtropical areas of the world. In Africa Bidens pilosa is recorded as a weed in many countries and it is likely to occur in all countries, including the Indian Ocean islands. It is reported as a vegetable or potherb among others in Sierra Leone, Liberia, Côte d’ Ivoire, Benin, Nigeria, Cameroon, DR Congo, Kenya, Uganda, Tanzania, Malawi, Botswana, Zambia, Zimbabwe and Mozambique. Bidens pilosa is a weed in both field and plantation crops and is recorded as troublesome in about 30 crops in more than 40 countries, including about 20 African countries. It is considered one of the most noxious annual weeds in East Africa. It often becomes dominant after the eradication of perennial grasses, and displays allelopathic effects on a number of crops.
In sub-Saharan Africa, the fresh or dried tender shoots and young leaves are used as a leaf vegetable especially in times of food scarcity. It is an ingredient of sauces accompanying the staple food. The leaves are, fresh or after parboiling, dried in the sun and stored as powder for the dry season. In Uganda, the leaves are boiled in sour milk. Old leaves are not suitable for consumption because they have a bitter astringent taste.
Bidens pilosa is used as a medicinal plant in many regions of Africa, Asia and tropical America. Roots, leaves and seed have been reported to possess antibacterial, antidysenteric, anti-inflammatory, antimicrobial, antimalarial, diuretic, hepato-protective and hypotensive activities. In Uganda, five different medicinal uses are known: the sap from crushed leaves is used to speed up clotting of blood in fresh wounds; a leaf decoction is used for treating headache; sap from the plant is put in the ear to treat ear infection; a decoction of leaf powder is used to treat kidney problems; and a herbal tea made from the plant decreases flatulence. Extracts of Bidens pilosa are used in southern Africa to cure malaria. The Manyika people in the eastern highlands of Zimbabwe retain the first water used for cooking Bidens pilosa foliage for later use as a medicinal drink to cure stomach and mouth ulcers, diarrhoea, headaches and hangover. The Zulu in South Africa use a suspension of powdered leaves as an enema for abdominal trouble, whereas in Congo a concoction made from the whole plant is taken as a poison antidote, or to ease child delivery and to relieve the pain from hernia. In South Africa, strong decoctions of the leaf taken in large doses have been reported to be helpful in treating arthritis. In Côte d’Ivoire, the plant is used for treating jaundice and dysentery. The plant sap is applied to burns in Tanzania. In Nigeria, the powder or ash from the seed is used as a local anaesthetic and rubbed into cuts. The Giriama tribe from the coastal areas of Kenya use a leaf extract to treat swollen spleens in children. This tribe also uses a mixture of the dried and ground leaves of Bidens pilosa, soap and hot pepper as an insecticide for the control of leaf miners and other insects. The traditional application of Bidens pilosa in local medicine, especially for its antiseptic and anti-inflammatory properties, will remain of importance, the more so as the plants are readily available. The immunomodulatory, anti-inflammatory and especially antimalarial properties deserve further attention.
Spanish needles are been used in traditional medicine systems for infections of all kinds: from such upper respiratory tract infections as colds and flu to urinary tract infections and venereal diseases-and even infected wounds on the skin. Research has begun to confirm these uses in several in vitro microbial studies. In 1991, scientists in Egypt first documented Bidens pilosa antimicrobial activity against various pathogens. Other in vitro studies have demonstrated its antibacterial activity against a wide range of bacteria including Klebsiella pneumonia, Bacillus, Neisseria gonorrhea, Pseudomonas, Staphylococcus, and Salmonella. Extracts of the leaf also have been documented to have antimycobacterial activity towards Mycobacterium tuberculosis and M. smegmatis. A water extract of the leaf has shown significant anti-yeast activity towards Candida albicans. Much of Spanish needles antimicrobial actions have been attributed to a group of chemicals called polyacetylenes, which includes a chemical called phenylheptatriyne. Phenylheptatriyne has shown strong in vitro activity against numerous human and animal viruses, bacteria, fungi, and molds in very small amounts.
In the tropics, Bidens pilosa is also used for snakebite and malaria; research has confirmed these uses as well. Several studies have confirmed the plant's antimalarial activity; it reduced malaria in animals by 43-66 percent, and in vitro by 90%. With regard to its status as a traditional snakebite remedy, one research group confirmed that a Spanish needles extract could protect mice from lethal injections of neurotoxic snake venom.
Other research has focused on Bidens pilosa's anticancerous characteristics. Early research, in various in vitro assay systems designed to predict antitumor activity, indicated positive results in the early 1990s. Spanish needles first was reported to have antileukemic actions in 1995. Then researchers from Taiwan reported (in 2001) that a simple hot-water extract of Spanish needles could inhibit the growth of five strains of human and mouse leukemia at less than 200 mcg per ml in vitro.
In Nanyuki, Kenya, Bidens pilosa is collected for the extraction of natural dyes. Among the Efe of the DR Congo the root is washed and dried, then used as a painting brush. Livestock browses on the plants and in South Africa Bidens pilosa has been used as a fodder for pigs. However, dairy cattle are discouraged from browsing on it because the aromatic oil present in the plant has an objectionable smell that can taint milk. Chicken feed on the seed. In Uganda and in Mexico, the leaves are used as an invigorating or stimulant substitute for tea; while in the Philippines the flowers are used in the preparation of a kind of wine. The flowers are a good source of nectar for honeybees.Properties
Extracts of Bidens pilosa show antimalarial activity both in vitro and in vivo. The crude ethanol extract (50 μg/ml) causes up to 90% inhibition of Plasmodium falciparum growth in vitro, compared with 86–94% inhibition for the chloroform fraction and 68–79% for the butanol fraction (both at 50 μg/ml). In vivo the crude ethanol extract and the chloroform fraction cause about 40% reduction of Plasmodium berghei parasitaemia in mice. Phenylacetylenes and flavonoids have been found in the ethanol extract from the leaves and the roots. The results indicate that the antimalarial activity of Bidens pilosa may be attributed to the presence of acetylene compounds. The direct therapeutic usefulness of these compounds seems limited, since they are easily oxidized by air and light.
Polyacetylenes also have antimicrobial activity. A number of polyacetylenes extracts of Bidens pilosa are toxic to yeasts and some bacteria. This compound is an active anti-parasitic. Consumption of the leaves, as in South Africa, has been found to promote the development of oesophageal cancer, and dried leaves of Bidens pilosa have a co-carcinogenic action for oesophageal tumours induced in rats. In addition to the acetylenes, other compounds such as phytosterols (β-sitosterol), triterpenes and caffeic acid(s) are also reported from Bidens pilosa. The main flavonoids from leaf extracts are aurones and chalcones. Several flavonoids have anti-inflammatory properties, their detection in extracts from Bidens pilosa, together with the presence of the described acetylenes, may explain the use of Bidens pilosa in traditional medicine, especially for treating wounds, against inflammations and against bacterial infections of the gastrointestinal tract.
The ethanolic extract of Bidens pilosa showed a high inhibition of prostaglandin synthesis in an in vitro assay for cyclo-oxygenase inhibitors. The methanol extract showed radiation-protection activity for bone marrow. In addition, other pharmacological activity such as, antihyperglycaemic, immunomodulator, anti-ulcer and hypotensive activity were reported.
Mvere, B., 2004. Bidens pilosa L. Record from Protabase. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands.
3. Tropical Plant Database, Dbase File for Bidens Pilosa L., "The Healing Power of Herbs", Rainforest Nutrition;