Commonly known as spanish needle or beggar's ticks, Bidens pilosa is a common crop weed and wasteland plant widespread on every continent except Antarctica. Easily recognizable by the sharp, aggravating seed pods that embed themselves into hair and clothing, Bidens pilosa is used in both traditional Chinese medicine and Western herbalism as well as in folk medical traditions around the world. Each of these traditions employs the herb for a number of different applications, including the treatment for common colds, influenza, bacterial infections, inflammatory conditions, hepatitis and urinary tract infection. Although the subject of substantial phytochemical research, the use of Bidens pilosa for the prevention or treatment of any disease has not been evaluated by the United States Food and Drug Administration as of 2011.
While Western herbalists generally see the herb in terms of its detoxifying, anti-inflammatory, hepatoprotective, antipathogenic and urogenital tonifying properties, traditional Chinese medical doctors understand the herb in different terms. Bidens pilosa is considered to be useful in clearing superficial heat, dispersing stagnation, invigorating the blood, removing damp wind, clearing damp heat from the lower triple burner, and purging elemental fire from the body. These conditions correlate to specific medical conditions, but they do not neatly conform the Western ideas of health and illness.
Much of the research into the possible medical applications of Bidens pilosa has focused on the pharmacological activity of just a few of its chemical constituents. Bidens pilosa is rich in a class of anti-pathogenic chemicals know as the polyacetylenes. Among these is phenylheptatriyne, which in some studies has been found to inhibit cytomegalovirus as well as gram-positive bacteria in general. Aliphatic acetylenes has been found to inhibit the growth of Plasmodium falciparum, the microbe responsible for malaria infections. Although phenyheptatriyne and the other polyacetylenes are believed to be photoactivated, they have not been found to cause damage to genetic material like the photoactivated furanocoumarin toxins.
The flavonoids present in Bidens pilos have also shown some promise as anti-inflammatory agents. This activity is thought to be mediated through their interference with prostaglandin-synthesis, likely through the inhibition of cyclooxygenase (COX) enzymes. Friedelin and friedelan-3 beta-ol are the plant's most potent anti-inflammatory flavonoids, while phenylheptatriyne is the most effective of its polyacetylenes.
Whole plant extracts of Bidens pilosa have also been found to exhibit strong antioxidant and liver protecting properties. The same extract has been found to lower blood pressure in rats, potentially through its vasodilating activity. A similar animal study also found that rats given Bidens pilosa had lower levels of blood platelet aggretation and a reduced risk of thrombosis.