Mucuna pruriens is the scientific name of the velvet bean or cowitch plant, thus named for the intense itching produced by touching the plant's seed pods or foliage. While generally grown as a fodder plant for livestock, the seeds of the plant may be eaten if meticulously processed to remove the potent, pharmacologically active chemicals within it. Of these chemicals, the most potent is levodopa, or L-dopa, the phytochemical thought to be responsible for the aphrodisiac and anti-parkinsonian properties attributed to the herb. Levodopa alone is a prescription drug used to increase the level of dopamine in the brain, primarily for treating the symptoms of Parkinson's disease. It is this powerful activity in the brain that led to the plant's use as a treatment for depression and movement disorders in Ayurvedic medicine as well as Siddha medicine for over 1,000 years.
The parts of the plant that are considered to be the most pharmacologically active are the seeds and hairs. Many formulations used in alternative medicine that make use of Mucuna pruriens employ a concentrated ethanolic extract of the plant, dramatically reducing the amount of plant matter that must be consumed to be physiologically active. The sale of a total extraction of Mucuna pruriens' active ingredient may, however, require a prescription in some countries, as it is pharmacologically identical to a prescription medication. By increasing the levels of the neurotransmitter dopamine in the brain, Mucuna pruriens may help reduce the frequency or severity of some of the symptoms of Parkinson's disease, such as muscular weakness, rigidity, tremor, slowing of voluntary movements, depression, and the decline of cognitive function. The same mechanism of action is likely to be responsible for its traditional use as a libido enhancer in both men and women.
In addition to its action as a direct precursor to the neurotransmitter dopamine, Mucuna pruriens is unusually rich in a number of nutrients, including magnesium, calcium, iron, manganese, phosphorous, zinc and copper. It is possible that these or some other compound within the plant may be responsible for the findings from a study that indicate Mucuna pruriens may lower blood sugar levels in diabetic patients. As of 2011 this study has yet to be replicated, however, and the finding must still be considered speculative.
Like the drug levodopa, Mucuna pruriens may produce side effects. These side effects are likely to be more pronounced when the herb is used in higher doses. Insomnia occurs in many users, while increased heart rate and body temperature occur infrequently.