The researchers -- Rainer Bussmann and Douglas Sharon -- traveled to Northern Peru to interview local healers known as curanderos and observe native healing practices. Bussmann and Sharon, who are both fluent in Spanish, also collected ethnobotanical information from plant sellers by purchasing native plants in local markets, and by accompanying curanderos on harvesting trips and to healing ceremonies.
Bussmann and Sharon collected Northern Peruvian plants from the wild and also purchased them from the markets, then took the specimens to curanderos to discuss medicinal properties and the plants' role in healing rituals.
The researchers were able to determine many of the plants' properties, including the season in which they are best grown, the region in which they are harvested and various ailments the plants have proven effective at treating.
Bussmann and Sharon were able to collect 510 plant species used by Northern Peruvian healers, as well as identify their traditional uses, vernacular names and various applications. The researchers found that the majority of treatments -- 207 -- were used for ritual or "magical" ailments, such as susto and espanto, a condition caused by fright brought on by a life event or the patient's environment.
Most of the researchers' plant discoveries were used to treat ritual or magical ailments, or were parts of hallucinogenic healing ceremonies. Common illnesses in Northern Peruvian regions include mal aire (bad air), mal viento (bad wind), mal ojo (evil eye) and envidia (envy). Such conditions are characterized by shock, poisoned food and changes in body temperature. Bussmann and Sharon characterized such illnesses in Western medical terms as "psychosomatic disorders," which are physical symptoms brought about from mental or emotional factors.
Ninety-five plants were used to treat respiratory disorders, which included common ailments such as cold, flu, bronchitis and asthma. According to Bussmann and Sharon, many such conditions could be brought on by damp living conditions that foster mold and insufficient air circulation.
The researchers found that 85 medicinal plants treated urinary tract problems, such as kidney stones and infections of the bladder or kidneys. For example, the plant Chanca Piedra, which translates to "Stonebreaker," is used to treat kidney stones, and has gained popularity in the international market.
Sixty-six of the plants battled infections of female organs, the researchers found. Uteran, ovarian, vaginal and post-partum infections were treated with 100 different applications of the plant species, while 39 additional uses helped women with childbirth, menstrual cramps and cycle regulation. A select few plants were involved in medicinal procedures for abortion, birth control and female fertility.
On the flip side, 52 plant species were used to treat "male" problems, including prostate inflammation, impotence, urination problems, fertility and hair loss. Twelve species served the dual purposes of impotence remedy and aphrodisiac.
Bussmann and Sharon said they believed that because only 61 plants were used to aid liver disorders, the curanderos were mainly employed to treat magical and ritualistic problems, such as mal aire.
"Disorders of internal organs fall far behind the most commonly treated medical conditions," they wrote. "This is another indication that curanderos in Northern Peru are to a large extent specializing in the treatment of psychosomatic disorders, and that 'bodily' illness are treated more as a sideline."
However, the researchers turned up 59 plant treatments for inflammation, such as that caused by tonsil and throat and infections. An additional 51 were used to treat stomach problems, while 45 aided in rheumatism treatment.
But perhaps the most interesting plant species utilized by the curanderos were those employed in cancer treatment. "The use of plant species in this field could provide particularly interesting leads in medicinal development," Bussmann and Sharon wrote.
Eighty-three percent of the plants the researchers collected were native Peruvian plants, and two-thirds were harvested and utilized fresh. Many of the plants were collected wild, and the most common applications included ingesting the herb or decoction, or applying the plants as poultices.
The Northern Peruvian curanderos typically used the leaves or the whole plant to create treatments. Medicinal flowers from the plants were used in roughly 10 percent of treatments, while seeds were used in 7 percent of remedies. The fruit, bark, peel or wood of healing plants were used in only a fraction of medicines.
According to Bussmann and Sharon's study conclusions, traditional Northern Peruvian curanderos have helped the region's centuries-old system of plant-based medicine survive, in spite of hundreds of years of suppression by Western medicine.
"Current research indicates that the composition of the local pharmacopoeia has changed since colonial times," the researchers wrote. "However, the overall number of medicinal plants employed seems to have increased. This indicates that the Northern Peruvian health tradition is still going strong, and that the healers and public are constantly experimenting with new remedies."
Though the ethnobotanical medical system of Northern Peru has survived thus far, Bussmann and Sharon warn that urban growth, climatic change, global interest in harvesting medicinal plants, and large-scale mining are serious threats to its future survival.