HO CHI MINH CITY, Vietnam — In 1990, Nguyen Thi Ngoc Tram learned of a rare herb that for centuries was used to treat royal family members in the imperial capital of Hue.

HO CHI MINH CITY, Vietnam — In 1990, Nguyen Thi Ngoc Tram learned of a rare herb that for centuries was used to treat royal family members in the imperial capital of Hue.

Known as "the king's herb," the plant was believed to ease symptoms associated with prostate problems and menopause. "This was medicine for the emperors," said Nguyen, who first heard about it while chatting with a street-side tea vendor. "It was a secret. The doctors were not allowed to talk about it."

Nguyen devoted 15 years to developing the plant, officially known as Crinum latifolium, into an herbal medicine.

Vietnam, inaccessible to Western scientists for decades because of wars, is now considered fertile ground for plant research in an era when Americans are increasingly open to nontraditional medicines. Scientists from the United States are descending on the Southeast Asian country, known as a bio hot spot with some 12,000 plant species. And investors are looking to back products such as Crinum latifolium — also called Crila.

"It's one of the most diverse areas of the world," Djaja Djendoel Soejarto, a professor in the College of Pharmacy at the University of Illinois at Chicago, said of Southeast Asia. He splits his time between the United States and Vietnam, where he studies plants and how they were traditionally used to treat illnesses.

"It is believed that a plant that is part of folklore, used for thousands of years by a population, must have something in it," he said. "Many plants in Vietnam have been used to treat diseases. The potential for developing new medicines — that is our interest."

Vietnam has a deep history of relying on plants for remedies. According to Vietnamese tradition, Tue Tinh, the 14th-century founder of Vietnamese traditional medicine, was sent to China to treat the wife of an emperor to keep the country's powerful neighbor from invading.

Today, Soejarto, working with Vietnamese scientists, has discovered chemical compounds new to science that he hopes may someday lead to new ways to treat diseases such as malaria and cancer.

What makes relatively undeveloped Asian countries such as Vietnam important in the natural-remedies field is that "a lot of traditional knowledge is still preserved," said Ikhlas Khan, assistant director of the National Center for Natural Products Research at the University of Mississippi, which recently began collaborating with Vietnam's Academy of Science and Technology. "This is a good time for them to pay attention to their inheritance."

Khan, however, said Western scientific research needs to be applied to these traditional remedies to ensure they are safe to be consumed over a long period. "They can be dangerous."

While he has not studied Crila, Khan believes Nguyen and her researchers "know what they are doing."

There have never been bad side effects, Nguyen said.

"Some men say it even increases their sexual function," she added.

Dr. Michael Scott, an obstetrics gynecologist in Atlanta, recently visited Nguyen's labs while on a medical charity mission and decided to conduct clinical trials of the herb to see if it is effective in treating women with uterine fibroid tumors, the most common noncancerous tumors in women of childbearing age. He believes Crila could be another treatment physicians can offer patients without the negative side effects common in many expensive pharmaceuticals.

Scientists have a long track record discovering plants that can be used in modern medicine. A chemical compound discovered during the 1800s in the bark of a South American plant that natives used in blow guns to stun animals, for instance, was eventually developed into anesthesia for surgery.

In the early 1990s, the National Center for Complementary and Alternative Medicine, which supports scientific examination of plants for medicinal purposes, was established.

"As the health care system has become more expensive, as people see more diseases — more obesity, more diabetes — they are taking more interest in their health, and that includes natural medicine," said Tori Hudson, a clinical professor at the National College of Naturopathic Medicine in Portland, who is conducting a study of Crila's effect on menopausal symptoms.

In 2010, dietary supplements in the United States produced a $28.1 billion industry — up 63 percent from $17.2 billion in 2000, according to the Nutrition Business Journal. In 2010, herbs and plants represented 18 percent of that market.

Crila has been on the market in Vietnam in pill form since 2005 and has been used by 300,000 Vietnamese, said Sue McKinney, a Mendocino, Calif.-based entrepreneur who is distributing the herbal pill in the United States. Those who use the herb say it reduces prostate problems, such as frequent or painful urination, and eases menopausal symptoms — hot flashes, night sweats, mood swings.

Years before Nguyen developed Crila into a commercial product, Vietnamese-Americans brought the herb back to places such as Silicon Valley, said McKinney, a Santa Clara University School of Law graduate who splits her time between Northern California and Vietnam. But it wasn't until late 2010 that Crila was sold in the United States in pill form. She said she is in discussions with other investors, including some from Silicon Valley, interested in backing her Crila distribution company, Crinum Health.

Santa Cruz resident Ralph Neate became an investor after he took Crila to alleviate symptoms from an enlarged prostate. "If I drank some iced tea, by the time I finished, I was running to the bathroom," said Neate, 68. He also had a hard time sleeping through the night because of repeated trips to the bathroom. Now, he said, he sleeps through the night.

Nguyen, a short and serious woman, is considered one of her country's premier scientists. Her father was a famous ecologist in Vietnam and Nguyen's grandfather once discovered a treatment for snake bites after observing a rat survive a poisonous snake bite by eating wild grass and pushing it into its wound.

Nguyen, 62, oversees two large plantations and a factory that produces Crila in an undeveloped agricultural region north of Ho Chi Minh City. Her plants, which produce a lilylike flower from bulbs, take years to achieve maturity. Her entire operation, Nguyen said, is organic, down to the fertilizer from cows that have only been fed organic food.

"This works on Vietnamese people," she said. "So it will work on American people. A prostate is a prostate."