Known to herbalists for its healing powers, the native Hawaiian noni plant has been found to kill the bacterium that causes tuberculosis. The finding could lead to new drugs to fight the disease, according to research presented here during the 2000 International Chemical Congress of Pacific Basin Societies. Tuberculosis has resurfaced recently due to the emergence of drug-resistant strains, and is particularly prevalent in Hawaii.

The weeklong scientific meeting, held once every five years, is hosted by the American Chemical Society, in conjunction with its counterparts in Australia, Canada, Japan and New Zealand.

Noni, also known as Indian mulberry or its scientific name, Morinda citrifolia, is an evergreen plant that is recognized by its foul-smelling, green-skinned fruit. It is found throughout the world, particularly in Asia and northern Australia. Hawaii is the major source of noni in the United States.

While traditional Hawaiian healers have long used the plant to treat patients afflicted with tuberculosis (TB), this study represents the first report identifying the compounds that may be responsible for this action, according to researchers at the University of Santo Tomas (UST), Manila, Philippines.

The researchers randomly screened a group of native plants for potential activity against Mycobacterium tuberculosis, the bacterium that causes TB. In laboratory tests, a concentration of extracts from the leaves of the noni showed a significant inhibitory rate, killing 89 percent of the pathogens, they say. This compares favourably with rifampicin, a drug commonly used to treat TB, which has an inhibition rate of 97 percent at the same concentration, according to the researchers.

The active compounds were isolated from the extract and found to be phytosterols (plant steroids). The compounds are structurally different from those drugs that are typically used to treat TB, indicating that the compounds may act under a different mechanism that could be useful for building an alternative drug to fight resistant bacterial strains, the researchers say. An additional drug source could also provide cheaper alternatives to more expensive drugs for treating TB, they add.

"I hope that pharmaceutical companies will pay attention to this research and explore the noni plant as a potential source of drugs," says Jonel Saludes, who was the lead researcher on the study.

Like other herbal remedies, the curative powers of noni remain largely unproven, while its potential health risks are unknown. Still, the plant has become the target of a growing number of studies.

The incidence of tuberculosis is increasing worldwide, due largely to the emergence of drug- resistant bacteria. In 1999, Hawaii had the highest rate of TB in the nation, according to the Centers for Disease Control and Prevention. Unless improved efforts are undertaken to stem the growing threat worldwide, the disease will continue to rise, health officials warn.

More than 8,000 research papers will be presented during this year's International Chemical Congress, which is sponsored jointly by the American Chemical Society, the Chemical Society of Japan, the Canadian Society of Chemistry, the Royal Australian Chemical Institute and the New Zealand Institute of Chemistry.

Jonel Saludes is an assistant professor in the department of chemistry at the University of San Agustin in Iloilo City, Philippines.

The study was funded by the Philippine government, the International Foundation for Science, and the United Nations Educational, Scientific and Cultural Organization (UNESCO).