The natural chemicals, called kukoamines, also selectively affect a chemotherapeutic target for trypanosomes and similar diseases such as sleeping sickness, said the team from the Institute of Food Research (IFR).
Kukoamines and related compounds were found at higher levels than some other compounds in potatoes that have a long history of scientific investigation.
However, the chemicals are not yet well researched and have only previously been found in an exotic plant (Lycium chinense) whose bark is used to make an infusion in Chinese herbal medicine.
The researchers still do not know how stable the compounds are during cooking and must conduct detailed dose-response studies to discover how they affect our health.
Yet the unexpected findings, published in yesterday's issue of the Journal of Agricultural and Food Chemistry (vol 53, issue 13, pp5461-6), revealed the benefits of a new type of research - metabolomics.
Metabolomics is the science of analysing the diversity of small molecules produced by an organism in relation to genome function and to other properties of interest, such as nutritional status and disease.
Scientists used to have to know what they were looking for when analysing composition, targeting 30 or so known compounds. With new metabolomic techniques, they can find the unexpected by analysing hundreds or even thousands of small molecules produced by an organism.
"Only a small proportion of plants have been subjected to serious phytochemical analysis," said food scientist Dr Fred Mellon. "Until now, none of the new metabolites we found in this study had ever been identified from any of the species we examined, and only one had ever been described from another plant source."
"No-one had expected to find them in one of the staple food crops of the Western world," he added.
Potatoes have been cultivated for thousands of years and were considered to be well understood.
"But this surprise finding shows that even the most familiar of foods might conceal a hoard of health-promoting chemicals," added Dr Mellon.
IFR has recently acquired a £600,000 spectrometer to be used for metabolomics studies. It allows complex mixtures of small molecules to be analysed at high resolution and the chemical structures of unknown compounds to be determined.
The new instrument, shared with the John Innes centre, is expected to make a major contribution to a wide range of research projects in the fields of diet and health, food-safety microbiology and plant and microbial science.