A gardenia fruit extract used in Chinese medicine for centuries to treat adult onset diabetes is effective, scientists have found.
The chemical was taken from a form of gardenia
The US team found a chemical from the fruit blocks the action of an enzyme which stops the production of insulin.
The research, published in Cell Metabolism, could lead to new drugs, the scientists said.
Diabetes experts said the work was in its early stages, and recommended a healthy diet and exercise for patients.
Insulin is made in the pancreas, and stimulates cells to take up as much glucose as they need for energy, thereby regulating blood sugar levels.
But in people with diabetes, there is too little insulin, which causes blood sugar concentrations to rise.
The researchers from the Beth Israel Deaconess Medical Center and Harvard Medical School focused on an enzyme called uncoupling protein 2 (UCP2) which prevents insulin being produced.
The team wanted to find a way to block the enzyme's action.
One of the team, Chen-Yu Zhang, who was familiar with traditional Chinese medicine, suggested looking at the extract of fruits of Gardenia jasminoides Ellis.
The extract has been used in traditional Chinese Medicine to relieve the symptoms of Type 2 diabetes.
Tests on mice showed the extract blocked UCP2's action, and that a chemical called genipin was the active compound.
When genipin was added to pancreatic tissue in the lab, it also reversed faults linked to obesity and high glucose levels in insulin-producing cells.
The researchers said their findings may lead to the development of new drugs, which would offer a significant advance as there is currently no available therapy for diabetes which targets the underlying causes of disease in insulin-producing cells.
It may potentially increase the use of Gardenia extract itself, they said.
Dr Bradford Lowell, who led the study, added: "Genipin represents an extremely useful investigational tool for studying a number of aspects of UCP2 biology."
Roopinder Brar, a care advisor at Diabetes UK, said: "We welcome any research into a potential treatment for Type 2 diabetes.
"However, this study is still in its early stages but we look forward to further investigation.
"For the 1.8 million people diagnosed with Type 2 diabetes, we recommend a healthy, balanced diet and physical activity."