Chronic Antihyperglycemic Effect Exerted by Traditional Extracts of Three Mexican Medicinal Plants.

The short version

This 42-day study in laboratory rats tested three plants long used in Mexican traditional medicine for diabetes: Ageratina petiolaris, Calea urticifolia, and Eryngium cymosum. Type 2 diabetes (a condition where the body cannot properly regulate blood sugar) causes 90-95% of diabetes cases and is a leading cause of death in Mexico, where many people, especially in rural communities with limited access to health services, drink these plants as traditional teas alongside or instead of prescribed medication. The researchers wanted to know whether the plants' previously documented short-term blood-sugar-lowering effects would hold up over six weeks of continuous use. Six groups of six rats each were given hyperglycemia (high blood sugar) through a standard chemical induction method, then treated once daily for 42 days with one of: a placebo, a combination of two standard diabetes drugs (metformin and glibenclamide) as a positive comparison, or the traditional-strength tea extract of one of the three plants. A separate untreated, non-hyperglycemic group served as a healthy baseline. Researchers tracked blood glucose weekly, a longer-term blood sugar marker called HbA1c three times over the study, and blood fat (triglyceride) levels every two weeks. Rats given no treatment for their high blood sugar got steadily worse across the study. Ageratina petiolaris lowered blood glucose by 33% from its own starting point (a statistically meaningful reduction, p=0.0281), kept the HbA1c rise to just 2.63 percentage points versus roughly 10 points in the untreated group (p=0.0303), and was the only plant extract to also significantly reduce blood triglycerides (p=0.0031). Calea urticifolia and Eryngium cymosum did not significantly lower overall blood glucose compared to the untreated group, but they did significantly limit the HbA1c rise to about 2.4-3.0 percentage points each (both p=0.0156) - meaning that even without a clear glucose-lowering signal, both plants measurably slowed the longer-term worsening of blood sugar control. Neither of these two plants meaningfully affected triglycerides. The study's authors suggest chlorogenic acid, found in all three plants, may explain their shared blood-sugar effects, while a different compound unique to Ageratina petiolaris may explain its additional benefit for triglycerides. This is animal, not human, research, and the study did not examine pancreatic tissue, insulin levels, or the specific fat particles that matter most for heart-disease risk. The findings support these plants as promising candidates for further development but do not establish that the same doses would work the same way in people.

Key findings

• In rats with chemically induced high blood sugar, daily traditional-dose Ageratina petiolaris extract for 42 days reduced blood glucose by 33% and limited the rise in HbA1c (a marker of longer-term blood sugar control) to 2.63 percentage points, versus roughly 10 points in untreated animals.
• Ageratina petiolaris was the only one of the three plants tested that also significantly reduced blood triglycerides (a type of blood fat), an effect the authors attribute to a compound called L-chiro-inositol.
• Calea urticifolia and Eryngium cymosum did not significantly lower overall blood glucose compared with untreated animals, but both significantly limited the rise in HbA1c, meaning they slowed the worsening of blood sugar control over time even without a clear glucose-lowering effect.
• All three plants are already used as traditional teas by diabetic patients in Mexico, and this is the first study to test whether their previously documented short-term blood-sugar effects hold up over six weeks of continuous use.
• This is animal research in rats, not a human clinical trial, so the doses and effects seen here have not yet been confirmed in people with diabetes.

Common questions