“The Pride of India” owns its name
A botanical traditionally used in Southeast Asia for diabetes and its related complications is Lagerstroemia speciosa, also known as Banaba. This tree is common to the region and has been a part of Philippine local herbal medicine and other medical traditions such as Ayurveda for many years.
Corosolic acid, one of the primary active compounds found in its leaves, is what extracts from the Banaba tree are typically standardized to. However, substances known as gallotannins and ellagitannins, which are also found in the extract, may mediate the observed biological effects as well, giving importance for use of the whole herb in addition to corosolic acid.[1],[2] Although clinical trials have focused on the role of the extracts in blood sugar regulation, results in cellular and animal models suggest that they also may be protective against obesity,[3] elevated uric acid levels,[4] high cholesterol,[5] hypertension, and liver and kidney damage[6],[7] – each of these being issues that often accompany diabetes and metabolic syndrome.
Banaba and glucose homeostasis
Cellular, animal, and human studies reinforce Banaba’s value in promoting healthy blood sugar levels. One mechanism via which the compounds within L. speciosa may reduce blood sugar levels is by increasing glucose uptake into cells where it can be used.[8],[9] Animal studies have shown that Banaba extracts also inhibit alpha-amylase and alpha-glucosidases (enzymes that play a role in starch digestion) thereby reducing the absorption of carbohydrates that are eaten during a meal.[10] As such, its benefits are greatest when it can be taken prior to meals to promote this additional effect.
Animal studies have shown that Banaba extracts also inhibit alpha-amylase and alpha-glucosidases (enzymes that play a role in starch digestion) thereby reducing the absorption of carbohydrates that are eaten during a meal.
In humans, these effects and possibly others have been shown to have a dose-dependent impact on blood glucose levels. In one clinical study involving both healthy individuals and those with diabetes, corosolic acid was shown to significantly reduce post-challenge blood glucose levels.[11] In another study involving type 2 diabetics, daily supplementation with Banaba extract standardized to 1 percent corosolic acid (providing 0.48 mg of corosolic acid) significantly reduced fasting blood sugar levels by 30% after two weeks.[12] The individuals in this study were not on other medications and had initial fasting blood glucose levels of 140 – 250 mg/dL.
Corosolic acid also protected against diabetic kidney damage in animals, reducing levels of protein found in the urine as well as lowering serum creatinine and blood urea nitrogen (BUN) values.
In genetically diabetic mice, a lowering effect was seen not only with blood glucose, but hemoglobin A1C (HbA1c) levels were also significantly diminished.[3],[13] Corosolic acid also protected against diabetic kidney damage in animals, reducing levels of protein found in the urine as well as lowering serum creatinine and blood urea nitrogen (BUN) values – each being markers of kidney damage.[14] On a cellular level, proliferation of glomerular cells and glomerular fibrosis (both typically seen in diabetes-related renal damage) were also diminished via treatment with corosolic acid.
Summary
Collectively, the available evidence suggests this botanical may broadly address the issues related to diabetes, with benefits extending beyond improved glucose control. Taken alone or in combination with other directed botanicals (such as berberine or other Ayurvedic herbs), the standardized extracts from the Banaba tree provide another option for the increasingly common issue of type 2 diabetes.
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