Banaba Leaf Extract (Corosolic Acid)
Updated September 19, 2026 · By Theo Marchetti
The Short Answer
Banaba (Lagerstroemia speciosa) is a tropical plant whose leaf extract, standardized to corosolic acid and ellagitannins, has shown promising results for glycemic control in preliminary studies. A 2025 narrative review highlighted its potential alongside chromium picolinate for prediabetes management. However, the evidence base is earlier-stage than ingredients like berberine or chromium — consisting primarily of small studies, animal models, and in vitro work. Clinical doses of corosolic acid range from 16 to 48 mg per day, requiring substantial extract amounts at typical 1–2% standardization.
What is Banaba Leaf Extract (Corosolic Acid)?
Banaba (Lagerstroemia speciosa) is a tropical tree native to Southeast Asia, India, and the Philippines. Its leaves have been used in traditional medicine — particularly in the Philippines — as a remedy for high blood sugar and kidney conditions. The primary bioactive compound is corosolic acid, a pentacyclic triterpene, along with ellagitannins (including lagerstroemin) and other triterpenoids. Standardized extracts are typically characterized by their corosolic acid content, commonly 1–2%. Banaba extract is available as capsules, tablets, and tea preparations.
How it works
Corosolic acid's primary proposed mechanism involves activation of glucose transporter proteins (GLUT4), facilitating glucose uptake into cells independent of insulin — a mechanism distinct from but complementary to insulin-dependent pathways. Ellagitannins (particularly lagerstroemin) may inhibit alpha-glucosidase and alpha-amylase, reducing carbohydrate digestion and postprandial glucose spikes. Early research suggests corosolic acid may also decrease blood sugar levels through multiple mechanisms studied across animal models, human subjects, and in vitro systems.
What the evidence says
Banaba's evidence base is promising but early-stage. Most published research consists of small human trials, animal studies, and in vitro work. There are no large-scale randomized controlled trials or comprehensive meta-analyses specifically evaluating banaba extract for metabolic outcomes.
- Banaba leaf extract, rich in corosolic acid and ellagitannins, has shown promising results in improving glycemic control in a prediabetes context. — A 2025 narrative review exploring nutraceutical solutions for prediabetes, evaluating the effects of banaba and chromium picolinate individually and in combination. (2025 narrative review)
- Corosolic acid has been reported to decrease blood sugar levels through multiple mechanisms in animal models, human subjects, and in vitro systems. — A review examining the management of diabetes and its complications with banaba (Lagerstroemia speciosa L.) and corosolic acid across multiple study types. (Stohs et al. (2012), Pharmacognosy Research)
Effective dosage
Published studies have used corosolic acid at doses of 16–48 mg per day. At a typical 2% standardization, delivering 16 mg of corosolic acid requires 800 mg of extract — and 48 mg requires 2,400 mg. This has significant implications for proprietary blends: a 276 mg blend containing six ingredients could allocate at most ~46 mg of banaba extract, yielding approximately 0.9 mg of corosolic acid at 2% standardization — roughly 18–53 times below the studied dose range.
Some studies have used whole banaba leaf preparations at higher volumes, but the active compound delivery per gram of raw material is lower than concentrated extracts.
Safety and interactions
Banaba extract is generally well tolerated in published studies and traditional use. No serious adverse effects have been reported at standard doses. The most commonly noted concern is the potential for hypoglycemia when combined with glucose-lowering medications or other blood-sugar-supporting supplements (chromium, berberine, cinnamon).
Drug interactions: individuals taking insulin, metformin, or other antidiabetic medications should consult a healthcare provider before adding banaba extract, as the combined glucose-lowering effect could cause blood sugar to drop too low.
Safety data in pregnancy and breastfeeding is insufficient — avoidance is recommended.