Lagerstroemia speciosa, known as Banaba, Giant Crape-myrtle, and Pride of India, is a flowering tree. It is valued as an ornamental tree in tropical regions for its vibrant blossoms. It also has a long history in traditional medicine.
Botanical Description and Habitat
This medium-sized tree typically reaches heights between 15 and 45 meters, featuring a bole that can be straight or somewhat crooked. Its bark is smooth, often light gray, becoming mottled or papery as it matures. The leaves are simple, opposite, lanceolate, elliptic, or ovate, dark green and up to 20 centimeters long.
The tree produces large, showy flowers, usually borne in prominent terminal panicles. These blossoms display crinkled petals in shades ranging from white to pink, purple, or mauve. Following flowering, the tree develops round, woody, brown capsules containing numerous tiny, winged seeds.
Lagerstroemia speciosa is native to Southeast Asia, including the Philippines, India, Myanmar, Thailand, Malaysia, and Sri Lanka. It thrives in low to medium altitudes within open habitats, disturbed or secondary forests, and along riverbanks. It prefers well-drained, fertile soils but tolerates occasional flooding.
Key Bioactive Compounds
Interest in Lagerstroemia speciosa stems from its diverse bioactive compounds. The most studied is corosolic acid, a pentacyclic triterpene. This compound influences glucose metabolism, specifically by enhancing glucose uptake into cells.
Beyond corosolic acid, the leaves also contain ellagitannins, such as lagerstroemin, flosin B, and casuarinin. These compounds contribute to the plant’s biological activities, including stimulating insulin-like glucose uptake. Other constituents include ellagic acid, gallic acid, various flavonoids like kaempferol and quercetin, and other triterpenes and glycosides.
Traditional and Modern Health Applications
For centuries, Lagerstroemia speciosa has been used in traditional medicine to manage blood sugar levels. Corosolic acid decreases blood sugar levels, partly by facilitating glucose entry into cells. It may also reduce sucrose breakdown in the small intestine, further influencing glucose absorption.
Ellagitannins, including lagerstroemin, increase glucose uptake in fat cells, contributing to glucose-regulating effects. The plant influences glucose metabolism through multiple pathways, including reducing the body’s glucose production. Lagerstroemia speciosa also possesses antioxidant properties, with extracts demonstrating activity against free radicals. Some research suggests a role in weight management, potentially by reducing body weight and liver triglyceride content, and inhibiting fat cell differentiation.
Forms, Usage, and Safety Considerations
Lagerstroemia speciosa is available in various forms. These include teas made from dried leaves, powdered leaf capsules, and standardized extracts, often concentrated for specific amounts of active compounds like corosolic acid. Traditionally, it has been consumed as a decoction. Studies have explored dosages such as 12 grams of leaf powder daily over 90 days, or standardized extracts at 32 mg to 48 mg daily.
While generally considered safe when consumed orally in appropriate amounts, important safety considerations exist. A primary concern is potential hypoglycemia (abnormally low blood sugar), especially for individuals taking diabetes medications. Other reported side effects are typically mild and may include stomach upset, nausea, or headaches. Individuals with existing health conditions or on medication should consult a healthcare professional before use.