Queen's crape-myrtle

Queen’s crape-myrtle is a partly deciduous tree 10–20 m tall, occasionally to 25 m, usually branching low with a broad rounded crown; the bark is grey-brown, smooth and peels in large patches to reveal a paler, mottled fresh layer. The leaves are opposite, elliptic to oblong, 8–25 cm long and 3–10 cm broad, entire, leathery and slightly glossy, with young leaves often reddish. The flowers are large, 5–7 cm across, borne in terminal panicles 20–40 cm long, with pink to purple petals whose margins are crumpled like crêpe paper; the calyx is ribbed. The fruit is a woody, globose to ovoid capsule 2–3.5 cm long that splits into several valves to release many small winged seeds. In Vietnam it flowers profusely in late spring and summer; the chromosome number is 2n = 48.

Updated by lebachungtdh@gmail.com · 10/09/2026

According to Kew POWO, Lagerstroemia speciosa is native from South Asia (India, Sri Lanka, Bangladesh) through mainland South-East Asia (Myanmar, Thailand, Laos, Cambodia, Vietnam), southern China, Taiwan and Malesia (Malaysia, Indonesia, the Philippines) to northern Australia. It grows in open forests, along streams and on seasonally moist to dry soils in tropical and subtropical regions. For its showy flowers and shade it has been widely planted as a street and park ornamental across the tropics. In Vietnam it is commonly grown in many provinces, especially in southern cities.

Updated by lebachungtdh@gmail.com · 10/09/2026

The leaves are the most studied part; they contain corosolic acid (2α-hydroxyursolic acid), a triterpenoid regarded as the main blood-sugar-supporting active. They also contain ellagitannins such as lagerstroemin and valoneic acid dilactone, shown to inhibit glucose transport and α-amylase. Flavonoids (quercetin, kaempferol), phenolic acids (gallic acid, ellagic acid) and tannins/gallotannins contribute antioxidant and antibacterial activity. The bark and seeds also contain tannins and other triterpenes. Composition and content vary with plant part, harvest season and growing conditions.

Updated by lebachungtdh@gmail.com · 10/09/2026

Queen’s crape-myrtle is grown mainly as an ornamental and shade tree for its vivid pink-purple flowers and broad crown; its hard, strong wood is used for furniture and boat building, while the bark and leaves feature in traditional medicine. Best known is banaba tea in the Philippines, brewed from dried leaves to support blood sugar. A controlled clinical study of a standardized corosolic-acid-rich extract (Glucosol) reported a reduction in post-meal blood glucose in volunteers; pharmacological reviews report antidiabetic and anti-obesity effects of leaf extracts along with antioxidant and antibacterial activities. In folk medicine the leaves and bark are also used as a diuretic and for kidney and urinary complaints.

Updated by lebachungtdh@gmail.com · 10/09/2026

Under current assessments the species is listed as Least Concern (LC) and is not globally threatened; numerous wild populations and widespread cultivation mean it faces little pressure. As for safety, leaf preparations (banaba tea, standardized extracts) can lower blood sugar, so people taking diabetes medication should consult a doctor to avoid excessive hypoglycaemia; safety data for pregnancy and breastfeeding remain limited. Extracts should be used at the recommended dose and not as a substitute for prescribed treatment. When planted in cities, note that the roots and large crown can affect infrastructure.

Updated by lebachungtdh@gmail.com · 10/09/2026