Phytochemistry and pharmacology of Lagerstroemia speciosa: a natural remedy for diabetes.

Lagerstroemia speciosa (Lythraceae) has several common names, which reflect its attractive and colourful pink or purple flowers. Native to South and Southeast Asia, L. speciosa is a common ornamental tree planted along roadsides, and in gardens and parks. The species has been traditionally used in folk medicine as remedy for illnesses and ailments, particularly for lowering blood sugar level, reducing body weight, and as a remedy for diabetes. The current knowledge on the phytochemistry and pharmacology of L. speciosa is reviewed since the species has been regarded as a natural product for anti-diabetic drugs. Triterpenes, tannins, ellagic acids, glycosides and flavones have been isolated from the leaves. Pharmacological properties of the species include antioxidant, antibacterial, antiviral, anti-inflammatory, antinociceptive, anti-diarrhoeal, cytotoxic, xanthine oxidase inhibition, anti-obesity and antifibrotic activities. A more exhaustive review is accorded to its anti-diabetic properties, which have generated much research involving in vitro, animal and human studies.