Anti-Inflammatory and Hypoglycemic Pentacyclic Triterpenoids from the Leaves of Lagerstroemia Speciosa (L.) Pers

Giant crepe-myrtle (Lagerstroemia speciosa (L.) Pers.) has a long history of medicinal use in Southeast Asia, which is widely cultivated as a landscape plant. Its leaves are commonly brewed into tea, valued for their potential in preventing and treating diabetes and other diseases. In this study, a bioactive phytochemical investigation of the leaf led to the isolation and purification of thirty-one pentacyclic triterpenoids, including seven undescribed oleanane-type (1-3 and 6-9), five undescribed ursane-type (10-14), two undescribed lupane-type (15-16), and seventeen known pentacyclic triterpenes. Their chemical structures were elucidated based on various spectroscopic methods, including HR-ESI-MS, 1D and 2D NMR. The pentacyclic triterpenoids were evaluated for their antidiabetic and anti-inflammatory activities. Compounds 7 and 20 significantly inhibited nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 macrophages, with IC50 values of 34.12 ± 2.33 μM and 32.31 ± 4.73 μM, respectively. Additionally, compounds 1, 10, 24, 28, and 30 exhibited strong inhibitory effects on α-glucosidase. These results indicate that the leaves of L. speciosa may offer potential benefits in preventing diabetes and inflammation-related diseases.