α-Glucosidase inhibitory, antibacterial, and antioxidant activities of natural substances from the wood of Derris reticulata Craib.

Derris reticulata (Leguminosae-Papilionoideae) has been used for the treatment of diabetes in Thai folk remedies. The phytochemical investigation of the wood of D. reticulata revealed the isolation of two new pyranoflavanones, 4'-methoxydereticulatin (1) and 2'''-hydroxy,3'''-ethoxylupinifolin (2), along with five known compounds namely lupinifolin (3), 2''',3'''-dihydroxylupinifolin (4), genistein (5), lupeol (6), and β-sitosterol (7). Compounds 1-4 were selected for antibacterial assay using broth microdilution method, and displayed good activity against four out of five tested pathogenic bacterial strains, with MIC values ranging from 0.78 to 128 μg/mL. The result from spectrophotometric assay of α-glucosidase inhibition showed that 5 exhibited promising α-glucosidase inhibitory activity, compared with the positive control acarbose. Additionally, it was found that compounds 4 and 5 showed moderate DPPH and NO radicals scavenging activity. Modeling studies were also performed to suggest the interaction modes of compounds 3-5 in the α-glucosidase enzyme active site.