title: Orthosiphol A from the aerial parts of Orthosiphon aristatus is putatively responsible for hypoglycemic effect via alpha-glucosidase inhibition.
abstract: An infusion of Orthosiphon aristatus has long been used for diabetes therapy; however, the active principles remained unknown. Herein, we report the identification of the putative agents responsible for this antidiabetic activity using an a-glucosidase-guided isolation. Four flavonoids named sinensetin (1), salvigenin (2), tetramethylscutellarein (3) and 3,7,4'-tri-O-methylkaempferol (4), together with a diterpenoid named orthosiphol A (5), were characterized, based on analysis of their spectroscopic data. Flavonoids 3 and 4 inhibited yeast a-glucosidase with IC,o values of 6.34 and 0.75 mM, respectively, whereas orthosiphol A (5) selectively inhibited intestinal maltase with an IC5o, value of 6.54 mM. A kinetic investigation of 5 indicated that it retarded maltase function in a noncompetitive manner.
authors.forename: Thanakorn
authors.initials: T
authors.lastname: Damsud
authors.forename: Mary H
authors.initials: MH
authors.lastname: Grace
authors.forename: Sirichai
authors.initials: S
authors.lastname: Adisakwattana
authors.forename: Preecha
authors.initials: P
authors.lastname: Phuwapraisirisan
mesh_terms: D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D065089:Glycoside Hydrolase Inhibitors; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D031342:Orthosiphon / Q000737:chemistry*
chemical_list: D004224:Diterpenes; D065089:Glycoside Hydrolase Inhibitors; D007004:Hypoglycemic Agents; C000591727:orthosiphol A