(1' S )-1'-Acetoxyeugenol Acetate Enhances Glucose-Stimulated Insulin Secretion.

Alpinia galanga have been widely used as spice or traditional medicine in East Asia, commonly known as Thai ginger. In the present study, seven major phenylpropanoids, (±)-1'-hydoxychavicol acetate ( 1 ; HCA), (1' S )-1'-acetoxychavicol acetate ( 2 ; ACA), (1' S )-1'-acetoxyeugenol acetate ( 3 ; AEA), eugenyl acetate ( 4 ), trans - p -coumaraldehyde ( 5 ), trans - p -acetoxycinnamyl alcohol ( 6 ), and trans - p -coumaryl diacetate ( 7 ), were isolated from the 95% EtOH and hot water extracts of the rhizomes of A . galanga by chromatographic method. Phenylpropanoids 1 - 7 were evaluated for glucose-stimulated insulin secretion (GSIS) effect and α-glucosidase inhibitory activity. Phenylpropanoids 1 - 4 increase GSIS effect without cytotoxicity in rat INS-1 pancreatic β-cells. In addition, INS-1 cells were treated with AEA ( 3 ) to determine a plausible mechanism of β-cell function and insulin secretion through determining the activation of insulin receptor substrate-2 (IRS-2), phosphatidylinositol 3-kinase (PI3K), Akt, and pancreatic and duodenal homeobox-1 (PDX-1). Upon treatment with AEA ( 3 ), INS-1 cells showed an increase in these protein expressions. Meanwhile, AEA ( 3 ) exhibited α-glucosidase inhibitory activity. On the basis of the above findings, we suggest AEA ( 3 ) as a potential antidiabetic agent.