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.
Keywords: (1′S)-1′-acetoxyeugenol acetate; Alpinia galanga; Insulin; PDX-1; α-glucosidase.