Four new phenolic compounds from the fruits of Alpinia galanga

Eleven phenolic compounds including four new ones, (R)-4-(1-methoxypropyl)phenol (1), (S)-3-(4-hydroxy-3-methoxyphenyl)propane-1,2-diyldiacetate (2), (R)-3-(4-hydroxy-3-methoxyphenyl)propane-1,2-diyldiacetate (3) and 3′-demethoxycrataegusanoid E (4), were isolated from the fruits of Alpinia galanga. The structures of new compounds were elucidated on the basis of extensive spectroscopic data (1D and 2D NMR, [α]D, HRESIMS, UV and IR). All the isolates were assayed for their antidiabetic potency against PTP1B and α-glycosidase enzymes, and glucagon-like peptide-1 (GLP-1) promotion. Compound 4 showed significant inhibition on PTP1B with an IC50 value of 58.4 μM, and compound 6 showed α-glycosidase inhibitory activity with an IC50 value of 97.6 μM. Compounds 1–4 and 7–11 could stimulate GLP-1 secretion in NCl-H716 cells with promoting rates of 770.5–1943.1 % (50 μM). This study provides information for understanding the antidiabetic constituents of A. galanga.