Three New Hydroxytetradecenals from Amomum tsao-ko with Protein Tyrosine Phosphatase 1B and Glycogen Phosphorylase Inhibitory Activity

The fruits of Amomum tsao-ko(Cao-Guo)were documented in Chinese Pharmacopoeia for the treatment of abdominal pain,vomiting,and plague.In our previous study,a series of diarylheptanes and flavonoids withα-glucosidase and protein tyrosine phosphatase 1B(PTP1B)inhibitory activity have been reported from the middle-polarity part of A.tsao-ko,whereas the antidiabetic potency of the low-polarity constituents is still unclear.In this study,three new hydroxytetradecenals,(2E,4E,8Z,11Z)-6R-hydroxytetradeca-2,4,8,11-tetraenal(1),(2E,4E,8Z)-6R-hydroxytetradeca-2,4,8-trienal(2)and(2E,4E)-6R-hydroxytetradeca-2,4-dienal(3)were obtained from the volatile oils of A.tsao-ko.The structures of compounds 1–3 were determined using spectroscopic data involving 1D and 2D nuclear magnetic resonance(NMR),high-resolution mass spectra(HRMS),and specific rotation([α]D).Their hypoglycemic activity was evaluated against glycogen phosphorylase(GPa)and PTP1B.Compounds 1 and 2 displayed moderate activity against PTP1B with inhibition rates of 33.8%−50.3%at 100 and 200μM.Moreover,compound 1 exhibited an obvious inhibitory effect on GPa(IC50=31.7μM),whereas compound 2 was inactive.This study demonstrates hydroxytetradecenals as the characteristic components of A.tsao-ko with therapeutic potential in diabetes.