Diterpenoid and phenolic constituents from corn silk (Zea mays) with PTP1B inhibitory activity

Abstract

Chemical investigation of corn silk resulted in the isolation of nine secondary metabolites, including a new ent -kaurane diterpenoid, zeamaysditerpene A ( 1 ) and eight known compounds, stigmaydene A ( 2 ), stigmaydene J ( 3 ), stigmaydene L ( 4 ), stigmane D ( 5 ), demethyltorosaflavone D ( 6 ), chrysoeriol 6- C - β -boivinopyranosyl-7- O - β -D-glucopyranoside ( 7 ), deoxypodophyllotoxin ( 8 ), and α -peltatin glucoside ( 9 ). Their structures were elucidated using a combination of spectroscopic methods, including 1D and 2D NMR and HRESIQTOF mass spectra. The absolute configuration of 1 was deduced by applying electronic circular dichroism (ECD) calculation method. Among the isolates, only 6 displayed significant inhibition against PTP1B activity in a dose-dependent manner, with an IC 50 value of 10.7 ± 0.1 µM. Furthermore, molecular docking simulation was carried out to explore the action perspective of 6 inside the enzyme PTP1B. This finding suggests that 6 might be a potential lead for the development of a new anti-diabetic agent.