α-Glucosidase inhibitors from the husks of rice Oryza sativa L.

Rice husk is one of the most plentiful agriculture by-products in rice producing areas, which harbors a substantial proportion of biological metabolites, however, it has not been well studied. As an attempt to utilize it as a productive manner, phytochemical investigation on rice husk has performed and led to the isolation of three undescribed (1, 2, and 7), along with twelve known components (3-6, and 8-15). Those chemical structures were elucidated based on massive spectroscopic methods. Among them, compounds 4, 6-8, and 10-13 have been shown to act as α-glucosidase inhibitors. Notably, the most active compounds, 10/11, demonstrated comparable α-glucosidase inhibitory effect (IC = 1.83 ± 0.11 μg/mL) to that of 1-deoxynojirimycin (IC = 1.02 ± 0.16 μg/mL). For the molecular docking simulation studies, compounds 10/11 showed relative binding interactions with α-glucosidase enzyme (PDB ID: 3A4A) that similar to those reference inhibitors. Additionally, the crude extract of O. sativa demonstrated better α-glucosidase inhibitory effect to that of isolated components, with the IC value at 1.25 ± 0.07 μg/mL.