Antidiabetic constituents of Dendrobium officinale as determined by high-resolution profiling of radical scavenging and α-glucosidase and α-amylase inhibition combined with HPLC-PDA-HRMS-SPE-NMR analysis

Type 2 diabetes is a chronic metabolic disorder affecting millions of people worldwide, and new drug leads are urgently needed. The dried stem of Dendrobium officinale is used in China to alleviate the symptoms of diabetes, but investigations of its bioactive components have been limited. We have applied a simple, fast, and effective method, combining triple high-resolution profiling of radical scavenging and alpha-glucosidase and alpha-amylase inhibition with high-performance liquid chromatography - photodiode-array detection - high-resolution mass spectrometry - solid-phase extraction - nuclear magnetic resonance spectroscopy (HR-bioassay/HPLC-PDA-HRMS-SPE-NMR). Two new compounds, 3,4,4'-trihydroxy-5-methoxybibenzyl (5) and 3,4-dihydroxy-3',4',5-trimethoxybibenzyl (8a), along with fourteen known compounds, were identified. Twelve of these were associated with radical scavenging activity, six with alpha-glucosidase inhibition, and one with a-amylase inhibition. Compound 5, dendrocandin U, and 3,4-dihydroxy-4',5-dimethoxybibenzyl (12) are reported as alpha-glucosidase inhibitors for the first time, and 12 is furthermore reported as an alpha-amylase inhibitor for the first time.