High-resolution α-glucosidase and radical scavenging profiling combined with HPLC-HRMS-SPE-NMR for identification of bioactive constituents in crude extract of Pueraria lobata

Pueraria lobata is a perennial leguminous vine, which is widely distributed in China where it is used as a dietary supplement and herbal medicine due to its profound pharmacological functions. P. lobata extract has previously shown antioxidant activity – one of the most important effects of functional food, dietary supplements and anticancer natural products – as well as α-glucosidase inhibitory activity – an important effect for managing blood glucose for type 2 diabetics. This work describes the identification of active constituents in P. lobata root extract by dual high-resolution α-glucosidase inhibition and radical scavenging profiling combined with HPLC-HRMS-SPE-NMR [1,2]. The resulting HR-bioassay/HPLC-HRMS-SPE-NMR analytical platform enabled pinpointing of bioactive constituents in HPLC chromatograms directly from crude extracts. Bioactive constituents were cumulatively trapped on SPE cartridges and the structures identified and elucidated by spectral data obtained in the HPLC-HRMS-SPE-NMR mode. A total of 24 compounds were identified, including the new compounds 6 and 14 (Figure 1). Several of these showed radical scavenging activity, while compunds 18 and 23 (Figure 1) showed α-glucosidase inhibitory activity.