Type 2 diabetes is a chronic multifactorial disease affecting millions of people worldwide, and new drug leads with selective α-glucosidase inhibitory activity are urgently needed [1]. In this study, the crude ethyl acetate extract of branches of Machilus litseifolia S.K.Lee showed inhibitory activity of α-glucosidase (IC50 = 8.0 ± 1.0 μg/ml), and was therefore investigated using high-resolution α-glucosidase inhibition profiling combined with high-performance liquid chromatography–high-resolution mass spectrometry–solid-phase extraction–nuclear magnetic resonance spectroscopy (HR-bioassay/HPLC-HRMS-SPE-NMR) [2]. Results from the high-resolution inhibition profile of the crude extract were used to guide preparative-scale HPLC towards five fractions correlated with bioactivity (Figure 1). Fraction 1, 4 and 5 were subjected to HR-bioassay/HPLC-HRMS-SPE-NMR using complementary analytical-scale C18 and pentafluorophenyl columns for separation as previously shown by Lima and coworkers [3]. With fraction 1, this led to trapping of 17 compounds correlated with bioactivity, of which the material eluted with peaks 7 and 8 were identified as the new compounds tamarixetin-3-O-α-L-(2'',4''-di-O-cis-coumaroyl)-rhamnopyranoside and tamarixetin-3-O-α-L-(2''-O-cis-coumaroyl-4''-O-trans-coumaroyl)-rhamnopyranoside, respectively. Structural identification of the remaining bioactive constituents from fraction 1, 4 and 5 using HPLC-HRMS-SPE-NMR is in progress.
Acknowledgements: Tuo Li acknowledges the Chinese Scholarship Council for a scholarship. Arife Önder is thanked for technical assistance.
Keywords: Machilus litseifolia, HR-bioassay/HPLC-HRMS-SPE-NMR, α-glucosidase
References:
[1] International Diabetes Federation, IDF Diabetes Atlas, 7th ed., 2015
[2] Wubshet SG, Tahtah Y, Heskes AM, Kongstad KT, Pateraki I, Hamberger B, Møller BM, Staerk D. Identification of PTP1B and α glucosidase inhibitory serrulatanes from Eremophila spp. by combined use of dual high-resolution PTP1B and α-glucosidase inhibition profiling and HPLC-HRMS-SPE-NMR. J Nat Prod 2016; 79: 1063-1072.
[3] Lima R, Gramsbergen S, Van Staden J, Jäger AK, Kongstad K, Staerk D. Advancing HPLC-PDA-HRMS-SPE-NMR analysis of coumarins in Coleonema album by use of orthogonal reversed-phase C18 and pentafluorophenyl separations. J Nat Prod 2017; 80: 1020-1027.