High-resolution α-glucosidase inhibition profiling combined with HPLC-HRMS-SPE-NMR for identification of anti-diabetic compounds in Eremanthus crotonoides (Asteraceae)

Type 2 Diabetes (T2D) is a chronic metabolic disorder, that is expected to affect more than 500 million people worldwide in 2030 [1]. α-Glucosidase slows down the cleavage and absorption of monosaccharides from complex dietary carbohydrates, and represents therefore an important class of drugs for management of T2D [2]. In this study, crude ethanol extract of Eremanthus crotonoides leaves was investigated by high-resolution α-glucosidase inhibition profiling combined with HPLC-HRMS-SPE-NMR [3,4]. The HPLC chromatogram (in blue) and the α-glucosidase inhibition profile (in red) is shown in the figure below – and this shows a series of HPLC peaks in the retention time range 40 – 65 min associated with α-glucosidase inhibitory activity. The region from 40 – 48 min were reseparated using a pentafluorophenyl HPLC column for a complementary separation method compared to C₁₈ This led to identification of six α-glucosidase inhibitors, i.e., quercetin (16), trans-tiliroside (17), luteolin (19), quercetin-3-methyl ether (20), 3,4-dicaffeoylquinic acid n-butyl ester (26), and 3,5-dicaffeoylquinic acid n-butyl ester (29).

The bioactive compounds were subsequently isolated by preparative-scale HPLC for IC₅₀ determination, and the most active compounds were the two isobaric dicaffeoylquinic acid derivatives 26 and 29 with IC₅₀ values of 3.7 and 5.1µM, respectively. This is the first report of the α-glucosidase inhibitory activity of compounds 26 and 29, and support the important role of Eremanthus species as sources of new drug leads and/or herbal remedies for management of T2D.

Acknowledgements: CAPES for the financial support.

Keywords: Diabetes, HPLC-HRMS-SPE-NMR, α-glucosidase, Eremanthus crotonoides.

References:

[1] Whiting DR, Guariguata L, Weil C, Shaw J. IDF diabetes atlas: global estimates of the prevalence of diabetes for 2011 and 2030. Diabetes Res Clin Pract 2011; 94: 311 – 321

[2] Lebovitz HE. Alpha-glucosidase inhibitors. Endocrinol Metabol Clin North Am 1997; 26: 539 – 551

[3] Kongstad KT, Özdemir C, Barzak A, Wubshet SG, Staerk D. Combined use of high-resolution α-glucosidase inhibition profiling and HPLC-HRMS-SPE-NMR for investigation of antidiabetic principles in crude plant extracts. J Agric Food Chem 2015; 63: 2257 – 2263

[4] Tahtah Y, Kongstad KT, Wubshet SG, Nyberg NT, Jønsson LH, Jäger AK, Qinglei S, Staerk D. Triple aldose reductase/α-glucosidase/radical scavenging high-resolution profiling combined with high-performance liquid chromatography – high-resolution mass spectrometry – solid-phase extraction – nuclear magnetic resonance spectroscopy for identification of antidiabetic constituents in crude extract of Radix Scutellariae. J Chromatogr A 2015; 1408: 125 – 132