High-resolution assays combined with HPLC-HRMS-SPE-NMR for identification of antidiabetic constituents in Vietnamese plants

Type-2 diabetes is affecting 246 million. Patients with type-2 diabetes suffer from complications as high blood pressure, blindness, kidney failure, lower limb amputation, heart disease and stroke.

20 Medicinal plants traditionally used in Vietnam for the management of diabetes were collected and investigated for inhibition of carbohydrate-hydrolysing enzymes.

Chloroform, ethanol and water extracts of 20 plants were evaluated for α-glucosidase and α-amylase inhibitory activity. Analytical-scale HPLC was then used to investigate the most active extracts, where samples without tannins were identified and fractionated into 96-well microplates, followed by α-glucosidase [1] and α-amylase [2] inhibition assays.

Ethanol and water extracts of Phyllanthus amarus, Phyllanthus urinaria, Lagerstroemia speciosa, Nepenthes mirabilis, Syzygium cumini, Rhizophora mucronata and Kandelia candel had IC₅₀ below 40 µg/mL in the α-glucosidase assay. Ethanol extracts of Kandelia candel and Ficus racemosa inhibited α-amylase (IC₅₀ 7.66 and 46.70 µg/mL, respectively).

Having no tannin constituents, P. amarus, P. urinaria, L. speciosa water extracts and F. racemosa ethanol extract were chosen for fractionation followed by α-glucosidase and α-amylase inhibition assays. Biochromatograms of P. amarus and P. urinaria water extracts showed several active compounds against α-glucosidase.

Biochromtogram of P. amarus and P. urinaria water extracts have many promising peaks with more than 90% inhibitory activity. The biochromatograms constructed from these assays allowed fast identification of active compounds responsible for antidiabetic activity. Subsequent HPLC-HRMS-SPE-NMR experiments will allow the isolation and structural elucidation.

References:

[1] Schmidt JS et al. Food Chem 2012; 135: 1692 – 1699 [2] Okutan L et al. J Agric Food Chem 2014; 62: 11465 – 11471