Dual high-resolution inhibition profiling and HPLC-HRMS-SPE-NMR analysis for identification of α-glucosidase and radical scavenging inhibitors in Solanum americanum Mill

Abstract

Solanum americanum is one of the most prominent species used to treat type 2 diabetes in Guatemala. In our ongoing efforts to find antidiabetic and antioxidative compounds from natural sources, an ethyl acetate extract of this medicinal herb was investigated using dual high-resolution α-glucosidase/radical scavenging inhibition profiling. The high-resolution biochromatograms obtained by this technique were used to target subsequent structural elucidation by HPLC-HRMS-SPE-NMR analysis towards the bioactive constituents. This led to identification of 4-hydroxybenzoic acid (1) and 3-indolecarboxylic acid (6) associated with radical scavenging activity, and the amide alkaloids N-trans-p-coumaroyloctopamine (3), N-trans-p-feruloyloctopamine (4), N-trans-p-coumaroyltyramine (8) and N-trans-p-feruloyltyramine (9) correlated with α-glucosidase inhibitory activity as well as radical scavenging activity. Further analysis revealed a new lactone, methyl 5-ethyl-4-hydroxy-5-methyl-2-oxotetrahydro-2H-pyran-4-carboxylate (7) and a new steroid with a rare F ring (11). Corchorifatty acid B (12) was reported for the first time in the Solanaceae family. Their structures were elucidated by extensive use of 1D and 2D NMR spectroscopy as well as HRMS analysis.

Keywords: 3-Indolecarboxylic acid (PubChem CID: 69867); 4-Hydroxybenzoic acid (PubChem CID: 135); Antioxidants; Corchorifatty acid B (PubChem CID: 22956671); HPLC-HRMS-SPE-NMR; High-resolution bioactivity profiling; Loliolide (PubChem CID:100332); N-trans-p-Coumaroyloctopamine (PubChem CID: 23874492); N-trans-p-Coumaroyltyramine (PubChem CID: 5372945); N-trans-p-Feruloyloctopamine (PubChem CID: 24096391); N-trans-p-Feruloyltyramine (PubChem CID: 5280537); Rhamnetin 3-O-β-d-galactoside (PubChem CID: 44259577); Solanum americanum; Type 2 diabetes; p-Coumaric acid (PubChem CID: 637542); α-Glucosidase.