Quadruple high-resolution α-glucosidase/α-amylase/PTP1B/radical scavenging 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 root bark of Morus alba L.

In this paper, quadruple high-resolution alpha-glucosidase/alpha-amylase/PTP1B/radical scavenging profiling combined with HPLC-HRMS-SPE-NMR were used for studying the polypharmacological properties of crude root bark extract of Morus alba L. This species is used as an anti-diabetic principle in many traditional treatment systems around the world, and the crude ethyl acetate extract of M. alba root bark was found to inhibit alpha-glucosidase, alpha-amylase and protein-tyrosine phosphatase 1B (PTP1B) with IC50 values of 1.70 +/- 0.72, 5.16 +/- 10.69, and 5.07 +/- 0.68 mu g/mL as well as showing radical scavenging activity equaling a TEAC value of (3.82 +/- 0.14) x 10(4) mM per gram extract. Subsequent investigation of the crude extract using quadruple high-resolution alpha-glucosidase/alpha-amylase/PTP1B/radical scavenging profiling provided a quadruple biochromatogram that allowed direct correlation of the HPLC peaks with one or more of the tested bioactivities. This was used to target subsequent HPLC-HRMS-SPE-NMR analysis towards peaks representing bioactive analytes, and led to identification of a new Diels-Alder adduct named Moracenin E as well as a series of Diels-Alder adducts and isoprenylated flavonoids as potent alpha-glucosidase and alpha-amylase inhibitors with IC50 values in the range of 0.60-27.15 mu M and 1.22-69.38 mu M, respectively. In addition, these compounds and two 2-arylbenzofurans were found to be potent PTP1B inhibitors with IC50 values ranging from 4.04 to 21.67 mu M. The high-resolution radical scavenging profile also revealed that almost all of the compounds possess radical scavenging activity. In conclusion the quadruple high resolution profiling method presented here allowed a detailed profiling of individual constituents in crude root bark extract of M. alba, and the method provides a general tool for detailed mapping of bioactive constituents in polypharmacological herbal remedies. (C) 2018 Elsevier B.V. All rights reserved.