Prenylated Flavanone Enantiomers with α-Glucosidase Inhibitory Activity from the Root Bark of Morus alba.

A focused chemical investigation into the polar fractions of a well-known traditional Chinese medicine called Sang-Bai-Pi (the root bark of Morus alba) yielded a panel of prenylated flavanones. The new compounds were identified as four pairs of enantiomers (1a/1b-4a/4b) featuring the same constitution structure, on the basis of HRMS, NMR and ECD analyses. Several previously reported known racemic co-metabolites were also analyzed and separated by HPLC on chiral columns, and the absolute configurations of pure enantiomers were established via ECD technique for the first time. The inhibition of these isolates against the antidiabetic target α-glycosidase was further tested, with most of them showing decent inhibitory activity compared with the positive control acarbose. The interaction mechanism of two selected compounds (3a & 4b) was explored by kinetics experiment, which revealed a mixed type of inhibition pattern toward the enzyme.

High-performance thin-layer chromatography/bioautography and liquid chromatography-mass spectrometry hyphenated with chemometrics for the quality assessment of Morus alba samples.

Quality control is a crucial step in the production of effective and safe herbal remedies. The aim of this study was to develop a new, simple, and high throughput procedure for the quality assessment of herbal drugs using a high-performance thin-layer chromatography (HPTLC)/bioautography and UPLC-MS/MS approach combined with chemometrics. This was exemplarily shown for Morus alba L. root bark (sang bái pí; SBP). Bioautography assays were developed for the identification of constituents with radical scavenging (DPPH assay) and antimicrobial activities (Bacillus subtilis, Escherichia coli) of 18 different M. alba samples, which was supported by UPLC-MS/MS analysis. Further, the combination of bioautography and chemometrics identified those samples with the most bioactive constituents. Plant materials collected from Serbia (11 samples) showed higher both radical scavenging and antimicrobial activities compared to samples provided from China (7 samples). Principal component analysis (PCA) confirmed the discrimination of geographically different samples and recognized their main markers responsible for differences between Serbian and Chinese samples. Most importantly for quality assessment, the combined HPTLC/bioautography and UPLC-MS/MS approach not only allowed for a fast chemical profiling of the investigated samples and their unambiguous identification, but also for the disclosure of major and minor bioactive constituents present in SBP.