Engineered Glycosidase for Significantly Improved Production of Naturally Rare Vina-Ginsenoside R7.

Ginsenosides are the main bioactive ingredients in plants of the genus Panax. Vina-ginsenoside R7 (VG-R7) is one of the rare high-value ginsenosides with health benefits. The only reported method for preparing VG-R7 involves inefficient and low-yield isolation from highly valuable natural resources. Notoginsenoside Fc (NG-Fc) isolated in the leaves and stems of Panax notoginseng is a suitable substrate for the preparation of VG-R7 via specific hydrolysis of the outside xylose at the C-20 position. Here, we first screened putative enzymes belonging to the glycoside hydrolase (GH) families 1, 3, and 43 and found that KfGH01 can specifically hydrolyze the ß-d-xylopyranosyl-(1 → 6)-ß-d-glucopyranoside linkage of NG-Fc to form VG-R7. The I248F/Y410R variant of KfGH01 obtained by protein engineering displayed a kcat/KM value (305.3 min-1 mM-1) for the reaction enhanced by approximately 270-fold compared with wild-type KfGH01. A change in the shape of the substrate binding pockets in the mutant allows the substrate to sit closer to the catalytic residues which may explain the enhanced catalytic efficiency of the engineered enzyme. This study identifies the first glycosidase for bioconversion of a ginsenoside with more than four sugar units, and it will inspire efforts to investigate other promising enzymes to obtain valuable natural products.

Unusual Prenylated Stilbene Derivatives with PTP1B Inhibitory Activity from Artocarpus styracifolius.

In an effort to identify agents from natural products that inhibit protein tyrosine phosphatase 1B (PTP1B), 5 new prenylated stilbenes, (±)-styrastilbene A (1: ), styrastilbene B (2: ), and (±)-styrastilbenes C - E (3, 4: , and 7: ), along with 4 known structurally related compounds (5, 6, 8: , and 9: ), were isolated from the roots of Artocarpus styracifolius. Their structures were elucidated by spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectrometry (HRESIMS), ultraviolet (UV), and infrared (IR). Based on these isolates, a new plausible biosynthetic pathway for the unusual stilbene derivatives 3: -8: with a tetracyclic ring system is proposed. Among these compounds, 1: -3, 8: , and 9: displayed significant PTP1B inhibitory effects with IC50 values ranging from 2.40 (95% confidence interval [CI]: 2.21 - 2.59) to 8.80 (95% CI: 8.28 - 9.32) µM. Moreover, kinetic analysis and molecular docking simulations were performed to provide insight into the inhibition type as well as the interaction and binding mode of these active isolates with PTP1B. Our results revealed mixed-type PTP1B inhibition for all compounds tested. Docking simulations of these stilbene derivatives showed negative binding energies and close proximity to residues at the allosteric and catalytic sites of PTP1B. These findings suggest that these compounds may have a potential to be further developed as agents for the management of type 2 diabetes mellitus.