Inhibitory Activity of PTP1B and α-Glucosidase by Compounds from Whole Plants of Houttuynia cordata Thunb

In this study, twenty known compounds were isolated from Houttuynia cordata Thunb., including four megastigmanes (1‒4), four phenolics (5, 6, 9, and 10), one tetrahydro-2-one derivative (12), four coumarins (7, 13, 14, and 16), six caffeic acid derivatives (8, 11, 15, 17, 18, and 19), and one triterpenoid (20). Their chemical structures were established using NMR spectra and comparison with literature. The anti-diabetic activity of the isolated compounds was assessed by investigating their inhibitory effects on protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase. The results revealed that ginnalin A (10) and 3-(4′-hydroxyphenyl)-2-propenoic acid (4′′-carboxyl)-phenyl ester (13) exhibited significant inhibitory effects on both PTP1B and α-glucosidase with IC 50 values of 7.9 ‒ 37.6 and 13.9 ‒ 31.9 μM, respectively. In the kinetic study, these two compounds showed noncompetitive-type PTP1B and α-glucosidase inhibition, with K i values of 35.6 and 7.3 μM for PTP1B and 13.9 and 31.0 μM for α-glucosidase, respectively. These findings highlight the potential of the isolated compounds as candidates for the development of novel therapeutic agents for diabetes.

Anti-inflammatory and Immunosuppressive Effects of Panax notoginseng

Here, we designed to examine the anti-inflammatory effects on RAW264.7 cells and the immunosuppressive effects by evaluating interleukin-2 (IL-2) production in Jurkat T cells using a MeOH extract of Panax notoginseng roots. The results showed that the MeOH extract inhibited the synthesis of nitric oxide (NO) in a dose-dependent manner (IC₅₀ value of 7.08 µg/mL) and displayed effects on T cell activation at a concentration of 400 µg/mL. In efforts to identify the potent compounds, bioactivity-guided fractionation of the MeOH extract and chemical investigation of its active CH₂Cl₂-, EtOAc-, and butanol-soluble fractions led to the successful isolation and identification of eleven compounds, including two polyacetylenes (1, 2), a steroid saponin (3), seven dammarane-type ginsenosides (4 – 10), and an oleanane-type ginsenoside (11). Among them, compound 11 was isolated from this plant for the first time. Compound 2 exhibited potent inhibitory effects on NO synthesis and an immunosuppressive effect with IC₅₀ values of 2.28 and 65.57 µM, respectively.