Effect of ginsenosides on glucose uptake in human Caco-2 cells is mediated through altered Na+/glucose cotransporter 1 expression.

In this study, we measured the effect of ginsenosides on glucose uptake using the Caco-2 cell system. At submicromolar concentrations, these compounds exhibited marked effects on the rate of glucose transport across the differentiated Caco-2 cell monolayer. Compound K (CK), the main intestinal bacterial metabolite of the protopanaxadiol ginsenosides, significantly enhanced the steady-state glucose transport rate to about 50% of the control sample rate (from 1.54 +/- 0.09 to 2.25 +/- 0.15 nmol/min). Conversely, the protopanaxatriol ginsenoside Rg1 inhibited glucose transport to about 70% of the original rate (from 1.54 +/- 0.09 to 1.02 +/- 0.05 nmol/min). Consistent with the effect on glucose uptake rate, CK and Rg1 conferred a significant and paralleled alteration on both the protein and mRNA expression levels of the Na+/glucose cotransporter 1 (SGLT1) gene. Unlike SGLT1, there is no significant alteration on the protein or mRNA levels of GLUTs in CK- or Rg1-treated cells. Taken together, our results demonstrate that ginsenosides CK and Rg1 elicited potent enhancing and suppressing effects, respectively, on glucose uptake across human intestinal Caco-2 monolayer through modulation of SGLT1 expression.

Cytotoxic effect of triterpenoids from the root bark of Hibiscus syriacus.

In this study, 4 new triterpenoids-3ß- acetoxy-olean-11-en,28,13ß-olide (1), 3ß- acetoxy-11α,12α-epoxy-olean-28,13ß-olide (2), 19α-epi-betulin (3), and 20, 28-epoxy-17ß,19ß-lupan-3ß-ol (4)-and 12 known compounds, were isolated from the root bark of Hibiscus syriacus L. by using acetone extraction. Their structures were characterized by extensive spectroscopic analysis. To investigate cytotoxicity, A549 human lung cancer cells were exposed to the extract and the compounds identified from it. Significantly reduced cell viability was observed with betulin-3-caffeate (12) (IC50, 4.3 µM). The results of this study indicate that betulin-3-caffeate (12) identified from H. syriacus L. may warrant further investigation for potential as anticancer therapies.

Alkaloids from Coptis chinensis root promote glucose uptake in C2C12 myotubes.

The root of Coptis chinensis Franch. (COCH) is regularly used for medicinal purposes, and has been prescribed alone or in combination with other traditional herbs for the treatment of diabetes. To investigate the effects of COCH on glucose utilization by skeletal muscles, we prepared an ethanol extract of COCH root (COCH-Et) partitioned with dichloromethane, n-butanol, and water and tested its effects on glucose uptake in differentiated C2C12 myotubes. We found that dichloromethane and n-butanol sub-fractions of COCH-Et promoted glucose uptake in differentiated C2C12 cells at 50 µg/mL. Further fractionation of these preparations by using column chromatography, analysis of their effects on glucose uptake and characterization using nuclear magnetic resonance, mass spectrometry, and thin layer chromatography helped identify two new alkaloids, 8,13-dioxocoptisine hydroxide (1) and coptisonine (2), together with eleven known compounds. These were isolated from the dichloromethane layer of COCH-Et. In particular, exposure of C2C12 cells to berberine (6) at 12.5 and 6.25 µg/mL for 24h resulted in significant promotion of glucose uptake. Coptisonine (2) and octadecyl caffeate (9) also stimulated glucose uptake at 25 and 50 µg/mL. These findings indicate that active constituents of COCH root may help alleviate hyperglycemia in diabetes by promoting glucose uptake by skeletal muscles.