Pentacyclic Triterpenoids from Astilbe rivularis that Enhance Glucose Uptake via the Activation of Akt and Erk1/2 in C2C12 Myotubes

Glucose uptake into insulin-sensitive tissues is important for the regulation of blood glucose. This study has investigated whether the pentacyclic triterpenoids substituted with a carboxylic acid at the C-27 position isolated from Astilbe rivularis can enhance glucose uptake and subsequently to also examine their underlying molecular mechanisms. The structure of the new pentacyclic triterpenoid <b>1</b> was assigned by spectroscopic data interpretation. To evaluate the activity of compounds <b>1</b> and <b>2</b>, glucose uptake and glucose transporter 4 (GLUT4) translocation were measured in C2C12 myotubes. The C-27-carboxylated triterpenoids <b>1</b> and <b>2</b> significantly increased basal and insulin-stimulated glucose uptake and GLUT4 translocation to plasma membrane. Both compounds stimulated the phosphorylation of insulin receptor substrate-1 (IRS-1), protein kinase B (Akt), and extracellular signal-regulated kinase 1/2 (Erk1/2). Pretreatment with the Akt inhibitor triciribine or the Erk1/2 inhibitor U0126 decreased the ability of both compounds to enhance basal- and insulin-stimulated glucose uptake and stimulate GLUT4 translocation. These results indicate that compounds <b>1</b> and <b>2</b> activated both the IRS-1/Akt and Erk1/2 pathways and subsequently stimulated GLUT4 translocation, leading to enhanced glucose uptake. Thus, these observations suggest that C-27-carboxylated-pentacyclic triterpenoids may serve as scaffolds for development as agents for the management of blood glucose levels in disease states such as diabetes

A new naphthoquinone analogue and antiviral constituents from the root of <i>Rhinacanthus nasutus</i>

<p><i>Rhinacanthus nasutus</i> (L.) Kurz (Acanthaceae) is known as traditional medicine for the treatment of fungal and herpes virus infections. A new naphthoquinone racemate, rhinacasutone (<b>1</b>) together with seven known compounds, rhinacanthone (<b>2</b>), rhinacanthins C, D, N, Q, and E (<b>3</b>–<b>7</b>), and heliobuphthalmin (<b>8</b>) were isolated from root of <i>R. nasutus.</i> Their structures were determined on the basis of extensive spectroscopic methods, including 1D-, 2D-NMR and MS data. All the isolated compounds were tested for their antiviral activities against PR8, HRV1B, and CVB3-infected vero cells. Compounds <b>3</b>–<b>6</b> exhibited significant antiviral activities with the IC₅₀ value ranging from 0.03 to 23.7 μM in all three infections.</p