Background/Aims: Previously we described insulinotropic effects of Leonurus sibiricus L. plant extracts used for diabetes mellitus treatment in Traditional Mongolian Medicine. The flavonoid quercetin and its glycoside rutin, which exert anti-diabetic properties in vivo by interfering with insulin signaling in peripheral target tissues, are constituents of these extracts. This study was performed to better understand short- and long-term effects of quercetin and rutin on beta-cells. Methods: Cell viability, apoptosis, phospho-protein abundance and insulin release were determined using resazurin, annexin-V binding assays, Western blot and ELISA, respectively. Membrane potentials (V_mem), whole-cell Ca²⁺ (ICa)- and ATP-sensitive K⁺ (IK_ATP) currents were measured by patch clamp. Intracellular Ca²⁺ (Ca_i) levels were measured by time-lapse imaging using the ratiometric Ca²⁺ indicator Fura-2. Results: Rutin, quercetin and the phosphoinositide-3-kinase (PI3K) inhibitor LY294002 caused a dose-dependent reduction in cell viability with IC₅₀ values of ∼75 µM, ∼25 µM and ∼3.5 µM, respectively. Quercetin (50 µM) significantly increased the percentage of Annexin-V+ cells within 48 hrs. The mean cell volume (MCV) of quercetin-treated cells was significantly lower. Within 2 hrs, quercetin significantly decreased basal- and insulin-stimulated Akt(T308) phosphorylation and increased Erk1/2 phosphorylation, without affecting P-Akt(S473) abundance. Basal- and glucose-stimulated insulin release were significantly stimulated by quercetin. Quercetin significantly depolarized V_mem by ∼25 mV which was prevented by the K_ATP-channel opener diazoxide, but not by the L-type ICa inhibitor nifedipine. Quercetin significantly stimulated ICa and caused a 50% inhibition of IK_ATP. The effects on V_mem, ICa and IK_ATP rapidly reached peak values and then gradually diminished to control values within ∼1 minute. With a similar time-response quercetin induced an elevation in Ca_i which was completely abolished in the absence of Ca²⁺ in the bath solution. Rutin (50 µM) did not significantly alter the percentage of Annexin-V+ cells, MCV, Akt or Erk1/2 phosphorylation, insulin secretion, or the electrophysiological behavior of INS-1 cells. Conclusion: We conclude that quercetin acutely stimulates insulin release, presumably by transient K_ATP channel inhibition and ICa stimulation. Long term application of quercetin inhibits cell proliferation and induces apoptosis, most likely by inhibition of PI3K/Akt signaling.

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Interest in botanical medicines is increasing worldwide with current global market values estimated to be greater than US $72 billion. To ensure ingredients used in botanical preparations are appropriately identified and will deliver the intended benefit while minimizing potential for risk, good manufacturing practices (GMPs) are required. GMPs require that scientifically valid analytical techniques be used. This review discusses a variety of techniques of quality assessment taking into account the different challenges between academicians and manufacturers with the basic premise that all techniques are scientifically valid if used appropriately, and conversely, are limited if not used in a scientifically valid manner. The strengths and limitations, applications and inapplicability, of some of these techniques will be discussed, as will differences between traditional and more modern analytical techniques. A strong emphasis is placed on classical botanical and traditional macromorphological assessment techniques that represent the basis of identification and quality assessment upstream of other techniques such as analytical chemistry and genetics. It will be shown that it is the suite of botanical and chemical techniques that provides the greatest confidence for ensuring the identity and quality of botanical medicines.

This is the first detailed report of secondary metabolites of C. calolepis. Evaluation of biological activity of cnicin establishes the potential of this compound as an anti-inflammatory and cytotoxic agent.

The investigation of a dichloromethane extract of flower heads of a Hungarian taxon of the Achillea millefolium group led to the isolation of three flavonoid aglycones, one triterpene, one germacranolide and five guaianolides. Their structures were elucidated by UV-VIS, EI- and CI-MS, 1H NMR and 13C NMR spectroscopic methods as well as by 2D-NMR studies and by selective 1D-NOE experiments. Besides apigenin, luteolin and centaureidin, β-sitosterol, 3β-hydroxy-11α,13-dihydro-costunolide, desacetylmatricarin, leucodin, achillin, 8α-angeloxy-leucodin and 8α-angeloxy-achillin were isolated. Both latter substances are reported here for the first time. Their NMR data were compared with those of the other guaianolides. The stereochemistry of 3β-hydroxy-11α,13-dihydro-costunolide was discussed and compared with data of the literature.