Bioguided isolation of (9Z)-octadec-9-enoic acid from Phellodendron amurense Rupr. and identification of fatty acids as PTP1B inhibitors.

The therapy of type-2 diabetes mellitus is one of the major challenges of our age. A possible strategy to prevent the progression of this disease is the inhibition of protein tyrosine phosphatase 1B (PTP1B), a major negative regulator in the insulin and leptin signalling pathway. Phellodendri amurensis cortex is a well-known Asian herbal drug traditionally used as antiphlogistic, antibacterial, and anti-inflammatory agent, and its efficacy against diabetes-related symptoms is reported as well. However, information regarding active principle(s) or the molecular mode of action was scarce. By bioguided isolation using an IN VITRO enzyme assay with human recombinant PTP1B, (9 Z)-octadec-9-enoic acid (oleic acid) could be identified as a major PTP1B inhibitor in the bark of Phellodendron amurENSE Rupr. (Rutaceae); it showed an IC50 value of 6.2 µM. Consistent with this inhibition of PTP1B, oleic acid was capable of enhancing insulin signalling in wild-type, but not PTP1B knockout fibroblasts. By testing a series of other fatty acids of different chain length and degree of saturation, their general PTP1B-inhibitory potential in the micromolar range was observed. More pronounced effects were associated with a longer carbon backbone and saturation of the double bonds. Therefore, our work provides first scientific evidences for the antidiabetic properties of P. amurense via a new target, effects which seem to be explainable by oleic acid. The discovery of a PTP1B inhibition by many fatty acids also adds a novel facet to the pharmacological properties of a class of compounds that is found in many food items in considerable amount and triggers speculation over their possible involvement in the feedback regulation of cellular fatty acid synthesis.

Recent advances on HPLC/MS in medicinal plant analysis.

With gaining popularity of herbal remedies worldwide, the need of assuring safety and efficacy of these products increases as well. By nature they are complex matrices, comprising a multitude of compounds, which are prone to variation due to environmental factors and manufacturing conditions. Furthermore, many traditional preparations compose of multiple herbs, so that only highly selective, sensitive and versatile analytical techniques will be suitable for quality control purposes. By hyphenating high performance liquid chromatography and mass spectrometry (LC-MS) these high demands are fulfilled, providing the user with a multitude of technical options and applications. This review intends to reflect the impact of LC-MS for medicinal plant analysis focusing on most relevant reports published within the last five years. Commenced by introductory remarks to the different MS approaches most commonly used (e.g. ion trap and time of flight mass analyzers, fragmentation and ionization modes), respective LC-MS applications on the analysis of natural products in medicinal plants, commercial products and biological samples are presented. Methodological aspects like stationary and mobile phase selection or MS settings are discussed, and advantages or limitations of the described techniques are highlighted.

Bioactivity-guided isolation of 1,2,3,4,6-Penta-O-galloyl-D-glucopyranose from Paeonia lactiflora roots as a PTP1B inhibitor.

The inhibition of protein tyrosine phosphatase 1B (PTP1B) is of substantial interest for the treatment of type-2 diabetes mellitus. Using an in vitro enzyme assay with human recombinant PTP1B 1,2,3,4,6-penta-O-galloyl-D-glucopyranose was isolated from the roots of Paeonia lactiflora as an inhibitor of PTP1B, with an IC(50) value of 4.8 µM. Additionally, 1 was shown to act as an insulin sensitizer in human hepatoma cells (HCC-1.2) at a concentration of 10 µM. Thus, a potential new mechanism of action is provided explaining the antidiabetic properties of P. lactiflora.

Flow injection analysis-isotope ratio mass spectrometry for bulk carbon stable isotope analysis of alcoholic beverages.

A new method for bulk carbon isotope ratio determination of water-soluble samples is presented that is based on flow injection analysis-isotope ratio mass spectrometry (FIA-IRMS) using an LC IsoLink interface. Advantages of the method are that (i) only very small amounts of sample are required (2-5 microL of the sample for up to 200 possible injections), (ii) it avoids complex sample preparation procedures such as needed for EA-IRMS analysis (only sample dilution and injection,) and (iii) high throughput due to short analysis times is possible (approximately 15 min for five replicates). The method was first tested and evaluated as a fast screening method with industrially produced ethanol samples, and additionally the applicability was tested by the measurement of 81 alcoholic beverages, for example, whiskey, brandy, vodka, tequila, and others. The minimal sample concentration required for precise and reproducible measurements was around 50 microL L(-1) ethanol/water (1.71 mM carbon). The limit of repeatability was determined to be r=0.49%. FIA-IRMS represents a fast screening method for beverage authenticity control. Due to this, samples can be prescreened as a decisive criterion for more detailed investigations by HPLC-IRMS or multielement GC-IRMS measurements for a verification of adulteration.