A new TLC bioautographic assay for qualitative and quantitative estimation of lipase inhibitors.

INTRODUCTION: Lipase inhibitory assays based on TLC bioautography have made recent progress; however, an assay with greater substrate specificity and quantitative capabilities would advance the efficacy of this particular bioassay. OBJECTIVE: To address these limitations, a new TLC bioautographic assay for detecting lipase inhibitors was developed and validated in this study. METHODS: The new TLC bioautographic assay was based on reaction of lipase with ß-naphthyl myristate and the subsequent formation of the purple dye between ß-naphthol and Fast Blue B salt (FBB). The relative lipase inhibitory capacity (RLIC) was determined by a TLC densitometry with fluorescence detection, expressed as orlistat equivalents in millimoles on a per sample weight basis. Six pure compounds and three natural extracts were evaluated for their potential lipase inhibitory activities by this TLC bioautographic assay. RESULTS: The ß-naphthyl myristate as the substrate improved the detection sensitivity and specificity significantly. The limit of detection (LOD) of this assay was 0.01 ng for orlistat, the current treatment for obesity. This assay has acceptable accuracy (92.07-105.39%), intra-day and inter-day precisions [relative standard deviation (RSD), 2.64-4.40%], as well as intra-plate and inter-plate precisions (RSD, 1.8-4.9%). CONCLUSION: The developed method is rapid, simple, stable, and specific for screening and estimation of the potential lipase inhibitors.

Anti-adipogenic 18,19-seco-ursane stereoisomers and oleane-type saponins from Ilex cornuta leaves.

Three undescribed seco-ursane stereoisomers, ilexcornutosides A-C, two undescribed triterpenoid saponins, ilexcornutosides D-E, and 11 known triterpenoids were isolated from the leaves of Ilex cornuta Lindl. & Paxton. Ilexcornutosides A-C and F with the same planar structures are unique 13(18)-ene-18,19-seco-ursane skeleton triterpenoids, identified as (3S,12R)-3-O-[ß-d-glucopyranosyl-(1 â†’ 2)-α-l-arabinopyranosyl]-12-hydroxyl-19-oxo-18,19-secours-13(18)-en-28,21-lactone. Among them, ilexcornutosides A and F (or ilexcornutosides B and C) are a pair of diastereomers at the C-20 position; ilexcornutosides A and C (or ilexcornutosides B and F) are a pair of diastereomers with epimerization at the C-21. Their structures were established by extensive spectroscopic (IR, 1D and 2D NMR, and HR-ESI-MS) and chemical analyses. The absolute configurations of ilexcornutosides A, B, D and F were determined by a single crystal X-ray diffraction analysis with a Cu Kα radiation. The inhibitory effect of ilexcornutosides A-F on the PPARγ expression was assessed in the 3T3-L1-Lenti-PPARγ-Luc cells using a single luciferase reporter assay. Ilexcornutosides A and C showed a comparable activity in decrease of the PPARγ expression to the positive control (T0070907) at 5 µM.

Direct coupling of thin-layer chromatography-bioautography with electrostatic field induced spray ionization-mass spectrometry for separation and identification of lipase inhibitors in lotus leaves.

In situ profiling compounds in complex matrices is important technology to develop in analytic chemistry. The aim of this study is to develop a direct coupling method of thin layer chromatography (TLC) to mass spectrometry (MS) via electrostatic field induced spray ionization (EFISI). We proposed a surface treatment method of normal-phase thin layer chromatography (TLC) plates with dimethyl silicone oil coating which successfully allowed TLC to couple to MS via EFISI. Different parameters affecting the ionization efficiency were investigated and optimized, including silicone oil concentrations, air-drying times, applied voltages, and TLC plate types. This optimized TLC-EFISI-MS method was successfully applied to examine lipase inhibitory components present in lotus leaves. Six active alkaloids including three aporphines and three benzylisoquinolines were profiled with their MSn (n = 4) data, or with a comparison with reference substances. This is the first report on the coupling EFISI-MS to TLC or TLC bioautography for in situ identification of active natural products.