Simplified HPLC method for identification of gingerol and mangiferin in herbal extracts

Quantification of bioactive compounds through modern analytical techniques is essential for proving authenticity, credibility, and safe use of herbal products in Ayurvedic medicine. In this study, we describe the development of a simplified method for the identification of key bioactive compounds in six commercial herbal products of various forms using High Performance Liquid Chromatography (HPLC). Marker compounds such as mangiferin 1 and [6]-gingerol 2 were examined in various extracts of mango leaves and ginger, respectively. The compounds were extracted by sonication with methanol at room temperature and were analyzed by HPLC with 0.1% acetic acid buffer (pH = 3.00)/methanol mixture used as gradient mobile phase. Eluents were monitored by a photo diode array (PDA) detector and UV detection fixed at 280/320 nm. Further characterization of each extract was performed using FTIR and UV-Vis. Mangiferin 1 eluted at 6 min (320 nm) and gingerol 2 at 16.9 min (280 nm). The proposed method provides a good resolution of the selected marker compounds in herbal products and dietary supplements that could be further used for their quantification and standardization in routine analysis and quality control. © EuroJournals Publishing, Inc. 2011

Diffraction effects and inelastic electron transport in angle-resolved microscopic imaging applications

We analyze the signal formation process for scanning electron microscopic imaging applications on crystalline specimens. In accordance with previous investigations, we find nontrivial effects of incident beam diffraction on the backscattered electron distribution in energy and momentum. Specifically, incident beam diffraction causes angular changes of the backscattered electron distribution which we identify as the dominant mechanism underlying pseudocolor orientation imaging using multiple, angle-resolving detectors. Consequently, diffraction effects of the incident beam and their impact on the subsequent coherent and incoherent electron transport need to be taken into account for an in-depth theoretical modeling of the energy and momentum distribution of electrons backscattered from crystalline sample regions. Our findings have implications for the level of theoretical detail that can be necessary for the interpretation of complex imaging modalities such as electron channeling contrast imaging (ECCI) of defects in crystals. If the solid angle of detection is limited to specific regions of the backscattered electron momentum distribution, the image contrast that is observed in ECCI and similar applications can be strongly affected by incident beam diffraction and topographic effects from the sample surface. As an application, we demonstrate characteristic changes in the resulting images if different properties of the backscattered electron distribution are used for the analysis of a GaN thin film sample containing dislocations

The SWELL1-LRRC8 complex regulates endothelial AKT-eNOS signaling and vascular function

The endothelium responds to numerous chemical and mechanical factors in regulating vascular tone, blood pressure, and blood flow. The endothelial volume-regulated anion channel (VRAC) has been proposed to be mechanosensitive and thereby sense fluid flow and hydrostatic pressure to regulate vascular function. Here, we show that the leucine-rich repeat-containing protein 8a, LRRC8A (SWELL1), is required for VRAC in human umbilical vein endothelial cells (HUVECs). Endothelial LRRC8A regulates AKT-endothelial nitric oxide synthase (eNOS) signaling under basal, stretch, and shear-flow stimulation, forms a GRB2-Cav1-eNOS signaling complex, and is required for endothelial cell alignment to laminar shear flow. Endothelium-restricte

Assessment on facile Diels–Alder approach of α-pyrone and terpenoquinone for the expedient synthesis of various natural scaffolds

The development of highly facile synthetic procedures for the expedient synthesis of complex natural molecules is always in demand. As this aspect, the Diels–Alder reaction (DAR) has a versatile approach to the synthesis of complex natural compounds and highly regio-/stereoselcetive heterocyclic scaffolds. Additionally, α-pyrone and terpenoquinone are two versatile key intermediates that are prevalent in various bioactive natural compounds for instance, (±)-crinine, (±)-joubertinamine, (±)-pancratistatin, (−)-cyclozonarone, and 8-ephipuupehedione, etc. Hence, the current review summarizes the Diels–Alder reaction application of α-pyrone and terpenoquinone to the constructive synthesis of various natural products over the past two decades (2001–2021). Equally, it serves as a stencil for the invention and development of new synthetic strategies for high-complex molecular structured natural and heterocyclic molecules. Graphical Abstract: [Figure not available: see fulltext.] © 2022, The Author(s).Russian Science Foundation, RSF; Council on grants of the President of the Russian Federation: 21-13-00304, HШ-2700.2020.3This work was financially supported by the Grants Council of the President of the Russian Federation (# HШ-2700.2020.3) and Russian Scientific Foundation (Grant # 21-13-00304).Council on grants of the President of the Russian Federation, HШ-2700.2020.3, Zyryanov Grigory V., Российский Фонд Фундаментальных Исследований (РФФИ), Grant # 21-13-00304, Zyryanov Grigory V

Structural and luminescence imaging and characterisation of semiconductors in the scanning electron microscope

The scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI) and hyperspectral cathodoluminescence imaging (CL) provide complementary information on the structural and luminescence properties of materials rapidly and non-destructively, with a spatial resolution of tens of nanometres. EBSD provides crystal orientation, crystal phase and strain analysis, whilst ECCI is used to determine the planar distribution of extended defects over a large area of a given sample. CL reveals the influence of crystal structure, composition and strain on intrinsic luminescence and/or reveals defect-related luminescence. Dark features are also observed in CL images where carrier recombination at defects is non-radiative. The combination of these techniques is a powerful approach to clarifying the role of crystallography and extended defects on a materials' light emission properties. Here we describe the EBSD, ECCI and CL techniques and illustrate their use for investigating the structural and light emitting properties of UV-emitting nitride semiconductor structures. We discuss our investigations of the type, density and distribution of defects in GaN, AlN and AlGaN thin films and also discuss the determination of the polarity of GaN nanowires