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Two new thiophene derivatives (1 and 2), a new sesquiterpene (3), and 15 known compounds (4–18) were isolated from the whole plants of Artemisia rupestris. The new compounds (1–3) were elucidated by extensive spectroscopic techniques including 1 D (1H and 13C) and 2 D NMR experiments (COSY, HSQC, HMBC and NOESY), and HR-ESI-MS. Most of the isolates (1–6, 8, 10–18) exhibited the neuraminidase inhibitory activity with IC50 values ranging from 74.07–986.54 μM by a fluorescence-based assay. Two known flavonoids (chrysosplenetin B and luteolin) showed a comparable activity to oseltamivir acid on neuraminidase inhibition. [ABSTRACT FROM AUTHOR]

Introduction: Dragendorff's reagent has low sensitivity and non‐specificity for some alkaloids. A new alkaloid derivatisation reagent has been developed and optimised by using a Box–Behnken design method. This new reagent is applicable for structurally diverse natural alkaloids, and is proposed as a universal alkaloid staining reagent. Objective: To establish an efficient and sensitive thin‐layer chromatography (TLC) identification method for Leonuri Herba and Leonuri Fructus to characterise their differences and similarities. Method: Three key components (bismuth subnitrate, potassium iodide and iodine) in the derivatisation reaction were re‐constructed and optimised using a response surface method. Different inorganic acids, essential additives of the staining reaction, were compared by a single‐factor experiment design. Results: This newly optimised reagent for alkaloids reported in this study, named the enhanced Dragendorff–Wagner's reagent, is composed of 0.82% bismuth subnitrate, 11.1% potassium iodide and 0.76% iodine in 38% phosphoric acid solution. Validation results indicate that the TLC spot of stachydrine stained with the enhanced Dragendorff–Wagner's reagent had a limit of detection of 2.0 μg, good intra‐ and inter‐plate, and intra‐ and intra‐day precisions with relative standard devition values less than 5.0%, and stability over 90 min. Conclusion: This enhanced Dragendorff–Wagner's reagent was applied for TLC identification of 16 reference alkaloids representing 11 structural skeletons, and two closely related herbs (Leonuri Herba and Leonuri Fructus). This newly enhanced Dragendorff–Wagner's reagent is a universal, effective, and sensitive staining reagent for alkaloids. A new derivatization reagent for TLC analysis of alkaloids, named enhanced Dragendorff‐Wagner's reagent, was re‐constructed and optimized. This enhanced Dragendorff‐Wagner's reagent was successfully applied for TLC identification of two closely related herbs (Leonuri Herba and Leonuri Fructus). This universal derivatization reagent was found to positive detection for 16 reference alkaloids representing 11 structural skeletons. [ABSTRACT FROM AUTHOR]

Introduction: Glucosinolates (1–5) are important secondary metabolites found in Isatis indigotica roots. Due to their high hydrophilic and ionic nature, purified glucosinolates often contain salt impurities and moisture. Accurate assessment of their purities is important for glucosinolates being utilised as chemical markers. Objective: To develop and validate quantitative proton (1H) nuclear magnetic resonance (qHNMR) methods for purity assessments of aliphatic and indole glucosinolates (1–5). Method: Several NMR parameters such as pulse program, relaxation time, and delay time were optimised. Three qHNMR methods were developed using gluconapin (3), neoglucobrassicin (4), and sinigrin (5) for method validation and with maleic acid as internal standard. Results: The quantification was based on the integrated area ratios of an olefinic proton (H‐4 for 1–3; H‐6 for 4; and H‐3 for 5) of the side chain from glucosinolates relative to the olefinic proton from the internal standard using deuterated water (D2O) as the solvent. The qHNMR methods were successfully applied for purity assessments of four aliphatic glucosinolates (1–3 and 5: progoitrin, epiprogoitrin, gluconapin, and sinigrin), and an indole glucosinolate (4: neoglucobrassicin). Conclusion: The purity of glucosinolates isolated from I. indigotica and commercial sinigrin was accurately assessed using the developed qHNMR method. The qHNMR provides a reliable and superior means to determine the purity of glucosinolates. Three qHNMR methods were developed and validated for purity assessment of aliphatic and indole glucosinolates using maleic acid as internal standard. The quantification was based on integrated area ratios of an olefinic proton of the side chain from glucosinolates relative to the olefinic proton from internal standard. The qHNMR method is a simple, rapid, irreplaceable, and accurate approach for purity assessments of glucosinolates. [ABSTRACT FROM AUTHOR]

A Class D amplifier comprises a pulse width modulator and an output stage. In this paper, we analyze the power dissipation mechanisms and derive the overall power efficiency of the output stage realized using the finger and waffle layouts. We compare the relative merits of these layouts. We propose two design methodologies to determine the aspect ratios of the transistors in the output stage for optimum power efficiency (optimum for a given fabrication process, supply voltage and load resistance): 1) optimization to a single modulation index point and 2) optimization to a range of modulation indexes. For the design of an output stage with optimum power efficiency (and small IC area), we recommend optimization to a range of modulation indexes and a layout realized by the waffle structure. The theoretical analysis and derivations are verified on the basis of computer simulations and measurements on fabricated prototype IC's. Index Terms--Amplifier, Class D, efficiency, optimization, output stage.

A new triterpenoid glycoside (1) and 15 known compounds (2-16) were isolated from the whole plants of Gueldenstaedtia verna. The new compound (1) was identified as complogenin 22-O-β-d-glucopyranoside by extensive spectroscopic techniques including 1D (1H and 13C) and 2D NMR experiments (HSQC, HMBC and NOESY), HR-DART-MS and chemical methods. Most of the isolates were evaluated for their inhibitory activities on LPS-induced NO production in RAW 264.7 cells. The inhibitory effects of the active compounds, sulphuretin (8) and (22E,24S)-5α,8α-epidioxy-24-methyl-cholesta-6,9(11),22-trien-3β-ol (13), on the production of pro-inflammatory mediators (including IL-6, IL1β and PGE2) were further estimated in vitro by ELISA in RAW 264.7 macrophages. [ABSTRACT FROM AUTHOR]

Introduction TLC bioautography for tyrosinase inhibitors has made recent progress; however, an assay with a relative low consumption of enzyme and quantitative capability would greatly advance the efficacy of related TLC bioautographic assays. Objective An improved TLC bioautographic assay for detecting tyrosinase inhibitors was developed and validated in this study. Methods L-DOPA (better water-solubility than L-tyrosine) was used as the substrate instead of reported L-tyrosine. The effects of enzyme and substrate concentrations, reaction temperatures and times, and pH values of the reaction system as well as different plate types on the TLC bioautographic assay were optimised. The quantitative analysis was conducted by densitometric scanning of spot areas, and expressed as the relative tyrosinase inhibitory capacity (RTIC) using a positive control (kojic acid) equivalent. Results The limit of detection (LOD) of this assay was 1.0 ng for kojic acid. This assay has acceptable accuracy (101.73-102.90%), intra- and inter-day, and intra- and inter-plate precisions [relative standard deviation (RSD), less than 7.0%], and ruggedness (RSD, less than 3.5%). The consumption of enzyme (75 U/mL) is relatively low. Two tyrosinase inhibitory compounds including naringenin and 1- O-β- D-glucopyranosyl-4-allylbenzene have been isolated from Rhodiola sacra guided by this TLC bioautographic assay. Conclusion Our improved assay is a relatively low-cost, sensitive, and quantitative method compared to the reported TLC bioautographic assays. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Introduction The needle trap device (NTD) technique is a new microextraction method for sampling and preconcentration of volatile organic compounds (VOCs). Previous NTD studies predominantly focused on analysis of environmental volatile compounds in the gaseous and liquid phases. Little work has been done on its potential application in biological samples and no work has been reported on analysis of bioactive compounds in essential oils from herbal medicines. Objective The main purpose of the present study is to develop a NTD sampling method for profiling VOCs in biological samples using herbal medicines as a case study. Methodology A combined method of NTD sample preparation and gas chromatography-mass spectrometry was developed for qualitative analysis of VOCs in Viola tianschanica. A 22-gauge stainless steel, triple-bed needle packed with Tenax, Carbopack X and Carboxen 1000 sorbents was used for analysis of VOCs in the herb. Furthermore, different parameters affecting the extraction efficiency and capacity were studied. Results The peak capacity obtained by NTDs was 104, more efficient than those of the static headspace (46) and hydrodistillation (93). This NTD method shows potential to trap a wide range of VOCs including the lower and higher volatile components, while the static headspace and hydrodistillation only detects lower volatile components, and semi-volatile and higher volatile components, respectively. Conclusion The developed NTD sample preparation method is a more rapid, simpler, convenient, and sensitive extraction/desorption technique for analysis of VOCs in herbal medicines than the conventional methods such as static headspace and hydrodistillation. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]