Thin-layer chromatographic quantification of magnolol and honokiol in dietary supplements and selected biological properties of these preparations

Two isomeric biphenyl neolignans, magnolol and honokiol, are considered as constituents responsible for the healing effect of magnolia bark, a traditional Oriental medicine. To survey the increasing number of dietary supplements that contain magnolia bark or its extract, an affordable quantitative thin-layer chromatography (TLC) –densitometry method was developed. The methanol extracts were analyzed on the silica gel plates after manual sample application using n -hexane –ethyl acetate –ethanol (16:3:1, v/v/v) as a mobile phase. For quantitation, the chromatograms were scanned in the absorbance mode at the wavelength λ= 290 nm. The limits of detection and quantitation were 90 and 280 ng/zone for magnolol and 70 and 200 ng/zone for honokiol, respectively. None of the two targeted neolignans were detected in two of the six analyzed supplements. In the other four samples, the measured amounts were between 0.95-114.69 mg g −1 for magnolol and 4.88-84.86 mg g −1 for honokiol. Moreover, separations of these two neolignans on the TLC and high-performance TLC (HPTLC) layers were compared and HPTLC was combined with antioxidant (DPPH) and antibacterial ( Bacillus subtilis and Aliivibrio fischeri ) assays and mass spectrometry (MS), using the elution-based interface. Both magnolol and honokiol exhibited effects in all bioactivity assays. The HPTLC-MS tests confirmed purity of neolignan zones in the extracts of dietary supplements and supported tentative identification of the alkaloid piperine and the isoflavone daidzein as additional bioactive components of the investigated dietary supplements. Using the same mobile phase in the orthogonal directions 2D-HPTLC-MS experiments proved degradation, i.e., instability of magnolol and honokiol on the silica gel adsorbent

The 42nd Symposium Chromatographic Methods of Investigating Organic Compounds : Book of abstracts

The 42nd Symposium Chromatographic Methods of Investigating Organic Compounds : Book of abstracts. June 4-7, 2019, Szczyrk, Polan

Selected aspects of Modular Multilevel Converter operation

The operation of the Modular Multilevel Converter (MMC) is the main subject of this paper. Selected operation aspects are discussed on the basis of the averaged model, with a special focus on power section parameters and control. The direct modulation method has been chosen for the control of the MMC

ATP/EMTP study of ferroresonance involving HV inductive VT and circuit breaker capacitance

Ferroresonance is a phenomenon usually initiated by transients in power networks resulting from e.g. switching operations or ground faults. Non linear behavior of the core of an inductive voltage transformer results in magnetic saturation. long-lasting ferroresonant state is dangerous to the equipment due to prolonged overvoltage and large overcurrents in HV windings.in the present article numerical simulations of the ferroresonance phenomenon in a HV inductive Vare presented. the ferroresonant oscillations analyzed result from interaction between the voltage transformer and a grading capacitance of a circuit breaker

Accurate Location of Faults on Three-Terminal Line with Use of Three-End Unsynchronised Measurements

This paper presents a new fault location algorithm for three-terminal line utilising unsynchronised measurements of three-end currents and voltages. The distributed parameter line model is strictly considered for formulating three subroutines of the algorithm. Efficient procedure for selecting the valid results is introduced. The presented results of the ATP-EMTP evaluation prove the validity of the fault location algorithm and its high accuracy