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Planta Med 2022; 88(01): 20-32
DOI: 10.1055/a-1326-2497
Natural Product Chemistry and Analytical Studies
Original Papers

Quantification of Silymarin in Silybi mariani fructus: Challenging the Analytical Performance of Benchtop vs. Handheld NIR Spectrometers on Whole Seeds

Authors

  • Sophia Mayr‡

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria

  • Simon Strasser‡

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria

  • Christian G. Kirchler

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria

  • Florian Meischl

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria

  • Stefan Stuppner

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria
    2   ADSI – Austrian Drug Screening Institute, Innsbruck, Austria

  • Krzysztof B. Beć

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria

  • Justyna Grabska

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria

  • Sonja Sturm

    3   Institute of Pharmacognosy, University of Innsbruck, Innsbruck, Austria

  • Hermann Stuppner

    3   Institute of Pharmacognosy, University of Innsbruck, Innsbruck, Austria

  • Michael A. Popp

    4   Michael Popp Research Institute of New Phyto Entities, University of Innsbruck, Innsbruck, Austria

  • Günther K. Bonn

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria
    2   ADSI – Austrian Drug Screening Institute, Innsbruck, Austria

  • Christian W. Huck 

    1   Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innsbruck, Austria

Supported by: Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie 402.000/0017
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Abstract

The content of the flavonolignan mixture silymarin and its individual components (silichristin, silidianin, silibinin A, silibinin B, isosilibinin A, and isosilibinin B) in whole and milled milk thistle seeds (Silybi mariani fructus) was analyzed with near-infrared spectroscopy. The analytical performance of one benchtop and two handheld near-infrared spectrometers was compared. Reference analysis was performed with HPLC following a Soxhlet extraction (European Pharmacopoeia) and a more resource-efficient ultrasonic extraction. The reliability of near-infrared spectral analysis determined through partial least squares regression models constructed independently for the spectral datasets obtained by the three spectrometers was as follows. The benchtop device NIRFlex N-500 performed the best both for milled and whole seeds with a root mean square error of CV between 0.01 and 0.17%. The handheld spectrometer MicroNIR 2200 as well as the microPHAZIR provided a similar performance (root mean square error of CV between 0.01 and 0.18% and between 0.01 and 0.23%, respectively). We carried out quantum chemical simulation of near-infrared spectra of silichristin, silidianin, silibinin, and isosilibinin for interpretation of the results of spectral analysis. This provided understanding of the absorption regions meaningful for the calibration. Further, it helped to better separate how the chemical and physical properties of the samples affect the analysis. While the study demonstrated that milling of samples slightly improves the performance, it was deemed to be critical only for the analysis carried out with the microPHAZIR. This study evidenced that rapid and nondestructive quantification of silymarin and individual flavonolignans is possible with miniaturized near-infrared spectroscopy in whole milk thistle seeds.

Key words

NIR - handheld spectrometer - silymarin - Silybi mariani fructus - Silybum marianum - Asteraceae

Supporting Information

    Voucher specimens for all 57 Silybi mariani fructus samples and wavenumber regions chosen for quantification with all spectrometers are available as Supporting Information.

  • Supporting Information (PDF)


Publication History

Received: 09 June 2020

Accepted after revision: 20 November 2020

Article published online:
12 January 2021

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