Quantification of phenolic acids by partial least squares Fourier‐transform infrared (PLS‐FTIR) in extracts of medicinal plants

Introduction Phenolic compounds are ubiquitous compounds found in all plants as their secondary metabolites. Phenols are becoming increasingly important particularly because of their beneficial effects on health. Objective To provide a faithful calibration model for the simultaneous determination an...

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Published in:Phytochemical analysis 2021-04, Vol.32 (2), p.206-221
Main Authors: Bensemmane, Nachida, Bouzidi, Naima, Daghbouche, Yasmina, Garrigues, Salvador, Guardia, Miguel, El Hattab, Mohamed
Format: Article
Language:English
Subjects:
Acids
ATR‐FTIR spectroscopy
Calibration
Comparative studies
Eugenol
Herbal medicine
Hydroxybenzoates
Infrared analysis
Infrared spectra
Infrared spectroscopy
Least squares method
Least-Squares Analysis
medicinal plant extracts
Medicinal plants
Metabolites
monoterpenic phenols
partial least squares (PLS) regression
Phenolic acids
Phenols
Plant Extracts
Plants, Medicinal
Pretreatment
Regression analysis
Secondary metabolites
Spectrometry
Spectroscopy, Fourier Transform Infrared
Thymol
Wavelengths
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Summary:Introduction Phenolic compounds are ubiquitous compounds found in all plants as their secondary metabolites. Phenols are becoming increasingly important particularly because of their beneficial effects on health. Objective To provide a faithful calibration model for the simultaneous determination and quantification of phenolic acids, as salicylic, vanillic, p‐hydroxybenzoic acids, eugenol and thymol in different extracts of medicinal plants, a comparative study was made between two methods of infrared measurements based on attenuated total reflectance (ATR) and transmission. Methods Characteristic absorbance peak heights of mid‐infrared spectra of individual phenolic acids were measured for the compounds. For partial least squares regression (PLS‐R) calibration mixtures of phenolic acids, wavenumber ranges, spectra pretreatment and number of latent variables, were assayed to improve the prediction capability of models using different spectral preprocessing techniques after mean centring of infrared data. Plant extracts were prepared by using water/methanol and ethanolic extraction solvents followed by Fourier‐transform infrared (FTIR)‐spectrometry analysis. The concentrations of phenolic compounds contained in the extracts were obtained by using the best models selected of the PLS calibration. Results PLS‐ATR‐mid‐infrared (MIR) measurement provided the most accurate results and offers a good methodology for the determination of phenolic acids. The analysis showed that the rate of phenolic acids and monoterpenic phenols in extracts of medicinal plants is in the same range obtained with the Folin–Ciocalteu method, which confirm that the developed method using PLS is therefore, highly specific and selective. Conclusion The simultaneous direct quantification of various phenolic acids in different plant extracts was possible with a fast and simple methodology based on PLS‐ATR‐FTIR analysis. This study offers a complementary tool to Folin–Ciocalteu reference method for the determination of phenols in extracts of medicinal plants. The potential of Fourier‐transform infrared (FTIR) spectroscopy, using attenuated total reflectance (ATR) and transmission measurements, has been exploited for the quantification of this type of analyte. The simultaneous direct quantification of various phenolic acids in extracts was possible with a fast and simple methodology based on partial least squares (PLS)‐ATR‐FTIR analysis without any additional treatment neither the use of any
ISSN:0958-0344
1099-1565
DOI:10.1002/pca.2974