ATR-FTIR characterization and multivariate analysis classification of different commercial propolis extracts

Abstract

The chemical matrix of various bee propolis can vary significantly due to various factors like geographical origin. These differences in chemical composition impact the biological activities of bee propolis, highlighting the importance of accurate identification to ensure proper use in commercial products. This study discriminated commercial propolis-extracts used as air spray using their infrared spectra combined with multivariate analysis. Fourier transform infrared spectrometer with attenuated total reflectance (ATR-FTIR) was utilized to chemically characterize the propolis based on the absorption of constituent functional groups in the mid-infrared region. Differentiation of the propolis samples was achieved through principal component analysis (PCA) and hierarchical cluster analysis (HCA) using OriginPro 2024 software. Distinct peaks in the IR spectra included regions such as 3350–3250 cm⁻¹ (OH stretching), 2980 – 2870 cm⁻¹ (CH stretching), 1645 – 1635 cm⁻¹ (C=O stretching), 1140 – 1100 cm⁻¹ (CN stretching), and 1090 -1020 cm⁻¹ (CO stretching). PCA identified 1050 – 900 cm⁻¹ as the most significant wavenumber range for discriminating propolis samples. HCA clustered the samples based on the geographical origin of the raw propolis. The study suggests that FTIR spectroscopy in combination with multivariate analysis is a powerful tool in distinguishing different types of propolis incorporated in commercial products like propolis-extracts.